4725.2250 GENERAL CASING REQUIREMENTS.
Subpart 1. Casing types. Permanent casing installed in a well or boring must be:
A. steel casing as specified in part 4725.2350;
B. stainless steel casing as specified in part 4725.6650 when used for a
monitoring well, environmental bore hole, or remedial well;
C. flush threaded polyvinyl chloride casing as specified in part 4725.6650 when
used for a monitoring well or environmental bore hole; or
D. plastic casing as specified in part 4725.2550.
Only two casing materials are allowed for use in all wells and borings: a minimum Schedule 40 (casings
10-inches and smaller) or standard weight (casings greater than 10 inches) steel pipe; and a minimum
SDR 21, 200 psi rated, solvent-welded plastic pipe. Monitoring wells and environmental bore holes may
be cased with flush-threaded casing (in addition to the other two types of casing) under certain conditions.
Monitoring wells, environmental bore holes, and remedial wells may be cased with stainless steel. Dug
water-supply wells must have standard casing; however, variances may be granted for larger diameter
casing made of other materials in some circumstances. The specifications and requirements for flush-joint
casing and stainless steel casing are located in Minnesota Rules, part 4725.6650. Certain exemptions exist
for temporary casing, outer casings, casings for flowing wells, and dewatering wells.
Subp. 2. Watertight casing required. All casing couplings and casing joints must
be watertight throughout their lengths. Casing must not have holes, cracks, or
separations.
Casing which has been slotted or perforated for use as a screen, is no longer considered to be casing, and
must meet the requirements and restrictions for screens.
Subp. 2a. Casing joints. All casing joints must be watertight, with threaded,
welded, or solvent welded joints, and comply with the standards in part 4725.2350,
4725.2550, or 4725.6650.
A. Threaded joints must have recessed couplings, reamed and drifted couplings,
or other couplings that match the design, taper, and thread type of the casing.
Thread must not be exposed on the pipe when the casing is joined.
B. Welded casing, except where an approved welding coupling is used, must
have beveled joints. The weld must extend the full circumference of the casing and
must completely fill the bevel.
C. Welding couplings must be made of material equivalent to the casing. The
upper and lower welds must extend the full circumference of the casing, and
completely fill the gap between the coupling and casing. Welding the casing to the
inside of the coupling is prohibited.
The only acceptable casing joints are threaded, welded, or solvent welded (“glued”). Other types of
joints such as splined, compression, compression gasket (Dresser coupling), slip, or cam-lock are not
approved except for some special casing connections as specified in Minnesota Rules, parts 4725.3350
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and 4725.4850. Different casing types or materials may not be used in the same casing string unless the
connection meets the criteria for both types of casing. As an example, a piece of threaded Schedule 40
steel casing may not be butt-welded to a piece of plain-end casing.
Welding rings or couplings that slip over both ends at a steel casing joint are allowed subject to the
conditions in item “C” above.
The use of plastic slip X slip couplings to join plastic casing to steel casing by friction fitting or gluing the
steel casing in the plastic fitting is not approved.
Recessed couplings have a shoulder or unthreaded lip which covers the pipe threads.
“Reamed and drifted” refers to the process of facing the end of the pipe to remove burrs and bevel the
end, and pushing a mandrel through the casing to maintain a minimum diameter. The term “reamed and
drifted coupling” refers to recessed couplings designed for use with reamed and drifted casing meeting
the ASTM A589 standard.
The threaded ends of the casing must be covered by the coupling when the pipe and coupling are made
up. “Standard” depth or “merchant” couplings are not approved.
Subp. 3. New casing required. Casing used in the permanent construction of a
well or boring must be new casing produced to the specifications of this rule part.
Casing salvaged from the same type of well or boring within 120 days of
installation is acceptable for reuse if it meets the specifications for new casing. A
potable water well must be constructed with new casing or casing salvaged from a
potable water well.
The specifications referred to are the requirements of this rule.
“Casing salvaged” means that casing has been removed from an unsuccessful or temporary well or
boring within 120 days of installation.
“New casing” means that the casing has not been used for well pipe, or for any other purpose. If a potable
water-supply well is cased with used casing, it must have been salvaged within 120 days of its installation
in a potable water well. If casing markings are unreadable on salvaged casing, the contractor may be
required to verify that the casing meets the specifications by laboratory testing.
Subp. 4. Casing markings required. Steel and plastic permanent casing except
flush-threaded PVC and stainless steel casing must be marked by the manufacturer
in accordance with casing specifications in parts 4725.2350 to 4725.2550.
Markings must be rolled, stamped, or stenciled by the manufacturer.
The rules require casing to be marked by the manufacturer, that is, the original producing mill.
However, if an end finisher has the legal right from a mill to mark casing, the mill documents this in
writing, and documents that the casing meets the ASTM or API standard, the pipe may be accepted.
194
If pipe appears not to meet the standard, the pipe will be rejected unless it is proven to the satisfaction of
the MDH or delegated well program that the pipe meets the standard by providing valid mill papers
and/or conducting testing by an independent testing lab. The costs of the testing are the responsibility of
the person wanting to use the pipe.
The ASTM and API standards require different markings for different types of casing. The marking
requirements are explained in the annotation after each material specification (Minnesota Rules,
parts 4725.2350 to 4725.2550).
Subp. 5. Casing testing. Casing rejected by the manufacturer must not be used.
The commissioner may require that casing be submitted to an independent testing
agency to evaluate if it meets or exceeds specifications when the casing:
Some casing manufacturers mark white or yellow circumferential bands on casing to indicate reject pipe.
