One drip per second from a leaky faucet equals 3,000 to 8,000 gallons of wasted water a year, according to Paul Patton from Delta Faucet and Chuck White from the Plumbing-Heating-Cooling Contractors Association. Here are tips from White and Patton about how to fix the leak:

• Turn off the water. Plug the sink so you don’t lose parts down the drain.

• Identify the brand and model of the faucet so you buy the right parts. Most of the market was washer-and-seat 30 years ago, said Patton. Now, many manufacturers have eliminated those two parts for what’s known as a cartridge.

• Remove the faucet handle with a screwdriver or Allen wrench.

• On a single-handle faucet, you’ll now see a metal ring; tighten it with needle-nose pliers. If this doesn’t fix the leak, forge on. Because single-handle faucets vary by brand, it’s best to follow instructions that come with the parts.

• For a two-handle faucet, you’ll see a nut. Remove it. Pull the stem straight out, and with it comes the cartridge. If it’s an older seat-and-washer gizmo, just turn the stem open to lift out the stem and washer. Look down into the hole (you may need a flashlight) to see the seat. If it’s shiny and smooth, it’s OK; if it’s not, it’s the source of your troubles. Unscrew it with the seat-removing tool.

• Replace old parts with either a new cartridge or new, identical seat. Replace the washer too.

• Reinstall the parts in reverse order.

Degree of difficulty: Tricky enough to show why plumbers were invented.

Tools required: Screwdriver, needle-nose pliers, adjustable wrench, Allen wrench. And depending on your replacement part, the correct “seat removing tool” (with a hexagon fitting, or a square protruding from the end).