Sunday, February 17, 2013

Grey water installed

After years of thinking about installing grey water we finally did it. We had a bit of spare money and the thought of having a guilt free lawn and a more sustainable water source for our productive trees was irresistible.

Firstly, what is grey water? Usable grey water is water from bathrooms (shower, bath and sink) and laundries (washing machine and trough). It does not include water from toilets and kitchen water (known as black water). I asked Josh Byrne to recommend a system which was a low power user and fairly low maintenance. He said we should get a Grey Flow system so I looked into it and it sounded good. The systems are made by a local company called AWWS. Grey Flow systems are diversion systems with no holding tank. This means they are fairly simple and low maintenance. Our system was installed by Mark Harland of Water Capture and I thoroughly recommend him. Here's how it works:

We cut into our bathroom and laundry discharge pipes and diverted them to a chamber. Inside the chamber is a float valve and pump, when water gets to a certain level the pump sends the water through a filter and out to a rotor valve. This operates hydraulically (no power use) to direct water to up to six zones of our garden. It pumps 100 litres per station before switching to the next.  Then the water goes to dripline piping, either subsurface (for lawn) or sub mulch (for trees and shrubs). If power goes out the system automatically sends water to the main sewer. The main proviso is that the water is not used on herbs or vegetables due to the health risk. Also washing products such as shampoo, soap and laundry detergent need to be 'grey water suitable'.

So what about forever cleaning the filters to keep dripline from blocking up? Every ninth pump out activates an air cleaner which blows air up through the filters and diverts the resulting gunky water to the sewer (self cleaning option). This means that the filters only need to be cleaned once a year. The drippers are one way so shouldn't suck fine particles in and air release valves reduce the risk of this happening as well. Flush points need to be opened once a month to release gunk from the ends of drip lines. Apart from that it's a once a year clean of filters and the pump, which is about as low maintenance as you can get.

Enough of the boring technical stuff, here are a few pics of us installing it.

This is bits and bobs that do the work. When it was filled in and the pipe on the left was cut down to level it looks lots neater. The pipes are (from left to right) reflux valve, secondary filter, primary filter and at the back the main chamber which houses the float valve, pump and air cleaner.

Here is the sub-surface dripline going in.

Then the geotextile goes down. This is to stop lawn roots wrapping around the dripline and to spread the water out evenly.

Here's some dripline in a grid pattern in a fruit tree/globe artichoke bed.

And here's some dripline looped around a fruit tree. This will be covered in mulch soon.

Here's the rotor which directs the water to the different stations. At the moment we have 4 stations on the lawn and 2 on the fruit trees, but we may re-jig this if the lawn does well and we feel that the fruit trees could do with more.

This is one of the filters, I can see tomato seeds from preserving tomatoes today!

It will be interesting to see how much water this saves us. By my reckoning we should harvest around 200-300 litres a day. The great thing about grey water as opposed to rain water is that it's available 365 days a year (as long as you're at home). This means we'll get it when we most need it, through Perth's hot, dry summer, unlike rain water which mainly falls in the cooler 3-4 months of the year. So we should be able to capture at least 70,000 litres of water a year this way, which is the same as our rain water tank harvests. Our lawn should thrive without the need to use drinking quality water on it. The fruit trees should also prosper and become more productive. At the moment we have two stations, the lawn and the trees in the back garden. We'll monitor the results for a while and see if we have enough water to add another station out the front. I'm now considering planting more thirsty trees such as avocado and mango out the front. In a year or so I'll let you know how it has affected our water use.

The other benefits of grey water are more on a community/society level. Perth's water resources are rapidly dwindling and in our rush to increase supply we are putting our security above the well being of future generations. Desalination consumes huge amounts of power which fuels climate change. Current levels of groundwater use is both unsustainable and has unknown effects on ecosystems.Even the delivery of scheme water is very costly, both economically and ecologically. Watercorp, who manage WA's water resources are the number one user of power in the state. This power is needed to clean and pump water to our houses and then pump sewerage away, clean and return it to the ocean. It's crazy that we clean water to drinking quality, only to use most of it to water the garden and flush the dunny! So with grey water we're closing the loop on most of the water in our home and hopefully this will become standard practice in the future.

Think carefully before you install grey water. Ideally you should use a fair bit of water and have enough suitable garden area to put the water on. There's no point paying all that money if you don't use much water and don't have lawn, garden beds and trees to use up the water.

So, what about cost? Our system cost us $4,500 all up.  The council didn't charge us for the permits, but check with yours, some do and some don't. I drew up the plans and filled in the application myself. This, along with ripping up and re-laying the lawn, saved us around $1,000. This is a pretty good price in my view for something with great benefits for our garden and society as a whole. In comparison our rain water system cost us around twice the price. Of course we will never make our money back in lower water bills, water is just too cheap for that now, but that's not the point. Our garden will thrive and we'll be doing our bit for a more sustainable future.


  1. Nice one guys! Thanks for sharing.

  2. Just caught your spot on Gardening Australia, and thought I'd check out your blog as we're setting up to do similar things on a 2.5acre Property based in Wilmot, Tasmania.
    After having just read your article above, which I thoroughly enjoyed, I thought I'd comment and mention that Grey Water also helps stop Aphids from attacking fruit tree's, so there's another benefit for using Grey Water.

  3. Hi Studiojunkyard, Thanks for the info on aphids, I wasn't aware that grey water helps with them. 2.5 acres should keep you busy, good luck with it. And you have rain and real soil over there, so you'll be right. Cheers, Adam

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