Practical notes on how to save water on...

Friday, 12 November 2010


Hello again!

I wanted to talk about the WATER TWO and dispell a few myths about drainage and what happens when water goes down the plug hole. All water from the kitchen sink, the bath, a wash hand basin, the shower, goes down a pipe into the sewer. All drainage or waste pipes should have a U bend where water collects, to stop bad smells rising up the tube and filling the house, but beyond the U bend or "trap" the tube will be empty, most of the time. If you were able to look inside a drainage tube around your house, it would probably be empty -it is not full of dirty water all the time like the sewer underground -it is usually empty until someone.... lets the plug out the bath, or the sink, or runs the washing machine.

If you go to a hardware store you can buy straight lengths of drainage tube and bends but not valves as normally there is no need to have a valve.... however, if you are keen to save water a valve is very useful to divert greywater to recycle it for other uses like watering your plants.

A company in the UK sells drainage water valves called WATER TWO -this neat device lets you divert water from your bath for use in the garden. You attach it to the down pipe directly from the bath -this relatively clean water can be recycled to be used in the garden. When you take a bath leave the plug in. Go outside turn the WATER TWO valve to divert, then pull the plug out the bath and open the spray on your garden hose to start watering all those thirsty flowers.

This is one of the pathways identified in my previous post on the water use hierarchy. This is a great way to water your garden at no extra cost and you can fit it without getting wet! This also lengthens the pathway of the water between water treatment cycles as water will naturally be filtered by the plants before ending up in the atmosphere or travelling to the nearest river or water course. This means by the time the water  reaches a water treatment plant (via a river or lake) to be converted into drinking water, it is already quite clean.

A bath uses up to 80 litres of water and if you have a shower over the bath, using shower to collect water, this might collect 40 litres of water. Bathing uses roughly 30% of all household water and provides a regular and reliable source of water for your garden, unlike rain!

If you are keen to start using a WATER TWO diverting valve then you must use it responsibly, remember that bathwater is not as clean as water direct from the tap:

Don't store this water in a barrel. Over time, e.g 1 or 2 days or more, microorganisms like bacteria will multiply and you want to avoid this as you will come into contact with this bacteria as you water your garden.

Don't spray plants directly, water the soil.

Don't water plants that you are going to eat, e.g. lettuces.

Do use environmentally friendly soap. Products with low salt (Sodium Chloride), Boron and Phosphates are better. Avoid using bathwater that contains bleach or other household cleaning products, these chemicals will not be good for your garden.

Don't use the WATER TWO system if someone in your household has an infectious disease or diarrhoea, because watering your garden could increase the risk of other people becoming ill.

Greywater tends to be a bit alkaline, so flowers like Azaleas which prefer acid conditions don't grow well with this type of watering. Clay soils have low permeability so can't absorb water easily and may not cope with absorbing the salt found in greywater.  Keep an eye on your plants, if they look weakened by greywater, alternate use with normal watering from the tap and water different parts of your garden to spread out the exposure to greywater.

Once you have watered your garden, remember to wash your hands before you eat!