However, the presence of painted bands does not always indicate that the pipe is reject.
A. lacks markings or has illegible or altered markings;
B. contains pits, cracks, patches, partial welds, bends, or other manufacturing
defects; or
C. lacks mill certification papers from the original manufacturer.
Subp. 6. Casing rejection. The commissioner shall reject casing for use in a well
or boring if:
A. the casing is not submitted for evaluation and verification when required by
the commissioner;
This refers to testing by an independent laboratory. The cost of testing the casing is the responsibility of
the person who wishes to use the casing.
B. the casing fails to meet the specifications in part 4725.2350,
4725.2550, or 4725.6650; or
C. the lot of casing contains defective lengths, including casing with girthwelded joints, or welded patches, or the lot has more than five percent of the
casings with lengths less than five feet.
Subp. 7. Temporary casing. Casing installed temporarily during drilling is not
required to meet the specifications for casing in parts 4725.2350, 4725.2550,
4725.6650, or this part except subparts 2, 7, and 16, but must be of sufficient
strength to withstand the structural load imposed by conditions both inside and
outside the well or boring, and free of oil or other contaminants. The casing must
be removed on completion of the well or boring.
Subpart 2 requires watertight casing, and subpart 16 requires a cap or cover.
195
This does not refer to “surface casing” or other pipe which is left in the ground. This only refers to casing
which is removed before the well or boring is completed.
Temporary plastic casing may be drilled through, however permanent plastic casing may not (Minnesota
Rules, part 4725.2650, subpart 8).
Temporary driven casing is not required to have a drive shoe.
Be aware that casing must not be removed and the hole allowed to collapse. A well or boring must be
sealed, or an annular space grouted, by pumping grout through a tremie pipe or the casing from the
bottom up. Casing can only be removed prior to grouting in a noncollapsing formation. If the formation
will collapse, the grout must be inserted before removing the casing.
If casing is not removed from the hole, it must meet the standards for permanent casing except as detailed
in subpart 9 below.
Subp. 8. Inner and outer casing. The inside diameter of an outer casing must be
at least 3.0 inches larger than the outside diameter of the inner casing, couplings,
or bell-end, whichever is larger, except that the inside diameter of an outer casing
must be at least 3.5 inches larger than the outside diameter of the inner casing,
couplings, or bell end, whichever is larger, for inner casings deeper than 100 feet
and larger than 12 inches inside diameter. The annular space between an inner
casing and an outer casing must be grouted for its entire length by pumping neatcement grout or cement-sand grout through a tremie pipe or through the casing as
specified in part 4725.3050. The inner casing must extend above the established
ground surface at least 12 inches.
This rule is designed to prevent the flow of contaminants or water in the annular space between casings.
The minimum annular space requirements are designed to allow sufficient space to grout with a tremie
pipe. Even though grouting through the casing is allowed, in certain circumstances it becomes necessary
to use a tremie pipe.
This rule formerly only allowed neat-cement grout between casings, now cement-sand grout is also
allowed.
The rule applies to all permanent casings including surface casings, “pit pipe” or “starter pipe” which are
not removed, liners, and protective casings. It does not apply to a screen leader pipe as defined in
Minnesota Rules, part 4725.0100, subpart 41h, or regulated in Minnesota Rules, part 4725.2750.
This rule requires that the annular space between multiple casings be entirely grouted with neat-cement
or cement-sand grout. Telescoped casing is prohibited. All casings must extend above the surface except
when a pitless is used, in which case the outer casing(s) may terminate immediately below the pitless. All
inner and outer casing combinations must meet the annular space requirements of this rule part.
For plain-end pipe, the smallest outer casing allowed is calculated by adding 3.0 inches to the outside
diameter of the inner casing. This number represents the minimum inside diameter of the outer casing. If
the inner casing is centered inside the outer casing, there will be 1.5 inches of grout between the casing.
For threaded and coupled, or bell-end casing, the smallest outer casing allowed is calculated by adding
196
3.0 inches to the outside diameter of the coupling or bell end. If the inner casing is centered inside the
outer casing, there will be 1.5 inches of grout between the outer casing ID and the couplings or bell ends.
If the inner casing is larger than 12 inches ID and is deeper than 100 feet, 3.5 inches, instead of
3.0 inches, is used. This will result in 1.75 inches of grout between centralized casings.
A table of common inner and outer casing combinations allowed by rule is included in the appendix.
The use of casing centralizers is no longer required. However, the use is permitted and generally
encouraged to further assure a competent seal and protect the casing from corrosion. Centralizers allow
for even placement of grout, but may interfere with insertion and removal of a tremie pipe.
Subp. 9. Outer casing in unconsolidated materials. A permanent outer steel
casing installed in unconsolidated materials is not required to meet the
requirements of this part except subparts 2, 9, and 17, or the material
specifications for casing in part 4725.2350 if the casing is of sufficient strength to
withstand the structural load imposed by conditions both inside and outside the
well or boring, the casing is free of oil or other contaminants, an inner casing
meeting the requirements of this chapter is installed, and the annular space
between the casings is filled with neat-cement grout, or cement-sand grout. The
outer casing must be installed in accordance with part 4725.3050 subpart 3 or 5.
