Grey Water System – Half Barrel Box Trough

We aren’t going to have a septic tank at the house, instead we are going to have a composting toilet and a grey water system.

What is Grey Water?

Grey water is everything that doesn’t come from the toilets, i.e bathroom sinks, shower drains etc.  The kitchen is considered by some to be black water as it contains lots of fat from cooking and bits of food.  The general consensus on the kitchen sink is that its not worth the hassle of trying to build a fat trap and filter to remove food particles, which has to be cleaned out periodically (and is absolutely disgusting from what I hear) and so should just be treated like black water.

Half Barrel Box Trough

As we don’t have a septic tank the solution I found was a half barrel box trough.  A half barrel box trough is made out of half of a 200 litre plastic drum buried underground.  This creates an air cavity where the water can take its time to sink in and where colonies of bacteria will grow to eat any organic matter and fat from food.  This is great because it won’t smell and you don’t have to deal with the fat. If you plant trees and other plants around it they can still get the benefit of the extra water without it being a health hazard for humans or a bad smelling area.  Commercial equivalents of this system are called infiltration galleys.

The Problem with Black Water

In common houses the grey water gets mixed with the black water which immediately turns it into black water.  Grey water is relatively clean and can be used (with some precautions) to water plants around the house without any sort of treatment, creating what is known as “the oasis zone”.  The combining of grey water with black water means that the water treatment plants have to deal with a lot more water than is necessary which ends up turning into pollution.

If all of our houses had grey water systems we would have lusher gardens, lower water bills and would drastically decrease the amount of black water that needs to be treated also reducing the problems that are associated with dumping “treated” water into the sea.

The Oasis Zone
Re using our house hold grey water is a great solution to this problem and easy to implement if you are building a house from scratch.  If designed properly, the use of this “waste” stream can be used to create a beautiful,  lush area of vegetation around the house that doesn’t need any extra watering.

Here is a video on how we made our grey water box trough:

If you’re interested in learning more about grey water systems check out:

and check out their great book:
Create an Oasis with Grey Water

I will also be doing more posts about our grey water system and composting toilets in the not so distant future.