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Inflow is rainwater or groundwater entering the wastewater network via a range of defects on public and private property.
Typical inflow sources may consist of:
Infiltration is when rainwater or groundwater drains into the ground enters the wastewater network. Ways that this can happen include:
The wastewater network is designed to only handle wastewater we all produce.Stormwater inputs limit how much our wastewater pipes can hold.
If enough stormwater enters the wastewater network it could cause issues like wastewater network overflows, sending wastewater onto people’s property and into the environment.
It can alsoinundate or effect the wastewater treatment plants, which could further increase the number of,or volume of overflows in the wastewater network, as well as reducing the level of treatment the wastewater receives before being discharged into the environment.
Flooding the network with inflow and infiltration also increases the cost associated with wastewater pumping and treatment.
This is not a new issue in Central Hawke’s Bay, but it is something council must address to reinforce durable infrastructure and allow for smart growth.
We have set aside funding in our Long Term Plan (LTP) to address this issue. In the current LTP period, we have been supported by Central Government by securing Central Government funding from the Three Waters Reform programme for this project. This has meant we have been able to invest more resources into investigation of our network.
Other actions we are taking include:
We are using CCTV cameras to identify any leaking pipes
Inspecting manholes for any defects
Looking at private properties to identify pipes sending stormwater into the wastewater network
Fixing issues with existing assetse.g.jetting pipes to clear infiltration and fat build up, replacing or sealing broken pipes and manholes.
When we find a defect, or someone reports an overflow, we are fixing, repairing, or replacing pipes and manholes. Our scheduled pipe renewals also play a part in this. Find out more about our renewals programme here: https://www.chbdc.govt.nz/our-district/projects/bigwaterstory/chb-water-renewals/
Monitoring flows
Flow monitoring studies, and hydraulic modelling of the network helps us determine where stormwater comes from and how much flow there is. We also investigate issues that arise on the network that can help pinpoint where stormwater is entering.
Look at the stormwater and wastewater connections on your property. If you find any defects, there are steps to take to fix them and ensure everything is running correctly.
Defect |
What the defect causes |
Remedy |
Downpipe connected to gully trap |
Stormwater will enter wastewater network |
Connect downpipe to appropriate stormwater outlet
|
Downpipe to ground |
Water ends up ponding on the ground, and can end up under the house, resulting in rising dampness |
Connect downpipe to appropriate stormwateroutlet |
Gully trap level with the ground |
Ponding water can overtop into the gully traps because the sides are not high enough |
Raise gully trap or put sealed barrier around the gully trap. Gully traps should be raised 10cm from the ground
|
Cracked or leaking gully trap |
Ponding water can get into gully trap |
Replace gully trap |
Terminal vent missing cover |
Vermin can get into your wastewater pipes |
Protect your terminal vent with a vent pipe cover |
No spouting, leaky spouting |
Water ends up ponding on the ground, and can end up under the house, resulting in rising damp The water can also end up getting into the pipework on your property if ponding occurs in the same area as the pipework |
Install spouting and downpipe, connect to appropriate stormwater outlet |
Broken downpipe |
Allows stormwater to spill onto ground with the same impact as the downpipe to ground |
Fix the broken downpipe |
No back on gully trap |
Ponding water can get into gully trap
|
Install a new concrete surround, or replace gully trap |
Covered gully trap |
Covered gully traps mean sewage might back up into the house The gully trap is an overflow point. If the lateral to the Council network becomes blocked, the wastewater would normally come out the gully trap. By covering it, the wastewater would come out the next lowest point |
Educate residents to let them know why they shouldn’t cover them |
Please let us know if you spot any overflows from the wastewater network. These can be caused by stormwater getting into the network or a system blockage, which requires immediate attention.
Contact your local plumber or drainlayer if you find a defect on your property. They will determine if there is a problem on your propertyor inournetwork.
If you are unsure if you have a defect, you can send us a picture via our Send Snap Solve App, and we can advise.
You can also contact our team atcustomerservice@chbdc.govt.nz or call us on 06 857 8060.
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