This allows the use of permanent outer steel casing that does not meet the weight, thickness, or material
standard requirements of rule. Plastic casing is not allowed since it may not be drilled through (Minnesota
Rules, part 4725.2650, subpart 8). It is the contractor's responsibility to grout the space between the outer
and inner casing with neat-cement or cement-sand grout. The outside of the outer casing installed in
unconsolidated material must also be grouted (at least the top 50 feet, with the lower portion filled with
grout or cuttings) if installed by rotary or other methods which creates an annular space. If the lightweight
outer casing fails during installation or cannot be grouted, it is the contractor's responsibility to correct the
well or boring, including perforation, casing removal, or sealing if necessary.
Subp. 10. Casing inside diameter. The inside diameter of a permanent casing
must not be less than two inches for a well or boring greater than 50 feet in depth.
The 50-foot depth refers to the total depth of the well or boring, not the depth of the casing.
The rule is intended to allow sufficient space to perform maintenance; remove obstructions, test devices,
or pumping equipment prior to sealing; and properly seal the well or boring.
A well or boring less than 50 feet deep has no minimum casing diameter. However, access into the casing
for maintenance, repair, or sealing may be difficult. Ultimately the well or boring must be properly sealed,
which may require drilling out the casing if a grout pipe cannot be inserted.
Subp. 11. Casing height. A casing or casing extension must extend vertically at
least 12 inches above the established ground surface, the floor of a building (well
house) as specified in part 4725.2175, or a concrete slab, except that the casing for
a hand pump may terminate a minimum of 6 inches above a concrete slab in
accordance with part 4725.3250, item A, if the concrete slab is at least 6 inches
197
above the established ground surface. The established ground surface, slab, or
floor immediately adjacent to the casing must be graded to divert water away from
the casing. Termination of the top of the casing below the established ground
surface, such as in a well pit, is prohibited except that an outer casing may
terminate immediately below a pitless adapter installed on an inner casing.
All casings, except outer casings when a pitless is installed, or approved at-grade wells or borings, must
terminate a minimum of 12 inches above the established ground surface. The established ground surface
is the elevation of the actual or finished grade, whichever is higher. The ground or slab must be sloped so
that rain, surface water, spills, or floods run away from the well. If possible, the ground should slope
away from the casing in all directions.
Subp. 12. Casing offsets. Casing offsets are prohibited.
A “casing offset” means that a fitting or bend in the casing deviates the casing from being plumb and
aligned.
Subp. 13. Multiple casings. Except for inner and outer casings installed in
accordance with subpart 8, multiple casings must not be installed in a single bore
hole.
The rules require a casing to be surrounded with grout, cuttings in unconsolidated formations below
50 feet, or undisturbed formation in the case of driven casings. The practice of installing multiple casings
in a single bore hole with gravel pack surrounding screened intervals set at different depths does not meet
the standards of the rules. Each casing must be in a separate bore hole.
Subp. 14. Casing reduction and enlargement. A casing must maintain the same
inside diameter throughout the length of the casing, except that a larger diameter
pitless unit may be installed.
A casing must maintain the same inside diameter throughout the length of the well or boring and
terminate a minimum of 12 inches above-grade. It is not permissible to reduce or enlarge a casing, such as
connecting a 4-inch casing to a 4-1/2-inch casing, or other configuration. The only exceptions are that the
upper casing extension from the pitless to the surface may be increased in size. A “buried slab”
construction of installing a small diameter upper casing and pitless on a large diameter dug well is not
approved.
Subp. 15. Casing drive shoes. A drive shoe must be installed on driven casing
except for a drive point casing, temporary casing, or outer casing that has a neatcement or cement-sand grouted inner casing. The drive shoe must:
A. be made of steel or iron, with a hardened, beveled cutting edge;
B. have a wall thickness equal to or larger than the casing thickness, and
C. be threaded or welded to the bottom of the casing.
Use of a quality drive shoe can result in a good seal into rock, and may eliminate sand pumping and
crooked or bent casing.
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DRIVE SHOE REQUIREMENTS
● A coupling is not a drive shoe;
● Heat tempering the casing is not a drive shoe;
● A drive shoe must be as hard as the casing;
● A drive shoe may be commercially purchased or shop made; and
● Either a regular cable tool style or rotary style shoe (inner bevel versus outer bevel) is allowed.
DRIVE SHOE RECOMMENDATIONS
The rule does not have a minimum numerical standard for hardness, tensile strength, yield, bevel, or
length. However, it is recommended that a drive shoe have a:
● Rockwell C hardness of 50 or greater;
● Minimum 45,000 psi tensile strength;
● Minimum 25,000 yield strength;
● 30 degree bevel with a 1/16th inch face; and
● Length at least as long as the casing diameter up to 12 inches.
Subp. 16. Temporary cap or cover required. Until a well or boring is completed
and a permanent cap or cover installed, the installer must temporarily cap or
cover the bore hole, casing, and annular space of a well or boring when not
actively working on the well or boring, in accordance with subpart 17, or install a
weatherproof, tamper-proof cover. An overlapping steel plate is permitted. Tape,
pails, loose plastic, or similar covers are not permitted.
The casing must be temporarily covered during the construction process at times when actual work
on the well or boring is not occurring. The purpose is to prevent accidents such as children or animals
from falling in the hole, and to prevent surface contaminants from entering the well. In addition, the cover
will help prevent vandalism, and hole collapse should a large rain occur. Plastic pails, boards, or other
nonweatherproof covers are not allowed. In addition to the permanent caps and covers listed in rule
subpart 17, an overlapping metal plate may be placed over the casing, with the drill rods or drill string
used to hold the plate down.
