siphon diagram

Action: Siphon your summer bath into your garden water butt

A bath typically contains 100 litres of water, so in summer or times of drought, reusing it for your garden makes sense.

This action might sound slightly out of left-field, but if you think about it, it really is a good idea. It’s a simple way to save hundreds of litres of water, save money, and help your own garden in times of water shortage.

Simply use a hosepipe as a siphon from your bath to the garden water butt, or of course directly onto dry areas if they need it at that time. It’s a no-brainer!

What to do


A siphon is very easy … it’s just a filled hosepipe that takes advantage of gravity to drain liquid from one level to a lower level, in this case from your bathroom to your garden (which is usually lower!).

To start the siphon, you have to fill the hose with water. You can do this from the cold bath tap, quickly plunging the end of the hose under the bathwater once it is full. Water will flow for as long as you keep the end of the pipe under the water. Don’t let any air get in or you will have to start again; see the diagram below.

You can also buy siphon pumps to start the water flowing, but the tap method should work OK!

The other end of the hose needs to be below the level of the bath, and you can put the end directly into your water butt to use later, or allow the water to sprinkle directly on to the garden where water is needed. It doesn’t matter how long the hose is, but you’ll need to uncoil it to make sure there are no kinks or air in it, and a very long hose might mean water will flow more slowly.

Did you know? … water that is re-used in this way is called grey water.

If we assume a family of four in the house have a bath once a week, you will be saving 400 litres of water every week, which is over one and a half tons each month!

You can see how a siphon works in this simple diagram:

siphon diagram
(click for a larger image)

Why is this important?

Water is a precious life-giving resource and we need to treat it as such, and not take it for granted. Our water supply systems take supplies from our natural environment and the disposal systems often pollute, so if we can reduce the use of water there is less strain on the ecosystem and our infrastructure.

Even in countries where a continual supply of clean water is taken for granted, systems are under strain. Not just our infrastructure, but supplies too; aquifers and reservoirs get very low each summer and our water tables (the natural level of underground water) are being reduced. This impacts on our eco-systems to the detriment of plants and wildlife, as well as on our own water security.

There are many advantages to taking this action:

  • it saves water, a resource we take too much for granted in the developed world
  • it saves money if you pay by the cubic metre, as most of us do in Europe
  • it reduces the chance of water shortages during droughts in the summer months
  • less strain on the water system means safer, cleaner, healthier water for us all
  • you are reducing the use of fluoride and other chemicals used to treat water

Just one thing to be careful of … due to it containing soaps and shampoos, it’s best not to use bathwater on food crops. It is fine to use bathwater on lawns, shrubs, and flowers though.

Take action

Think about this and other methods of re-using water in your garden, especially during the hot summer months. Also, take a look at our earlier article about rainwater harvesting and garden water butts.

Please sign up for our fortnightly bulletin ‘Take Action’ using the form below, and give us a mention on your social media. Thank you for your support.

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