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Greywater systems - reusing your bath water

Posted by Anna Carlini on 10 August 2017 at 10:45 am

Our water is too clean!

This seems a strange complaint to make, but in the UK drinking water is flushed down the toilet every day, literally! As UK houses tend to only have one water system, all the water that currently flows around our pipes meets drinking standards. It is estimated that on average each person in this country uses 150 litres of potable water a day and a third of a household's water is used to flush the toilet. The amount of water we waste could be slashed by recycling used water in appliances where it doesn’t need to be up to drinking standard.

One way to do this is installing a greywater system. These take water which has been drained from the sinks and showers, sterilises it and runs it back into the house where lower quality water can be used: the toilet, the washing machine and the outside tap, making substantial savings on water bills particularly for big water users like hotels. 

But is this cost efficient on a smaller scale for existing homes?  Unfortunately not if you are looking at a professionally installed system, especially when you consider that the maintenance costs could be in the region of £100 a year.  Better to consider are small-scale options particularly if you are competent at doing DIY. 

For example, models which drain water from just the bath or shower and only use it to flush the toilet. This is a more cost-effective choice, requires little maintenance and is suitable for retrofitting.

Another option is to use your greywater for garden irrigation - particularly if you grow crops in your garden. This would mean draining your bath and shower water into a water butt or directly to the plants through a hose. Just be careful not to use much shampoo or bubble bath! The particles in your bath water won’t harm garden plants, but would be classed as pollutants if they entered a nearby stream or river.

If neither of these options is suitable for your home you can focus instead on wasting less water. You could install water-saving toilets which use only two or four litres to flush and swap in a water-saving shower head. And of course it is also crucial to watch your behaviour around water. Take shorter showers, only put the washing machine and dishwasher on when they are full and don’t leave the tap on when it doesn’t need to be running! These can all help you cut down on wasting litres of wonderfully clean drinking water which at the moment go straight into the sewers below.

Not only are they expensive and difficult to retrofit, but the savings on bills could be made redundant by the maintenance cost which is approximately £100 a year. Therefore the full greywater system is simply not yet an economic choice for homeowners.
 

Image: Eric Norris

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Comments

3 comments - read them below or add one

Barabu

BarabuComment left on: 28 September 2017 at 8:41 am

Yes grey water system in place is a great way to keep water consumption lower! Actually there is this American design called Earthships and I got to know that they use grey water to water plants in the greenhouse or flush toilets (of course using chemicals is thus not allowed if used for the plants).. but still, pretty good idea! This article also explains it well.

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Anna Carlini

Anna Carlini from Comment left on: 4 September 2017 at 9:32 am

Thank you for your pointing this out, it has now been edited. 

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richmc

richmcComment left on: 31 August 2017 at 6:15 pm

"For example, models which drain water from just the bath or shower and only use it to flush the toilet. This is estimated to pay for itself in five years and save 30% of water, which means a 30% saving on water bills."

No it does not!

Even if you are using grey or rain water to flush toilets, the water company will still charge you for sewerage and waste water treatment, if you don't tell the water company you will be in for a hefty bill or fine after legal action when they find out.

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