Whether you own or rent, the faucets in your sink probably came equip with water aerators: the tiny attachments found at the mouth of most faucets. Switching all of your aerators and shower heads to low flow models is the single most effective way to conserve water around the house. You will also save money on your water and heating bills by making the switch. Low flow aerators and shower heads will pay for themselves in a couple of months, and lead to savings down the line.
How to tell if you need one:
Check the numbers printed on the side of the aerators in the bathroom, the kitchen, and anywhere else there is a sink. The rate should be no more then 2.75 gallons per minute or 7.75 liters per minute. If it is any higher, you should replace it with low flow model.
Check your shower heads, the rate on those should be no higher then 2.5 gallons per minute. If no number is printed, put a 2 quart pot in the shower at the center of the water stream, if it takes less then 12 seconds to fill, then you should replace your shower head with lower flow model.
Resources:
http://www.metaefficient.com/bathroom-products/
the-most-efficient-faucet-aerators-of-2008.html
For an up-to-date list of the most efficient water aerators.
http://www.eartheasy.com/live_lowflow_aerators.htm
For more information.
