Why does my kitchen faucet leak only when the handle is turned on?

A leak that occurs only when the water is running usually points to a loose packing nut, a worn O-ring around the valve stem, or a cracked supply line. The water pressure pushes through a gap that is sealed when the faucet is off. Check the handle base and under-sink connections for moisture while the water is running.

Can I fix a leak without replacing the whole faucet?

In most cases, yes. The leak is usually caused by a worn cartridge, O-ring, washer, or supply line. These are replaceable parts. You need to identify the faucet brand and model to get the correct replacement. If the faucet body itself is cracked, which is rare, then a full replacement is necessary.

How do I know which cartridge to buy for my faucet?

Look for the brand name and model number stamped on the faucet body, usually on the base plate or under the handle. Check the manufacturer's website or a plumbing parts store with the model number. If you cannot find the model, remove the cartridge and take it to a hardware store for matching, or contact the manufacturer's support.

Is a dripping faucet just a waste of water?

Yes, a single drip per second can waste more than 3,000 gallons per year, according to the U.S. Environmental Protection Agency. Beyond the water waste, a leak can also cause mineral buildup, corrode the faucet, and damage your sink or cabinet. Fixing a leak promptly saves water and prevents more costly repairs.

Kitchen Faucet Leak Diagnosis: Find the Source Before You Repair

Is the Leak at the Spout or the Base?

The first question to answer is where the water appears. A leak from the end of the spout, even when the faucet is off, usually points to a worn cartridge or valve seat. A leak pooling around the base of the faucet, on the counter or sink deck, often comes from a failed O-ring or a loose mounting nut.

Run the faucet for a few seconds, then turn it off. Dry the spout and the area around the base with a towel. Watch for the next few minutes. Water that continues to drip from the spout indicates a cartridge problem. Water that seeps out from under the handle or around the base, especially while the faucet is running, suggests a seal or connection issue.

Do not assume one leak has a single cause. A faucet can leak from the spout and the base at the same time. Identifying the exact location now saves you from buying the wrong replacement parts later.

Close-up of a kitchen faucet with water dripping from the spout and a puddle at the base

Check the Handle Area for Cartridge or Stem Leaks

If water seeps from around the handle, either when the faucet is on or off, the leak is likely inside the valve body. A worn cartridge, a loose retaining nut, or a deteriorated O-ring on the valve stem can allow water to travel upward and escape around the handle.

First, tighten the handle screw or set screw if it feels loose. Then wipe the handle dry and run the water. If the leak persists, the cartridge or stem seal is the culprit. Replacing the cartridge is the common fix, but you need to know the faucet brand and model to get the correct part. Look for a brand name on the handle or base plate.

For a single-handle faucet, the cartridge is usually a single unit. For a two-handle faucet, each handle has its own cartridge or valve stem. The leaking side tells you which cartridge to replace. Do not attempt to disassemble the valve until you have shut off the water supply and released pressure by opening the faucet.

Water dripping from the base of a kitchen faucet handle onto the sink

Inspect the Sprayer and Hose Connections

A leak from the pull-out sprayer or the sprayer hose is a separate problem from the main faucet body. If water drips from the sprayer head after you release the trigger, the sprayer's internal diverter or shut-off valve may be worn. If water leaks where the hose connects to the faucet or under the sink, the hose connection or the hose itself is likely the issue.

Run the sprayer for a few seconds, then turn it off. Dry the sprayer head and the hose. If water continues to drip from the sprayer head, the sprayer assembly needs replacement. If the leak is under the sink, check the threaded connections where the hose attaches to the faucet and to the water supply lines. Tighten them with an adjustable wrench, but do not overtighten.

A cracked or kinked hose can also leak along its length. Pull the hose out fully and inspect it for splits, bulges, or worn spots. If the hose is damaged, replace it with the manufacturer's exact replacement part, not a generic hose, to ensure the fittings match.

Look Under the Sink: Supply Lines and Shutoff Valves

A leak that appears only under the sink, not on the countertop, points to the water supply lines, the shutoff valves, or the faucet's tailpieces. Water dripping from the supply line connections is usually caused by loose fittings, worn washers, or cracked compression nuts.

Wipe all connections dry with a paper towel, then turn the water on and off several times. Feel each connection point for moisture. If the leak is at the shutoff valve, tighten the packing nut slightly or replace the valve's washer. If the leak is at the supply line connection to the faucet tailpiece, tighten the nut or replace the supply line.

Also check the underside of the sink deck for moisture around the faucet's mounting nuts. A slow leak from the faucet base can travel down the shank and appear under the sink, even when the top looks dry. Run the faucet and watch for drips from the mounting area.

Distinguish Dripping from Condensation or Splash

Not every water droplet is a leak. Condensation on cold water pipes or the faucet body can form during humid weather, especially if the water is cold. This can look like a leak but is not a plumbing failure. Wipe the surface dry; if the water reappears without the faucet being used, it is likely condensation.

Splash from normal use can also be mistaken for a leak. If you notice water around the base after washing dishes, test by running the faucet without placing anything under it. Dry the area and observe. A true leak will appear even when the faucet is not in use or will drip continuously from a specific point.

To confirm a leak, place a dry paper towel under the suspected area and leave it for several hours. If the towel stays dry, the source is likely splash or condensation. If it becomes damp, you have a genuine leak that needs repair.