Rainwater Harvesting at Dave's House
This is a short description of my system at home. It provides water for one inside loo and irrigation around a conservatory and the garden, primarily for the hops used for my home brewing. It allows us to go away for a few weeks/months in the summer and the irrigation runs automatically using the available rainwater but can top up with a small amount of mains water if needed. There are 8 water butts (220 litres each), 2 small water butt pumps, 2 timers, garden hose and some valves.
Part 1 – Supplying the Loo.
This has 4 water butts, 3 are sat on a layer of bricks and the 4th on a wooden stand about 1.3m high. A rainwater diverter in the downpipe feeds into the 1st butt which overflows into the 2nd one. This 1st butt acts as a knock-out for big bits of debris in the rainwater and is used to fill watering cans. The 2nd and 3rd butts are connected by a length of garden hose attached to their outlet taps (which are left open all the time) so these two act as a single 440 litre tank. When the 4th butt (on the platform) is empty an electric water pump in the 3rd butt is turned on (electrical outside socket) to fill it. Just before doing this I put a squirt of bleach into the butt which prevents the loo from turning black – not nice. A length of plastic pipe takes the rainwater by gravity from the top butt outlet tap, through the wall and a connection into the mains water pipe supply, to the loo. Two manual valves are installed so that either the rainwater or the mains water can be selected to go to the loo (just have to close one and open the other and visa versa) – see diagram. There is an overflow to drain from the 2nd butt for when there is a bit too much rain and everything is full.
Part 2 – Irrigation System
This also has 4 water butts which are all mounted on a wooden platform about 1.3m high. They are all connected together by garden hose from their outlet taps so act as a single tank. A rainwater diverter in a downpipe feeds into the end butt. An electric pump in the 2nd butt is activated from a socket in the conservatory. This includes a plug-in 24hr programmable timer which can turn it on for a set time in the morning and a set time in the evening (or whatever is required). The pump outlet is connected to normal irrigation pipe with those little screw-in sprinkler heads which goes around the garden. A T-piece in this pipe takes another pipe into the conservatory which has adjustable screw-in nozzles, most of which are set to very low flowrate.
A length of garden hose from a T-piece in the connecting hose after the 4th butt drops down to another T-piece, one of which goes to a tap for filling a watering can and the other through the wall into the conservatory and a garden hose gun.
Part 3 – Interconnection
During periods of low rainfall the Loo system can run out of rainwater. There is a length of garden hose from a T-piece in the Irrigation system tap outlets to the Loo butts. This has a small valve in it which allows the Loo butts to be topped up manually.
When we go away for long periods in the summer it is probable that the Irrigation system will run out of rainwater. Before we go I connect the garden hose mentioned above to an outside mains water tap with a battery powered programmable timer and leave the tap in the open position. The other end of the hose is diverted into the end butt of the Irrigation system. The timer then allows mains water into the irrigation system for about 5 minutes every day. This is sufficient to allow the level in the butts to rise high enough for the irrigation pump to run every few days – until it rains again an the butts fill up. Not perfect but better than nothing.
