Everything you need to know
about gully traps
Waste Pipes
Concrete
Surface
Grating
Ground Level
What is a gully trap?
25mm above
paved and 100mm
above unpaved
A gully trap is a basin in the ground which receives piped
wastewater from your kitchen, bathroom and laundry before it is
emptied into the sewer. The basin has a water seal to prevent foul
odours of the sewer reaching the surface. The top or surround is
raised above ground level to prevent stormwater and other foreign
matter entering the sewer. 600mm (max)
What should my gully trap
look like?
The diagram shows the accepted configuration of a gully trap as set
do not comply with this configuration are considered illegal. Compacted granular
bedding material
The Building Code says your gully trap surrounds must be 25mm
above a paved surface or 100mm above unpaved surfaces.
Gully traps are not
meant for stormwater
Separation from building material
Approved gully trap keeping rain water
out of the wastewater system.
Water seal
65mm (min)
out in the New Zealand Building Code. Gully trap arrangements which
Illegal gully trap allowing rain into
the wastewater system.
In periods of heavy rain, a sudden increase in water
flowing into the sewer through gully traps can result
in wastewater overflows elsewhere in the sewerage
system. This can result in raw sewage entering
our harbour. These excessive flows can also cause
problems at the wastewater treatment plant due to
system overloading.
Common reasons why rain water flows into a gully trap include:
• Incorrect height of the gully trap surrounds
• Downpipes plumbed into the gully trap instead of the stormwater system
A TAURANGA CITY COUNCIL SERVICE
• Landscaping that directs water into the gully trap
Preventing sewer overflows
to keep our harbour clean
The Southern Pipeline is a $106M wastewater pipeline
that will redirect most of the city’s wastewater over to
Te Maunga. However, it’s still a few years away.
In the meantime Council has started inspecting gully
traps throughout the city to help customers know if
theirs is OK, and to offer advice on how to fix them if
they’re not.
If every property owner with an incorrectly designed
gully trap fixed it, the amount of stormwater sneaking
into the wastewater system would be greatly reduced.
Not all problems will be
solved by these options . . .
If you have landscaping that directs stormwater
into your gully trap, you may need to speak to your
drain layer about options to fix this. Some gully
traps may also need additional work to make them
How can I fix my
gully trap?
compliant.
To further minimise any water getting into the
wastewater system all property owners must
ensure that:
To raise your gully trap to the required height,
• any paving surrounding the gully trap is graded
to direct all stormwater away from it
suitable.
• all waste pipe connections to the gully trap
remain water tight
here are a couple of low cost options that may be
1. Install a plastic riser. This is fitted over the
gully trap with sealant around the edges and
wall to keep stormwater out of the gully trap.
These are available from hardware outlets
• any downpipes that currently discharge into
the gully trap are redirected to a stormwater
system (e.g. soak hole or reticulation system).
like Mitre 10, Placemakers or Carters.
2. Install a concrete half ring (also known as a
nib wall). This is cemented into place with
stormwater out of the gully trap. These
are available from a concrete supplier like
Humes.
For more information or advice,
please contact Tauranga City
Council on (07) 577 7000 or go
to www.tauranga.govt.nz and
type in key words ‘gully trap’.
A TAURANGA CITY COUNCIL SERVICE
If you need more help contact Waterline
Ph: 577 7000 Web: www.tauranga.govt.nz
MVM 50675 F
sealant around the edges and wall to keep