Water Capture

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The main form of water capture involves collecting rainwater from the gutters, storing it in a tank and using it to flush toilets, fill the washing machine and water the garden.  The second form is to reuse bath and shower water (‘grey water’) to water the garden. The definition of grey water also includes water from the kitchen sink, but this tends to be a bit too mucky to be worthwhile.

Rainwater harvesting systems start with the humble water butt sat below a gutter down pipe and used for watering the garden. However, as soon as you start looking at flushing loos and washing clothes the cost and complication escalates rapidly. The rainwater is still taken from the gutter down pipes, but needs to be diverted into a large tank via filters to remove debris. The tank is often put underground due to the large size, which can be expensive, with the waste from the debris filter and overflow plumbed into the original drainage system (often the foul sewer). There then needs to be a good system of plumbing installed in the house to take the rainwater from the tank to the loos, washing machine, external taps etc. The water has to be pumped through this plumbing to get to the point of use, so that needs electrical connection, sensors, control units etc. There also needs to be a connection to the mains water to top up the tank during dry spells, otherwise you would have to become seriously anally-retentive during heat waves.

The cost of a rainwater harvesting system for domestic use will depend largely on the installation. The underground varieties are probably only sensible to put in during construction work. The above ground varieties will be more sensible for existing houses, but the plumbing will still cost a bit. A system that can store 2000 litres of rainwater is likely to cost at least £2000 installed. A simple water butt for watering the garden, on the other hand, is likely to cost from around £12.

Water and sewerage charges for a typical household are around £350 a year and both are based on the amount of water used. A full harvesting system can drastically reduce the amount of mains water you get through, so can seriously reduce the bills. Payback time is likely to be between 5 and 20 years, depending mainly on when and how the system is installed. Future price rises from the utility companies will reduce this.

If you want to learn more about rainwater harvesting systems, Rain Harvesting Systems can help, but Rain Water Harvesting are excellent and may be a better first port of call.

Grey water from baths and showers is good for using on the garden. The low concentration of detergents, salts and general filth means it won’t cause problems, especially if you use the more eco-friendly bath products. There are many ways of capturing grey water for reuse, but it is generally not a good idea to store it for too long as it can get smelly. The two main products on the market are an in-line diverter and manual pump with hosepipe. The former is a box that clips into the waste water pipe (before it joins the toilet soil pipe) and is very simple, having a manual pull cord arrangement to direct the water to sewer or divert it into a hosepipe. The latter is simply a hosepipe with an inline, manual action bladder pump.

The simple diverter costs around £30 and are available from Water Two. The hosepipe siphons cost about £20 but need to be hung out the window during use and stowed away somewhere between uses – see the shop to get one.

What to do

There is an expression involving horses and courses that is appropriate here, so go for whatever seems best for you.

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