An uncased hole must be covered during the construction process at times when actual work on the well
or boring is not occurring. A pit pipe covered with a cap or well seal may be used. The mud box may be
placed over the bore hole. An overlapping, competent metal plate or wood cover may be placed over the
uncased bore hole held down with the drill rods, or other heavy weight.
Subp. 17. Permanent cap or cover required. A permanent watertight and
vermin-proof cap or cover must be installed on the inner casing of a well or
boring. The cap or cover must be constructed of metal or plastic materials having
a thickness comparable to the casing requirements specified in subpart 1. The cap
or cover must consist of:
A. an overlapping cover or cap;
B. a threaded plug, cover, or plate;
C. a welded or solvent welded overlapping plate or cover;
D. an extension of the casing at least 1 inch into the base of a power pump; or
199
E. a sanitary seal or plug with a one-piece top plate, compression gasket, and
noncorrodible draw bolt(s). If the well or boring is in a building that meets the
requirements in part 4725.2175, a two-piece top plate, compression gasket, and
noncorrodible draw bolts may be used.
Caps must be constructed of materials comparable to the casing material standards.
See the comments after Minnesota Rules, part 4725.3150 for the details of pumps mounted on top of a
casing. The casing must extend at least 1 inch into the base of the pump. The casing must terminate at
least 12 inches above-grade or above a well-house floor.
The weatherproof and insect proof requirement applies to any connection through the cap or sanitary seal
including discharge connections, air lines, or electrical connections. Special emphasis should be placed on
electrical wires, see Minnesota Rules, part 4725.3150, subpart 3. Electrical wires must be sealed with a
compression gasket or other seal.
STAT AUTH: MS s 103I.101; 103I.111; 103I.205; 103I.221; 103I.301; 103I.401;
103I.451; 103I.501; 103I.525; 103I.531; 103I.535; 103I.541; 103I.621; 144.05;
144.12; 144.383; 157.04; 157.08; 157.09; 157.13
HIST: 17 SR 2773; 33 SR 211
4725.2300 [Repealed 17 SR 2773]
4725.2350 STEEL CASING REQUIREMENTS.
Subpart 1. General. Steel casing used in the permanent construction of a well or
boring must be new casing produced to:
A. ASTM Standard A53/A53M-04a;
B. ASTM Standard A589-96 (2001), Types I, II, and III; or
C. API Standard 5L-04.
Steel casing must have the minimum weights and thicknesses specified in the
table in subpart 2 subject to the tolerances in the specifications in this subpart.
The ASTM and API standards in subpart 1 contain criteria for such things as tensile strength, chemical
composition, and other characteristics of the pipe. Within the standards are numerous grades and weights
of pipe. Steel casing must meet the requirements of subpart 2 (Schedule 40 for casing 10 inches and
smaller, standard weight for casing larger than 10 inches) and one of the ASTM or API standards
(ASTM A53, ASTM A589, or API 5L). Subpart 2 details minimum wall thicknesses and standards for
threads and couplings.
Subpart 2 establishes nominal casing weight per foot and wall thickness for Schedule 40 and standard
weight steel pipe. Schedule 80 or heavier pipe is also acceptable. The ASTM and API standards allow
wall tolerance to vary from the nominal value in both the positive (thicker wall) and negative (thinner
wall). The minimum wall is - 12.5 percent under the nominal wall except for API pipe larger than 20 inch
(which is -10 percent).
200
The appendix contains an American National Standards Institute (ANSI) pipe schedule table.
Casing must be marked by the mill (or an approved process or end finisher, see below) in accordance with
the A53, A589, or 5L marking requirements.
REQUIRED MARKINGS ON STEEL CASING ACCORDING TO AMERICAN SOCIETY FOR
TESTING AND MATERIALS (ASTM) AND AMERICAN PETROLEUM INSTITUTE (API)
STANDARDS:
American Society for Testing and Materials (ASTM) STANDARD
A53M-04
Each length of pipe shall be legibly marked by rolling, stamping, or stenciling with the following
information:
1. The name or brand of the manufacturer;
2. The kind of pipe, continuous welded, electric-resistance welded A, electric-resistance-welded B,
seamless A; or seamless B; XS for extra strong, XXS for double extra strong;
3. The specification number;
4. The length in feet and tenths of a foot or meters to two decimal places;
5. When requested by the purchaser, Type S (seamless) and Type E (electric resistance welded) pipe
shall also be marked with the heat number; and
6. Seamless pipe shall be marked with Test Pressure, NDE (nondestructive electric test), or Test
Pressure/NDE.
For pipe with National Pipe Size (NPS) 1.5 (inches) and smaller, which is bundled, the above information
may be marked on a tag securely attached to each bundle.
NOTE:
The ASTM standard allows a processor to transfer markings on pipe which has been cut
into shorter lengths if all the information is transferred and if the name of the processor
is added. Minnesota rules, however, require that the marking be done by the
manufacturer. The MDH will allow a processor or end finisher to remark casing only if
the manufacturer (original producing mill) documents in writing that the casing meets
the specification, and that the processor has the right to mark the casing.
American Society for Testing and Materials (ASTM)
Standard A589-96 (2001), Types I, II, and III
Each length of pipe shall be legibly marked by rolling, stamping, or stenciling with the following
information:
1. The name or brand of the manufacturer;
2. Type number;
3. The kind of pipe (butt-welded, electric-resistance-welded, or seamless);
4. Grade;
5. Nominal or outside diameter size;
6. Wall thickness; and
7. The specification number and length (length shall be marked in feet and tenths of a foot or meters to
two decimal places).
