Stop Wasting Water - Set up a Simple Passive Grey Water System

This post was most recently updated on November 5th, 2020

If you are looking for a simple, but effective grey water system for your garden, I explain below what we have done with ours.

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We are on a tank water supply. So the rumor that it was going to be a hot dry Summer sent chills up my spine. This is our first year with a tunnel house and we are attempting to grow 100 tomato plants, plus other things that need plenty of water.

We cannot afford to be wasting our water on plants, but I was very aware of the amount of water we were putting through the washing machine with all the household laundry we were doing.

I figured if we could capture the grey water and send it to the plants, it would solve both the issue of flooding out our sewerage field with too much water, as well as providing the plants plenty to drink.

Setting up the grey water system was surprisingly easy and very cheap to do. This is a simple, passive grey water system, we have no tap ware for it inside, but we did install a faucet on the outside barrel which has been helpful.

The hardest part was working out where to put the hole so we didn’t hit the timber in the walls, while still being high enough to miss the taps on the inside. We tested the hole with a small drill before using the hole saw.

We have used:

32mm pipe with 2 90 degree elbows, one for each end.
Clear silicone
Bulkhead Fitting
Screw in faucet
Poly hose
Hose fittings
Soaker Hose

We secured the pipe to the wall with a pipe clamp. Then I simply pushed in the washing machine outlet hose into the grey water system out flow pipe. Make sure it is well tucked in so it doesn’t ping back out. Ask me how I know…

For the outside part of the grey water system we have used a plastic 55 gallon plastic drum that we got from a place in town that has them as scrap.

We built a small stand to raise the water barrel off the ground to add the gravity pull to help with passive emptying. Even though we live on a hill, the area that the vegetable garden is on is almost level with the path around the house.

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As we wanted the grey water system to drain passively, we had to add some extra height to the barrel. We get very high winds here, so I used some roof strapping to anchor the barrel to our wall.

I drilled a hole in the bottom of the barrel and put a long string with a heavy nut tied to it in the top hole. By tipping the barrel I could pull out the string through the lower hole.

This gave me a line to thread the hose attachment on the inside of the barrel down, then I could pull it through the hole and screw the outside piece on.

Once the bulkhead was attached we could wiggle the barrel in under the elbow and check it’s position before sealing around the pipe hole on the house wall with a good glob of clear silicone.

I also sealed around the bulkhead where it comes out of the barrel.

Then I used a long length of black poly hose to take the water out to the tunnel house. At the tunnel house we have a soaker hose already laid under the mulch layer. I simply plugged the two hoses together and Bob is your Uncle.

In theory.

We had a problem.

There is just not enough pressure in this passive grey water system for a slow-leak soaker hose to be able to keep up with the amount of water from all my laundry!

So I resorted to drilling some very small holes in the hose at the base of each plant. This has worked wonderfully. It takes about 2 hours for the whole grey water drum to passively empty to the roots of my greenhouse plants.

You do have to be careful what you put in your laundry if it is going on your plants. We use our own homemade laundry soap.

UPDATE 2020

I have had issues with the fibres from the washing machine clogging up the soaker hose, and the tank draining too slowly, so I have added a sump pump to the tank and some drip tape to the tunnel house – check it out in the video below.

Items I used (not necessarily the brand, but you can see what sorts of things you need)

1/2 inch Poly hose – us kiwis call it 13mm irrigation hose

Drip tape (16mm)

Joiners/connector to tape from poly hose

T joiners

Ends for the tape

Pump

3/4 inch to 1/2 inch hose converter

1/2 inch hose connector

I got all my stuff from Bunnings and https://www.irrigationexpress.co.nz/