A SIMPLE DIY TOILET
Flushing your existing downstairs toilet with rainwater can save you money and is a useful adaptation if you haven’t the space to install an outdoor compost toilet. Klaus Muecher Erskine shows you how.
Article first published in 'Permaculture Magazine' No. 51
Here is a simple design to feed your downstairs toilet with rainwater collected from the roof. Anyone with intermediate DIY and plumbing skills can do this and have a feeling of satisfaction at every flush!
To build your own rainwater toilet you need:
Ideally you will have a down pipe near the outside of your downstairs bathroom, where the water butt can be placed. Because the level of the water butt needs to be higher than the toilet it is necessary to build a sturdy pedestal (190 litres = 190kg / 42 gallons = 420lbs!) outside.
I used four lengths of 50 x 50mm (2 x 2in) leftover building timber and some 25 x 100mm (1 x 4in) for the water butt to sit on. This structure needs to be bolted to the wall with proper wall fixings, such as M6 or M8 rawl bolts (do not use ordinary wall plugs).
A hole is drilled through the wall, so the 15mm (in) pipe can go through to come out above the cistern (better to drill the hole from the inside). To connect the water butt to the 15mm pipe I used a brass connector with an adaptor (22 to 15mm / to in) and a flexible stainless steel washing machine hose. Make sure that the rubber foam O-ring that comes with the water butt is fitted, otherwise the water butt will leak!
It might also be a good idea to be able to turn off the supply from the water butt when you want to carry out maintenance. At the moment I just wait for the days when the water level is low or empty. Otherwise I empty the water butt into another one situated beneath.
Making A Dual Feed
Most modern toilets are fed from the bottom but the water butt is unlikely to provide enough pressure for that, so a side-feed valve is better, if not the only option. The pipe that usually feeds the toilet with mains water (and is probably located behind the toilet somewhere low) is cut and a washing machine tap installed. With this tap you can switch from mains to rainwater. Using two separate valves in the cistern ensures that no mains water is mixed with rainwater, which is a requirement to prevent any contamination of your drinking water.
To install the additional float valve a second hole has to be drilled into the side wall of the cistern. If your cistern is ceramic then prepare for an afternoon of careful drilling (it took me ages!). If plastic, you should be through in a swoosh! A 22mm (in) instead of a 15mm (in) valve is probably going to work better, but I wanted to use what was in the garage where possible. The pressure is not fantastic as the level in the water butt goes down with every flush and sometimes it takes a little while for the cistern to refill. In our house with three boys the toilet does tend to work overtime at times! Still, when we get lots of rain we can run the toilet entirely on rainwater – brilliant.
Most people who see the system for the first time assume that rainwater is going to stain the toilet green, or make it filthy in some way. So far though there has not been any staining, and the conversion has been used for several months. The outlet of the water butt is about 75mm (3in) above the bottom, so most particles should settle at the bottom. The side feed valve usually has a filter. I have taken that out to have maximum water flow. Obviously every house is different and this design is very crude.
If you decide to have a go you will have to experiment a little bit with your conversion. The overall cost of this project was about £25, but I had building timber, some left-over pipe and a water butt. If you had to buy everything then the overall costs should not exceed £100. It’s been a great project!
Just one other thing: When it gets cold outside the copper pipe convects some of the cold into the bathroom and a cold pipe unfortunately attracts the humidity in the air. This means that on cold days there can be a little condensation on the pipe. We just wipe the pipe with a cloth, but if the pipe was insulated the problem would not occur.
Alternatively the pipe could be boxed in along with insulation. In colder areas of the UK I would build the water butt into a wooden, insulated cabinet outside to avoid the water freezing. On the other hand, have you noticed just how much warmer the winters are these days...?
I could have designed the system so that it switches from mains to rainwater automatically, but I wanted to come up with something that was cheap, simple and easily made. If there are people out there with more experience in plumbing, I would appreciate their feedback and ideas. Please get in touch via PM [email protected]
Klaus is a lecturer and trainer in engineering. He became interested in permaculture three years ago after purchasing 0.45 hectare (1.12 acres) of pasture which he and his partner Sarah are converting to an organic heritage orchard, a woodland and a hedgerow project to support wildlife habitat, using local varieties.
The fully illustrated version of this article appears in PM51 and can be purchased now as a back issue.