Markings shall begin approximately 12 inches from the coupling of each length. Type II pipe NPS 1.5
and under and for all sizes of Type III pipe, the required markings as specified above may be applied to a
tag securely attached to the bundle or bale prepared for shipping.
201
NOTE:
The ASTM standard allows a processor to transfer markings on pipe which has been cut
into shorter lengths if all the information is transferred and if the name of the processor
is added. Minnesota Rules, however, require that the marking be done by the
manufacturer. The MDH will allow a processor or end finisher to remark casing only if
the manufacturer (original producing mill) documents in writing that the casing meets
the specification, and that the processor has the right to mark the casing.
American Petroleum Institute (API) Standard 5L-04
Pipe manufactured in conformance with this specification, shall be marked by the manufacturer with the
following information:
1. Manufacturer's name or mark;
2. Spec 5L;
3. Size in inches;
4. Weight per foot;
5. Grade (The grade specification is the actual marking for that grade, i.e. Grade A25 has the marking
A25. The grades are as follows: A25, A, B, X42, X46, X52, X56, X60, X65, X70, and X80. For
grades intermediate to X42 and X56, the symbol shall be X followed by the first two digits of the
specified minimum yield strength. For all grades X42 and higher containing columbium, vanadium,
and/or titanium, the grade symbol shall be followed by the letter(s) C, V, T or combination thereof.);
6. Process of manufacture (Symbols used are: seamless pipe (S), welded pipe which excludes buttwelded pipe (E), butt-welded pipe (F) and spiral weld pipe (SW).);
7. Type of steel (Symbols used are: electric-furnace steel (E) and rephosphorized steel class II (R). No
type marking is required for open-hearth or basic-oxygen steel.);
8. Heat treatment (Symbols used are: normalized or normalized and tempered (HN), subcritical stress
relieved (HS), subcritical age hardened (HA) and quench and tempered (HQ);
9. Test pressure; and
10. Length in inches and tenths of a foot.
Couplings shall be die stamped or paint stenciled and pipe shall be paint stenciled with the abovementioned required information.
For pipe 1.900 inch O.D. and smaller, the above markings shall be die stamped on a metal tag fixed to the
bundle, or may be printed on the straps or banding clips used to tie the bundle.
Seamless pipe greater than 1.900 inch O.D. and welded up to 16 inch O.D. shall be paint stenciled on the
outside surface of the pipe starting at a point between 18 and 30 inches from the end of the pipe, and in
the sequence as stated above, except when agreed between the purchaser and manufacturer some or all of
the markings may be placed on the inside surface in a sequence convenient to the manufacturer.
Welded pipe 16-inch O.D. and larger shall be paint stenciled on the inside surface of the pipe starting at a
point no less than 6 inches from the end of the pipe in a sequence convenient to the manufacturer, unless
otherwise specified by the purchaser.
202
Subp. 2. Steel casing pipe weight and dimensions.
S
c
h
e
d
u
l
e
4
0
S
t
a
n
d
a
r
d
W
G
T
Size
In
Inches
Plain
End
1
1-1/4
1-1/2
2
2-1/2
3
3-1/2
4
5
6
8
10
1.68
2.27
2.72
3.65
5.79
7.58
9.11
10.79
14.62
18.97
28.55
40.48
1.68
2.28
2.73
3.68
5.82
7.62
9.20
10.89
14.81
19.18
29.35
41.85
49.56
54.57
62.58
70.59
78.60
86.61
94.62
102.63
118.65
126.66
134.67
142.68
51.15
57.00
65.30
73.00
81.00
12
14
16
18
20
22
24
26
30
32
34
36
Wgt. Lbs. Per Ft
Thrds &
Thrds.
Cplgs.*
R&D Cplgs.
1.70
2.30
2.75
3.75
5.90
7.70
9.25
11.00
15.00
19.45
Thickness
In
Inches
Diameter-Inches
External
Internal
.133
.140
.145
.154
.203
.216
.226
.237
.258
.280
.322
.365
1.315
1.660
1.900
2.375
2.875
3.500
4.000
4.500
5.563
6.625
8.625
10.750
1.049
1.380
1.610
2.067
2.469
3.068
3.548
4.026
5.047
6.065
7.981
10.020
.375
.375
.375
.375
.375
.375
.375
.375
.375
.375
.375
.375
12.750
14.000
16.000
18.000
20.000
22.000
24.000
26.000
30.000
32.000
34.000
36.000
12.000
13.250
15.250
17.250
19.250
21.250
23.250
25.250
29.250
31.250
33.250
35.250
Thrds
per
Inch
11-1/2
11-1/2
11-1/2
11-1/2
8
8
8
8
8
8
8
8
8
8
8
8
8
Couplings
Minimum
External
Minimum
Diameter
Length
Inches
1.576
1.900
2.200
2.750
3.250
4.000
4.625
5.200
6.296
7.390
9.625
11.750
2-5/8
2-3/4
2-3/4
2-7/8
3-15/16
4-1/16
4-3/16
4-5/16
4-1/2
4-11/16
5-1/16
5-9/16
14.000
15.000
17.000
19.000
21.000
5-15/16
6-3/8
6-3/4
7-1/8
7-5/8
* Nominal weight based on length of 20 feet including coupling. Steel casing up to 10 inches in diameter must be Schedule 40. Larger diameter casing
must be standard weight.
