3 A toilet with an old cistern can use around 9 litres of water every time you flush. You can install several devices which reduce the amount of water that it flushes.
A Hippo water saver for cisterns with a 9 litre flush or greater is a very simple to install bag system which reduces the flush by up to 3 litres. Checkout their web site which shows full fitting instructions at www.hippo-the-watersaver.co.uk/http
NB Most water companies will supply them free. Contact your local water board to ask or visit their web sites which also have more water saving ideas.
A Save-a-flush bag is a similar system for cisterns with a 7 litre or greater flush which is a bag you simply drop into the cistern, hold it a moment, then it expands to reduce the flush by about 1 litre. http://www.save-a-flush.co.uk
Most water companies will supply them free to. Contact your local water board to ask, or visit their web sites for more water saving ideas