Do you know that you are charged twice for the water you use every month -- once to pump it into your house and again to pump it out as sewage?

"The assumption is every gallon of water that you run out of your faucet is going to go back down the drain," says Eric Liskey, deputy editor for garden and outdoor living at Better Homes and Gardens magazine.

But if you use water to irrigate your lawn or garden, that water never makes it into the sewer system.

To save money by making sure you're only paying for the sewer capacity you're using, many utilities offer the option to get a separate meter to measure water usage for irrigation, swimming pools and other outdoor uses, says Liskey. Once installed, the meter will be read every month by your utility company and its reading subtracted from your sewage bill.

The meter will cost you several hundred dollars upfront. But since you'll no longer be charged for sewage capacity you're not using, it should pay for itself within a few years, especially if you use a significant amount of water in the yard.