Statutory Authority: MS s 103I.101; 103I.111; 103I.205; 103I.221; 103I.301; 103I.401; 103I.451;103I.501; 103I.525; 103I.531; 103I.535; 103I.541;
103I.621; 144.05; 144.12; 144.383; 157.04; 157.08; 157.09; 157.13
History: 17 SR 2773; 33 SR 211
203
STAT AUTH: MS s 103I.101; 103I.111; 103I.205; 103I.221; 103I.301; 103I.401;
103I.451; 103I.501; 103I.525; 103I.531; 103I.535; 103I.541; 103I.621; 144.05;
144.12; 144.383; 157.04; 157.08; 157.09; 157.13
HIST: 17 SR 2773; 33 SR 211
4725.2400 [Repealed, 17 SR 2773]
4725.2450 [Repealed, 33 SR 211]
The stainless steel standards formerly in this rule part are now in Minnesota Rules, part 4725.6650.
4725.2500 [Repealed, 17 SR 2773]
4725.2550 PLASTIC CASING AND COUPLING REQUIREMENTS.
Subpart 1. General requirements. Plastic casing and couplings used in the
permanent construction of a well or boring must:
A. meet ASTM Standard F480-02, except that flush threaded polyvinyl chloride
casing must not be used except for a monitoring well or environmental bore hole;
and
B. withstand internal pressures of 200 pounds per square inch (psi). Standard
dimension ratios (SDR) and water pressure ratings (PR) at 23 degrees Celsius (73
degrees Fahrenheit) for nonthreaded polyvinyl chloride (PVC) and
acrylonitrile-butadiene-styrene (ABS) plastic casing equal to or greater than 200
psi are as follows:
(1) pressure rating of PVC casing materials:
SDR
PVC 1120 PVC 1220 PVC 2112 PVC 2116 PVC 2120
13.5
315 psi
315 psi
200 psi
250 psi
315 psi
17
250 psi
250 psi
200 psi
250 psi
21
200 psi
200 psi
200 psi
(2) pressure rating of ABS casing materials:
SDR
ABS 1316 ABS 2112
13.5
250 psi
200 psi
17
200 psi
-
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The sources of the pressure rating in item B are the American Society for Testing
and Materials Standard D2241-04a “Standard Specifications for Poly(Vinyl
Chloride) (PVC) Pressure-Rated Pipe (SDR Series)” Table XI.I Standard
Thermoplastic Pipe Dimension Ratios (SDR) and Water Pressure Rating (PR) at
73 degrees Fahrenheit (23 degrees Celsius) for Nonthreaded Plastic Pipe; and
Standard D2282-99e “Standard Specification for Acrylonitrile-Butadiene-Styrene
(ABS) Plastic Pipe (SDR-PR),” Table XI.I Standard Plastic Pipe Dimension Ratios
(SDR) and Water Pressure Ratings (PR) at 73 degrees Fahrenheit (23 degrees
Celsius) for Nonthreaded ABS Plastic Pipe.
The commercially available plastic casing which meets both the F480 standard and the 200 psi
requirement is SDR 21 PVC in cell class 1120/1220, with solvent-welded bell and spigot joints.
“SDR” is the ratio of the pipe diameter to the pipe wall thickness. A smaller SDR is a thicker pipe. For
pipe of different sizes but the same SDR, the ratio of wall thickness to diameter remains constant. Pipes of
the same SDR and same material, but different diameters, have the same pressure rating.
ABS-well casing is covered by the standard but is generally not available.
Other casing joining methods such as flush-threaded, threaded and coupled, splined, and cam-loc, are not
known to be made which meet the standards, except that flush-threaded pipe is allowed for monitoring
wells and environmental bore holes under limited conditions, see part 4725.6650.
REQUIRED MARKINGS ON PLASTIC WELL CASING
American Society for Testing and Materials (ASTM) F480
Plastic well casing pipe shall be marked at least every 1.5 m (5 feet), in letters not less than 5 mm
(3/16 inch) high in a contrasting color with the following information:
1. Nominal well casing pipe size (for example, 5 inches);
2. Well casing pipe standard dimension ratio (for example, Standard Dimension Ratio 17);
3. Type of plastic casing pipe material (for example, ABS or PVC);
4. The wording “well casing” followed by the impact classification (for example, IC-3);
5. Designation “ASTM F480” including the year of issue of the standard with which the well casing
pipe complies;
6. Manufacturer's name or trademark;
7. Manufacturer's code for resin manufacture, lot number, and date of manufacture;
8. The seal or mark of the laboratory making the evaluation of the plastic for potable water use spaced at
intervals specified by the laboratory; and
9. Pressure rating (must be 200 psi or more).
205
Subp. 2. Additional approved fittings and couplings. In addition to the plastic
couplings approved under subpart 1, the following fittings and couplings may be
used to connect a steel pitless unit or screen to plastic casing:
A. fittings or couplings with socket dimensions meeting the requirements of
ASTM Standard F480-02, Table 3 and having a water pressure rating of at least
200 psi;
B. Schedule 40, slip x internal thread fittings, four-inch and smaller meeting the
requirements of ASTM D2466-02; or
C. Schedule 40, slip x internal thread fittings and slip x external thread fittings,
five-inch diameter meeting the requirements of ASTM D2466-02.
Except for couplings to join plain-end pipe together by solvent welding, PVC manufacturers are not
currently making fittings meeting the F480 standard because of the relatively small well market. Since
some necessary fittings are not made, the rule has been amended to allow some equivalent fittings
manufactured for potable water piping (plumbing).
