Rainwater & greywater harvesting

by James Lea, 14 May 2007

Introduction

Every year many tons of rainwater fall on our homes. For most of us, it simply goes down the sewer, and once out of sight, it's out of mind. Simultaneously, we generate vast quantites of greywater from our baths, showers and kitchen sinks. Again, it is common to regard this as 'waste', to be got rid of quickly, somewhere far away.

Both these approaches are anathema to permaculture, an ecological design system which seeks to minimise the impact we and the environment have on one other. One key technique permaculturists apply is to establish beneficial relationships between systems: this often means coupling them together, so that the 'waste' from one system becomes an input to the next.

This article explores these concepts, and shows how we are reducing our waste water outputs, instead turning them into useful inputs for our gardening and growing biomass crops. It follows the SADIM permaculture method - Survey, Analysis, Design, Implementation and Maintenance.

Background

We've recently moved into a 1930s semi-detached house, having lived in a Victorian terraced house. This presents us with many opportunities to eco-renovate, including:

1. Fitting cavity wall insulation, and thermafleece insulation to the roof space;
2. Installing a modern energy efficient heating system, powered by gas condensing boiler, wood burning stove with a backboiler, and solar panels;
3. Growing perhaps 50% of our own food supply, minimising food miles
4. Growing fast growing biomass crops such as willow to supplement the wood we buy in to fuel our wood burning stove;
5. Harvesting rainwater and greywater to provide a water supply for our crops, even in times of drought.

This article focuses on the last point - harvesting rainwater and greywater.

Rainwater and greywater harvesting

[key component - Wisy filter]

[photos of Wisy filter]

[rainpipe diagram]

[intercept points for rain and greywater]

[Installing Wisy filter]

[Some comments on the filter]

[Installing connections to water butt & discharge tank]

[Rainwater into water butt]

[Photo]

[Greywater into discharge tank, then garden - tank is for buffering]

[Photo of green tank]

[Photo of drain line]

System Performance

Very good initially, but filters need to be kept clean (esp. greywater)

Volume of water collected

Next Steps

Greater storage capacity

larger diameter (3/4") drainline

-- (c) James Lea, www.GreenLiving.co.uk, 2005 - 2007 --