Grey Water

Grey Water systemGrey water is defined as the waste water from showers, basins, kitchen sinks and washing machines. E.g all waste water other than from the toilet. The Auckland Council policy on grey water is identical to that for black water in that it must be collected in a septic tank. The only difference is that a grey water tank can be 3,300 litre as compared with 4,500 litre for a full system although the size required is dependent on the water use of the home. It must be and distributed to ground through a compliant land application system. It is not compliant to recycle it without treatment as it could contain faecal bacteria as well as soaps, cleaners and anything else that goes down the kitchen or bathroom sink. That being the case, it makes sense that you install one wastewater system which treats both grey and black water.

There are systems where you can recycle grey water for use in your toilet flush system but in this case the grey water has to be collected, filtered chlorinated and UV treated before it can be recycled as toilet water. A toilet can use from three litres to eleven litres of water with each flush so it makes good sense, especially if you are dependent on rain water, to recycle your grey water to become your toilet black water. Some sort of electric pump system would be required to recirculate the treated grey water.

Once the grey water is collected within the 3500 litre septic tank it can be filtered and then discharged to ground through dripper lines which must be pressure dosed. This would need an electric pump to generate the pressure required though it could be gravity fed provided you had approximately 16m of fall between the tank and the land application area. Because of the bacteria and chemicals in grey water, such as soaps, washing powder, and cleaning fluids, it is not recommended to use such a system to irrigate a vegetable garden.

Because each site is different, each grey water system design needs to take into account the personal habits of the users, the quantity of waste water generated, the size of the site, the soil category, and how it will be recycled. Any system needs to be compliant with Auckland Councils TP58 (page 116) rules for waste water distribution.

Septic system example cost

Septic system installations require consent. Ask your plumber or contact the Auckland Council.

Septic System

Basic septic system.


Engineer design



Total Cost

Including GST.


Septic Waste Removal

Septic Tank Sucking

Removal and disposal of 3500l of septic waste.



DCL Contractors

Septic tank cleaners and waste removal.

Ph:09 4290 417

Great Barrier Plumbing & Drainage

Certified Plumber, Drainlayer, and Licensed Gasfitter.

Ph:09 4290 298
Mob: 027 429 0298

Trevor Lyon

Certified Plumber and Drainlayer.

Ph:09 4290 316

Last updated on the 06-04-2020