In addition to couplings which meet all the requirements of ASTM F480, the rules allow couplings that
are manufactured to meet the dimensions of ASTM F480 and have a 200 psi rating. In addition, a 4-inch,
Schedule 40, PVC, “transition” fitting from solvent welded to internal threads is approved; and a 5-inch,
Schedule 40, PVC transition fitting from solvent welded to either internal or external threads is approved.
“Deep socket” Schedule 40 (PVC1120, PVC1220, or PVC2120), NSF potable-water approved, 4-inch,
and smaller slip X slip couplings are approved for solvent welding two pieces of plain end plastic casing
together. The practice of using this coupling to connect steel casing to plastic casing is not approved.
Standard “shallow” slip X slip couplings are not approved.
Nonthreaded PVC couplings greater than 4 inches in diameter must meet all of the ASTM F480 standards
or the standards of ASTM F480 Table 3 and be:
● Schedule 80 up to 12 inches in diameter if made of PVC1120, PVC1220, or PVC2120;
● Schedule 80 up to 8 inches in diameter if made of PVC2116; or
● SDR 21 if made of PVC1120, PVC1220, or PVC2120.
Subp. 3. Compliance with ANSI/NSF standard required. All plastic casings,
couplings, components, and related joining materials including solvents, cements,
or primers used in the construction of a well or boring must conform with the
requirements of ANSI/NSF Standard 61-2003e or the health effects portion of
ANSI/NSF Standard 14-2003 and be tested as conforming by an agency certified
by the ANSI. Conformance to the ANSI/NSF standard must be coded, stamped, or
marked on the casings, couplings, components, and related joining materials
including solvents, cements, or primers.
206
Products certified to conform to ANSI/NSF standards must bear the mark of the testing agency certified
by the ANSI. Standards 61 and 14 were developed by NSF International (formerly the National Sanitation
Foundation), and approved by ANSI/NSF International. NSF both develops standards and tests materials
to determine if they meet the standard. While NSF International is currently the largest organization
testing products for compliance with Standards 61 and 14, other organizations can be, and are, accredited
to test products.
At the present time, NSF International, Underwriters Laboratory (UL), the Water Quality Association
(WQA), the International Association of Plumbing Mechanical Officials (IAPMO), and CSA
International also tests products for compliance. Materials that meet the ANSI/NSF standard must be
marked with the insignia of the certified testing organization. For example, the NSF mark is a rectangular
label or plate with “NSF” in a circle and the product trade designation number. For products where the
label is not feasible or practicable, a block with the letters “ANSI/NSF” followed by the standard number
is used. Materials meeting ANSI/NSF Standard 61 would be marked “ANSI/NSF-61.” Plastic piping
components certified under Standard 14 are marked “pw” for potable water, or “wc” for well casing.
STAT AUTH: MS s 103I.101; 103I.111; 103I.205; 103I.221; 103I.301; 103I.401;
103I.451; 103I.501; 103I.525; 103I.531; 103I.535; 103I.541; 103I.621; 144.05;
144.12; 144.383; 157.04; 157.08; 157.09; 157.13
HIST: 17 SR 2773; 33 SR 211
4725.2600 [Repealed, 17 SR 2773]
4725.2650 PLASTIC CASING INSTALLATION.
Subpart 1. General. When preparing to install plastic casing, a person must:
A. inspect casing and couplings carefully for cuts, gouges, deep scratches,
damaged ends, and other major imperfections, and not use any plastic casing or
coupling having such defects or imperfections;
B. use solvent cement meeting the requirements of the specifications for the
plastic that will be used;
Solvent cement manufactured for use with ABS pipe must not be used for PVC pipe.
C. use only casing and coupling combinations that give interference fits;
“Interference fit” means that the pipe socket (bell end) is tapered. The pipe outside diameter is equal to
the socket inside diameter at a point approximately one-third from the socket bottom. This results in a
tight fit of pipe to socket.
D use plastic couplings with molded or formed threads and thread lubricants
suitable for the plastic material that will be used; and
Threads must be molded or formed in the manufacturing process, cut threads are not approved. Threaded
and coupled well casing meeting the ASTM F480 Standard is generally not manufactured.
207
E. use a coupling appropriate for the specific transition intended when a
nonplastic screen is attached to a plastic casing.
Screens may be threaded or solvent welded to the casing or may be telescoped into the casing with a
nontoxic packer.
Subp. 2. Cutting. When cutting plastic casing, casing ends must be cut square
using fine-tooth blades with little or no set or a plastic pipe cutter equipped with
extra wide rollers and thin cutting wheels. Standard steel pipe or tubing cutters
must not be used for cutting plastic casing.
Plastic casing is extremely brittle when cold. Cutting plastic casing in winter must be done with caution.
Subp. 3. Cleaning. All dirt, dust, moisture, and burrs must be cleaned from
casing ends and couplings using chemical or mechanical cleaners suitable for the
particular plastic material. All burrs must be removed.
Subp. 4. Primer. A primer must be used when the type of solvent cement
used requires one.
Subp. 5. Cementing. An even coat of cement must be applied to the inside of the
couplings to cover the distance of the joining surface only. An even coat of solvent
cement must then be applied to the outside of the casing being joined to a distance
equal to the depth of the casing coupling socket.
