A faucet aerator is a little device at the end of a faucet that adds air, and thereby provides a uniform flow while also restricting flow. Aerators will come with different gallons per minute (GPM) flow rates that are usually stamped on the side of the aerator. Over the years, the maximum flow rates have been reduced in an effort to conserve water, so many fixtures could be upgraded with newer aerators to conserve water.
The current California Plumbing Code requires kitchen faucets to have a maximum flow rate of 1.8 GPM. Bathroom faucets (known as “lavatory” faucets in code language) are required to be a maximum of 1.5 GPM. The California Green Building Code has set a voluntary standard of 1.5 GPM for kitchen faucets, and while this is currently voluntary, look for this to be the new standard in the coming years.
Generally speaking, the lower the flow rate, the more water will be saved. So take a look at your faucet aerators and determine their flow rate, and see if this could be an opportunity to save water. Just unscrew the aerator, bring it to your local plumbing store to find a lower flow aerator, and screw the new aerator in.