Greywater Retrofit in the Perth Hills in a non-sewered area
This case study describes a greywater reuse system that was retrofitted to an existing 4 bedroom, single story, brick-on-concrete slab house on a 1,000 m² non-sewered block in the Perth hills. Both laundry and bathroom greywater was diverted from the wastewater stream into a greywater diversion system to provide irrigation for lawn and gardens.
The design professional had to ensure pipework was sized correctly to comply with Plumbing Regulations. Appropriately sized Drainage, Waste and Vent (DWV) pipe was used where the greywater diversion device was close to the greywater sources. Greywater collected from the en suite had to travel further and required the use of 100mm DWV pipe.
Greywater System make and model
The GRS-H Filter system from Water Installations, Mundaring is used to filter greywater for whole of house diversion from bathroom/laundry, removing any hair or lint before passing into the infiltration area. Fibre filter bags 500mm long are used and if blocked or too much water enters, a safety overflow device is fitted to direct greywater to the existing sewer or septic tank system as required.
The manifold system used in this greywater case study includes a Biomatt filter and KRain switching device. The Biomatt traps coarse material, such as hair, which may inadvertently pass through the main filter body and be pumped out.
Valve Box & Pump Pit
The filter body is protected by a large valve box (with purple cover) and the lid for the pump pit is foot trafficable.
Cleaning of the filter should occur fortnightly or weekly if excessive laundry and bathroom use has occurred. This device redirects wastewater from the existing system to a disconnector gully return or directly to sewer via a reflux valve.
The previous image demonstrates the filter body before the pump pit and the overflow pipework to the existing septic tank system. Overflow was sent to a Disconnector Gully (DG, or trap) – seen in front of the black pump pit – which was also charged by a single hand basin. A DG is required for at least one fixture so that any backup from the sewer or septic tank system can escape and pass outside of the house.
Greywater Irrigation area
Lawn 70m² and gardens 30m² = total of 100 m². This was laid out as two separate zones as different dripline was used in each area:
- Tiran dripline was used for the garden areas and trees as it is non pressure- compensating. Each dripper emits 8 L/hr.
- Netafim XR dripline was used for the lawn irrigation, as it is pressure-compensating. Each dripper emits 2 L/hr and is impregnated with a copper compound to prevent root intrusion,
A K-Rain indexing valve was installed to automatically switch from one zone to another each time the pump was activated.
K-RAIN SWITCHING DEVICE
The manifold system used in this greywater case study includes a Biomatt filter and K-Rain switching device.
Cost of installation of a Greywater System
Approximately $7,000 which included the complete system, all labour, plumber’s charges and power point installation, all irrigation to lawn and garden beds, Council fees and inspection, testing and commissioning, and handover to client.
Approvals process for Greywater
Approximately three weeks from contract signing to handover. This included a couple of weeks for local government “approval to construct”, one day to install the greywater unit with all plumbing and electrics and one day to install the irrigation system, test and commission. Council inspection was arranged for another time and day and handover and training to the clients took place soon after.
Annual water savings
Outcome/Water savings from using a Greywater System
A family of four occupy this house. Based on the Department of Health allowance of 100L/person/ day approximately 400L of greywater could be produced daily, throughout the year on non- rainy days, as system is switched off during rainy periods. Bureau of Meteorology (2019) state Perth receives an average of 80 days of rain, therefore maximum greywater produced (400L x 285 days) is approximately 114,000L (114kL) annually.
I love using Grey water in my garden because it allows me to minimise the use of scheme water in our garden watering regime with only small changes to the type of cleaning products we use in our laundry and bathroom. It also allows me peace of mind every time I take a shower knowing the water isn’t just going down the drain but directly into my beloved garden.
Sustainable Garden Design Perth
Having Greywater go to my garden means my plants get watered every day of the year when I’m home. The water savings in summer are huge. Installing a greywater system at my own new build was a must, along with a Rainwater tank. Putting these systems in during the build process is easy compared to retrofitting, and generally cheaper. ‘Water Capture’ sell, install and service Greywater systems in Perth.
WaterCraft service a lot of greywater systems across the metro area and see many gardens thriving on the use of greywater. Frequent watering with traces of soap and nutrients works really well for plants on poor sandy soils. But just as you wouldn’t expect your mains water retic system to run for years without any attention, don’t expect your greywater system to keep running without a service!