Solvent cements contain Volatile Organic Chemicals (VOCs) such as acetone, tetrahydrofuran, methyl
ethyl ketone, and others. Application of excessive cement does not improve joint strength and may lead to
VOC contamination of the water. Over application may also create a ridge that will interfere with
installation of a pump.
Subp. 6. Assembling. When assembling plastic casing, a person must:
A. make the joint with solvent cement before the solvent cement dries;
B. reapply cement before assembling if the solvent cement dries partially;
C. turn the casing to evenly distribute the solvent cement while inserting the
coupling into the coupling socket;
D. insert the casing to the full depth of the coupling socket and assemble
casing;
E. remove excess solvent cement from the exterior of the joint with a clean, dry
cloth;
F. tighten a threaded joint by no more than one full turn using a strap wrench;
This means that after the joint is hand tight, a strap wrench (not a pipe wrench) is used to tighten the joint
no more than one turn. Over tightening may crack the joint.
208
G. not disturb the coupling joint until after the solvent cement has set; and
H. allow sufficient time for the solvent cemented joint to set.
The amount of time necessary for adequate joint set is dependent on pipe diameter, solvent type,
temperature, and humidity. Large diameter pipe, low temperature, and high humidity slow set times.
Recommended set times are found in the appendix of earlier versions of the ASTM F480 standard, and
can be many hours.
Subp. 7. Screws. Screws must not be used to join plastic casing.
Solvent welded bell and spigot, or threaded joints are the only connections allowed between plastic
casings. Rivets, bolts, screws or any other type of fasteners are not allowed for connecting plastic casing.
These devices actually weaken the joint, and may allow leakage of contaminants into the well or boring.
Screws may not be used to join plastic casing, regardless of the type or length of the screws, or the depth
of the hole drilled into the bell end.
Subp. 8. Drilling inside permanent plastic casing prohibited. A person must not
drill inside permanent plastic casing. Drilling tools such as drill bits must not be
inserted in plastic casing. This prohibition does not include the installation or
repair of screens or development of the well or boring.
The reason for this requirement is to prevent damage to the plastic casing from drilling tools. All types of
drilling tools are prohibited from insertion or use inside a permanent plastic casing. Permanent plastic
casing may not be drilled through. Plastic casing may not be installed over drilling tools already in the
hole. This does not prohibit the insertion of bailers, jetting tools, pumps, or other equipment to develop a
well, nor does it prohibit the insertion of a tool such as a taper tap to remove a screen. This also does not
prohibit drilling through a temporary plastic pit pipe or surface casing if the casing is removed. Tools
used for development, screen placement, screen retrieval, or setting a pump may be inserted in plastic
casing. Development of a well or boring with air through drill rods is allowed as long as a drill bit is not
connected to the drill rod. These activities are permitted since there are no reasonable alternatives;
however, they can damage the casing if not carefully done.
Subp. 9. Limestone, dolomite restriction. Plastic casing must not be used as an
outside casing in wells and borings cased more than five feet into limestone or
dolomite bedrock. In limestone and dolomite bedrock, plastic casing may be used
as an inner casing if surrounded for the entire length, by an outer steel casing.
Limestone and dolomite are rocks comprised of calcium and magnesium carbonate. Further explanation is
found in Minnesota Rules, part 4725.1851.
This rule was established to prevent casing deformation due to the heat of hydration from cement grout.
Neat-cement or cement-sand grout is required in bedrock. Limestone or dolomite may have large
fractures, solution cavities, and even caves. Cement grout in a large cavity may generate sufficient heat to
deform or melt plastic casing. Bentonite grout is not an acceptable alternative since it will not support the
casing and may wash away in karsted formations.
209
Diagrams of plastic casing construction are included in the grouting section, Minnesota Rules,
part 4725.3050.
Subp. 9a. Plastic cased wells or borings completed in bedrock. A plastic cased
well or boring completed in bedrock, whether screened or open hole, must be
cased into the bedrock a minimum of five feet and the annular space surrounding
the casing in bedrock must be filled with neat-cement grout or cement-sand grout
according to part 4725.3050, subpart 7.
The rules do not allow the interconnection of an aquifer in unconsolidated sediments with an aquifer in
bedrock. When a well or boring is completed in bedrock below unconsolidated sediments it is necessary
to cement the annular space since the plastic cannot be driven, and a hole larger than the casing must be
drilled in order to install the casing. Bedrock must be grouted with neat-cement or cement-sand grout.
Subp. 10. Driving prohibition. Plastic casing must not be driven. Use of a drive
shoe with plastic casing is prohibited.
Forcing plastic casing in the ground may deform the casing.
Subp. 11. Sealing, removal, or replacement. A person installing plastic casing
must either seal a well or boring or remove and replace all casing when:
A. the plastic casing cannot be installed without driving the casing;
B. a screen or pump cannot be installed without force; or
C. the casing fails during construction or pumping of the well or boring.
Plastic casing does not have the strength or collapse resistance of steel casing. Boulders, improper
grouting, crooked holes, or excessive depth and low water levels may cause damage to the casing. This
rule subpart establishes that the contractor is responsible for damage or errors of installation.
STAT AUTH: MS s 103I.101; 103I.111; 103I.205; 103I.221; 103I.301; 103I.401;
103I.451; 103I.501; 103I.525; 103I.531; 103I.535; 103I.541; 103I.621; 144.05;
144.12; 144.383; 157.04; 157.08; 157.09; 157.13
HIST: 17 SR 2773; 33 SR 211
4725.2700 [Repealed, 17 SR 2773]
210