Using a toilet water-saving device

Last updated Monday 21 July 2008

Save litres of water, and a drop of CO2

Every time you flush the loo, the water you use has to be purified and pumped round again, all of which takes energy. Placing an object in the cistern takes up space, reducing the water needed to fill it. You'll save water without spending a penny.

Putting a device in your toilet cistern that reduces the water used to flush is a quick and easy way to waste less water. Each year it will save twice as much water as you drink. But you may be surprised to hear that it will only reduce your total climate impact by an underwhelming 0.03%.

Although clean water is a vital resource, wasting cold water (as opposed to the hot water in your bath or shower) is not a major cause of climate change: the amount of CO2 emitted to pump, clean and deliver the water that the average Brit flushes down the loo in a year is equal to the emissions from driving just 90 miles.

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Photo: Using a toilet water-saving device

Saves up to 3 kg of CO2 a year

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CO2 reduction 1 out of 5

Cheapness 3 out of 5

Popularity 4 out of 5

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How will it make a difference?

Flushing the loo, like all water use, contributes to greenhouse gas emissions because purifying and transporting mains water requires energy. In fact, the water industry accounted for 1% of the UK's greenhouse gas emissions in 2006.

Popping a water-saving device in the toilet can reduce your flushing emissions by just over a tenth - and more if you buy a larger-than-average device. That said, it's not the most effective way to cut emissions: giving up the household car would save 1000 times more CO2 each year than putting a device in every loo in the average house!

Reducing water waste is a particularly pressing issue in the South East of England where less water is available per person than in Sudan or Syria. In fact, if all Brits (who could) added a one litre displacement device to their cisterns we would save around 70 billion litres of water every year - enough to give an extra 60 litres a day to every household in the South East.

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What's the debate?

Water waste in our homes and gardens is bad - but what about all the water that goes into our food?

According to Waterwise, putting together a typical pub lunch - a pint and a cheese burger - can use up enough water to fill a fish pond.

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How do I do it?

  • Contact your water company for a (typically free) device for each cistern. They are also available in shops for about 2
  • Or make your own from a large margarine tub or water bottle filled with water or sand and sealed
  • Submerge the device in the cistern
  • If it becomes necessary to flush twice, remove the device and replace with a smaller one. If your cistern volume is less than six litres or your toilet was built after 2001 there's generally no need for a device
  • Get a water meter to gain maximum financial benefit
  • Consider installing a low-power shower
  • For the really dedicated, consider setting up a composting loo

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What's stopping me?

Pub Fact

  • A third of your daily water usage (around 50 litres) goes down the toilet
  • The average person flushes the home toilet five times a day
  • Around 0.7 grams of CO2 are involved in delivering one litre of clean mains water to your tap and treating it after use
  • A single toilet flush can use as much water as the average person in the developing world uses every day for drinking, washing and cooking
  • The average toilet uses about eight litres per flush, although this varies with age. Pre-1991 cisterns can flush more than ten litres down the drain
  • Office workers in the UK flush a total of about 200,000 times per minute during the working day
  • To produce 3000 calories of food a day for each of the world's 6.7 billion people, we annually use enough water to fill a canal one kilometre wide, as deep as Big Ben is tall, and long enough to circle the Earth twice
  • If present levels of consumption continue, 66% of the world population will inhabit "areas of water stress" by 2025
  • We use 70% more water today than we did 40 years ago

"I have a modern, state-of-the-art toilet. Have I really got to start filling the cistern with 'displacement devices'?"

Toilets designed since 2001 are more water-efficient, and cisterns with a volume of less than six litres often don't need devices to reduce their flush volume. In this case, adding a "cistern displacement device" can hinder flushing and even make the cistern overflow. Best to check first, or keep a pair of wellies in the bathroom.

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Anonymous 2009-02-11

I put old jam jars filled with water in the cistern.

CAP67, Liverpool 2009-02-07

This was so quick and easy. I should have done it along time ago!

Baz, Shropshire 2009-02-05

hello bloomers,
Reading the comments below, most of you have twigged that the water companies use the meter to charge for waste disposal, so less in, less out and money saved. For meter users only, if you want to save some more, look at your water bill, have you been charged for the removal of the rainwater from your roof and hard standing? If the answer is YES check to see where this water goes, ensure the rainwater goes to a soakaway not the storm or foul drain, even better collect it in an underground tank and use it to flush the toilet and other uses such as a shower or laundry. When your rainwater is not disposed of by the water company, make sure they know this and are not charging you for a service not provided, and insist that this is properly backdated to the time when you started to get rid of your own rainwater, not just last April as they will want to.

Anonymous, Tunbridge wells 2009-02-05

We, too, use grey water for flushing the toilet. In fact our motto is, "Bucket, don't flush it!" The kids think its fun. We are metered and our sewage bill has gone down 5 a month, so somethings working.

anon, glos 2009-01-28

When we've had a shower or bath I reuse the water in the toilet, I take the cistern lid off and bail a bucket full of used(grey) water to refill. This saves me water and money! If like me you are on a water metre then you will be charged for clean water coming into the house and used water leaving the house. Since my son left home my monthly water bill has gone from 33 to 19 for a family of 4 clean people with an auto washing machine.

Anonymous, Dublin 2008-09-01

It's easy, free, needs no professional installation and it doesn't interfere on how the flush works. Brilliant solution!

Spuitelf, The Netherlands 2008-08-29

Another possibility is changing the reservoir to one with a double option button: small button for small productions (urine) and a larger button for larger productions (faeces). Saves a lot of water!

Anonymous 2008-08-28

Got one free from the water company. Lifted the lid off the cistern and put it in there. Good for the world and it saves us money on our water bill too!

Ironrock, Hemel Hempstead 2008-08-16

Simplicity at its best.
At zero cost, and immediate infinate benefit who wouldn't do this?

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Glossary terms used on this page
CO2, or carbon dioxide, is made up of the elements carbon and oxygen. It exists quite naturally in our atmosphere, as part of the carbon cycle. Everyday processes in the plant and animal world both add CO2 to the atmosphere and take it out. However, because it is a greenhouse gas - meaning it affects the temperature of the earth - the exact level of CO2 is important. Burning fossil fuels releases CO2 into the atmosphere, hence the anxiety that extensive use of these fuels is causing climate change.
Greenhouse gases
Greenhouse gases raise the earth's temperature through the greenhouse effect. There are six main examples. As well as carbon dioxide, they include: water vapour, methane, nitrous oxide, ozone and CFCs (which include sulphur hexafluoride, HFCs, and PFCs). Of these, carbon dioxide, methane, nitrous oxide, sulphur hexafluoride, HFCs, and PFCs are controlled under the Kyoto Protocol to limit their concentration in the atmosphere. The heat warming capacity of each gas is measured by its 'global warming potential': how much heat it traps depends on its chemical make-up and how long it stays in the atmosphere.
Water meter
A device used to measure the volume of water used by a household or business. Billing people for the water they actually use, rather than a fixed annual charge, is increasingly common in the UK, and is regarded as an incentive to users to avoid wasting water. navigation


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