How to Repair a Dripping Single-Handled Faucet

For too long now, a stubborn drip-drip-drip has been descending from the one-handled kitchen faucet in the home of Richard Trethewey, This Old House’s plumbing and heating consultant. “Most people will ignore a dripping faucet out of fear or ignorance,” says Richard. If they deal with it at all, it’s usually by cranking the handle so hard they risk tearing a rubber washer or cracking something and making the leak worse. At his own Second Empire house, it’s more the case of the cobbler’s child whose feet go unshod.

When Richard does finally find a free morning to break out the wrenches, he stems the tide within 15 minutes. A homeowner with a little wherewithal should be able to finish similarly simple repairs in half an hour. “Fixing a faucet drip won’t solve the world’s water woes,” says Richard. “But it will save the finish on your enamel sink and end your Chinese water torture.”

Step 1: Single-Handle Cartridge Faucet Diagram

A single-handled cartridge faucet is easy to disassemble. Just pry off the decorative cap on the handle, remove the handle screw, tilt the handle back and pull it off. If there’s a threaded retaining clip holding the cartridge in place, use needle-nose pliers to remove it, and then pull the cartridge straight up. In Richard’s case, only the cartridge needed replacing. If the O-rings are cracked, remove the spout and cut off the old O-rings using a utility knife. After coating the new O-rings with nontoxic, heat-proof plumber’s grease, reassemble the unit.

Pro Tip: Richard Trethewey, This Old House plumbing and heating expert, advises: “Look at the faucet and try to understand how it was put together, then go in reverse.” He uses a pocket knife to pry off the decorative plastic cap, then gently wiggles the handle back and forth to loosen it before sliding it off.

When pulling the cartridge, grip the stem with pliers and pull up firmly, sliding the unit straight out without any side-to-side twists. If the leak was coming from the base of the handle rather than the spout, that indicates the O-rings need replacing rather than the cartridge itself. When installing a new cartridge, make sure it goes in the same position as the one you removed, so the holes that deliver hot and cold water to the spout won’t be mixed up. Fit the retainer clip snugly into its slot before reassembling the bonnet and handle.

Step 2: Prep the faucet for repair

The first task in any faucet repair is to shut off the water feed by closing the valves under the sink; if there are none, Richard shuts the water main. He turns on the faucet to bleed the pipes of water, then plugs the sink’s drain with a rag. “The smaller the part,” says Richard, “the more it wants to take a dive down the drain.”

Pro Tip: Richard Trethewey, This Old House plumbing and heating expert, advises checking that your shutoff valves actually work: “Test the faucet. If the water still comes on, your valves aren’t working and you will need to shut off the water at the next valve down the line or at the water main.”

Step 3: Remove the handle

To figure out the next step, “look at the faucet and try to understand how it was put together, then go in reverse,” advises Richard. This single-handled kitchen faucet has a cartridge under the handle. The cartridge has holes that mix the hot and cold water to deliver different temperatures depending on how the handle is turned. If it’s worn or cracked, water will seep through to the spout. To remove and replace it, Richard first uncovers it by using a pocket knife to pry off the decorative plastic cap—similar to those on two-handled “hot’ and “cold” units—to expose the screw that holds the handle in place. Richard removes the screw; then he gently wiggles the handle back and forth to loosen it and slides it off.

Step 4: Remove the bonnet

The faucet handle isn’t the only thing between Richard and the cartridge; he must unscrew the bonnet——being careful not to scratch this chrome cover for the cartridge assembly—with a pair of slip-joint pliers. Then he uses needle nosed pliers to grab the U-shaped retainer clip, which slides through the faucet base and around the cartridge to secure it in place. As he takes out the pieces, he carefully lines them up to the side so he’s sure not to lose anything or mix up the order of the parts when it’s time to reassemble the faucet.

Step 5: Install new cartridge

Richard grips the stem of the exposed cartridge with his pliers. To overcome the suction resistance of the rubber O-rings at the top of the cartridge, he pulls up firmly, sliding the unit straight out without any side-to-side twists. Had the leak been coming from the base of the handle, Richard would have known that the O-rings needed replacing. But since this is a case of a dripping spout, he’s already surmised that the cartridge is the problem. He installs a new one, making sure that he places it in the same position as the one he just pulled out, so the holes in its side that deliver the hot and cold water to the spout will not be mixed up. He then fits the retainer clip snugly into its slot and reassembles the bonnet and handle. With this process, Richard is able to fix his water woes without having to replace the old faucet entirely.