Domestic users are by far the biggest generators of wastewater due to the wide variety of uses of water in the home. The kitchen, bathroom, and toilet are the heaviest users of water, with toilet flushing consuming the most water.

Down pipe

Rainwater downpipe from gutter illegally connected to gully trap which allows rainwater into the wastewater system.

There are things you can do to help keep the wastewater system running smoothly from your house or business to the treatment plant where it gets treated.

Check your downpipes

You can help ensure the wastewater system runs efficiently by checking that your house roof downpipes are not being fed into a stormwater drain, not a gully trap.

When rainwater gets into the wastewater system from roof drain pipes it can quickly fill it up and prevent it from working properly.

Proper installation will ensure that your stormwater will not get into the wastewater network, which can cause overflows of untreated wastewater (sewage) during times of heavy rain.

This will avoid raw sewage waste flowing into rivers and spilling onto streets and private property.

Gully traps are the fittings that you can see outside bathrooms, toilets and kitchens that take wastewater from these rooms. 

Check your gully trap is not draining the area around it

Gully traps that are not set up correctly can allow stormwater runoff to enter them and into the wastewater system where it shouldn’t be.

The more of these that are like this at our houses and businesses, the more stormwater gets into our wastewater network causing problems like wastewater backing up onto properties and overflows to the environment.

Check that your gully trap isn’t in a low spot or flush with the ground surrounding it, if it is it may allow stormwater in during rain. To comply with the Building Code, it should be at least 25 mm above the surrounding ground level if the surrounding area is paved, or 100 mm above the ground level if it is unpaved.

There are gully trap surrounds that you can purchase from hardware stores, you just need to make sure you have the right size surround for your trap and that you seal it up to the ground and house so water can’t sneak past it. Alternatively you could talk to a drainlayer about raising the trap up.

Gully Traps

Before and after pictures of a low lying gully trap that could allow rainwater to be drained into the sewer system and upgraded with a new gully trap surround and sealed up to prevent inflow.

Avoid waste disposal units

Another way you can help the system work more effectively is avoiding installing waste disposal units or waste grinders where possible, as these put an extra load on the wastewater system with the volume of organic matter requiring decomposition. It is better to compost kitchen wastes or put them in your green organics bin. 

Minimise the fat that goes down the drain

Fat is the single biggest contributor to wastewater pipe blockages and dry weather overflows. It blocks household laterals and Council wastewater pipes and can be costly to unblock and clean up.

Fat is often poured down the drain while it is in its liquid form, but then starts to harden as it cools while travelling down it. Over time the fat layer becomes thicker and thicker, slowly clogging the pipe like fat in an artery.

Instead of pouring fat down the sink, you should put pans with fat aside and allow to harden, then scrape it out, or soak it up with paper towels and put in the green organics bin.

Businesses like restaurants have grease traps to capture this fat, which are cleared out regularly to minimise fat entering the wastewater network.

Minimise your use during rain

Rain water flooding drain

When rain is persistent and heavy over a long period of time the wastewater network can start filling up and eventually be overcome. At this point, wastewater can back up onto properties and overflows can occur.

Like all water authorities around the world, we have a problem with our wastewater systems called inflow and infiltration (I&I). This is when rain (stormwater) and groundwater makes its way into the wastewater network where it shouldn’t be.

Inflow is when rain gets in directly, like when roof downpipes are incorrectly drained into gully traps, or where gully traps are in low spots prone to flooding.

Infiltration is where groundwater leaks into buried wastewater pipes through joints or cracks.

I&I is most likely to happen during the peak wastewater use periods between 6am and 8:30am and between 4:30pm and 6:30pm (weekend morning peaks tend to be a little later). If you can avoid doing things like putting the washing on, or having a shower or bath during these times when there is prolonged rain, it will minimise the chance of overflows occurring.

A good rule of thumb is, that if there has been more than 30mm of rainfall in the previous 12 hours, then minimise your water use during peak periods.

We have an ongoing programme of investigations and physical works to reduce the problem of I&I in our wastewater network.

Industry responsibility

Industry can also assist by adopting cleaner production methods (waste minimisation) as well as onsite treatment of by-products where warranted. These measures can have a significant environmental benefit as many firms use large amounts of chemicals in their manufacturing process and the resulting by-products are then introduced into the wastewater system.

If you want to look into how your business might be able to improve its wastewater discharge or have ideas you would like to check, please call the Council to talk them over with the Trade Waste team who are keen on helping businesses to do their best.