Grey water treatment systems

Most of us now know about being able to use grey water on the garden, but what may not be as widely known is that it's also possible to make use of it inside the home, for example in toilets and washing machines.

Any standard water tank – i.e. an in-ground, bladder or poly tank – can be used to store grey water. It's illegal to keep untreated grey water for more than 24 hours - this is where grey water treatment systems come into play. "We recommend a natural grey water treatment system," says Sue from grey water recyclers and rainwater tank manufacturers New Water. "The only chemical involved is bromine, which is very similar to chlorine – that's just for the final 'polishing' of the water. It can then be stored indefinitely in a tank." 

The components of the treatment systems are the system itself plus two tanks (one of these will be for the grey water). Treatment systems take water from the household (except for that from the toilet and the kitchen) and the water is then diverted to a storage tank where it's left to settle for 12 hours. It then gets pumped into the treatment system, where it goes through a process of aeration and filtration. Next it feeds over the bromine dosing unit, and from there it goes into the storage tank, ready for use in the home.

These complex treatment systems require council approval. Your grey-water recycling company may be able to deal with that side of things for you, but be warned – there could be council fees involved (which can be up to $500). And not every region has the same regulations regarding grey water. "The rules differ from state to state – for instance, in Queensland there are some cases where you can't use the grey water above ground or in the home," says Sue. "It really depends on which government you're dealing with and which council you're dealing with."

Installing grey water treatment systems isn't cheap. The treatment system alone is likely to cost around $6800, and then on top of that you need the two tanks. In a new home, where the pipework can be tailored to the system from the outset, you might be looking at between $8000 and $10,000. For an existing home, where pipe diversion could be required, a system could cost up to $14,000.