Most Likely Causes (Ranked)
Most modern kitchen faucets use a ceramic disc cartridge that controls both temperature and flow. After 5-10 years, the ceramic discs develop microscopic scoring from mineral particles in the water. The O-rings around the cartridge body harden and crack. The result: water drips from the spout when the handle is off, or water seeps around the base. Moen uses the 1225 or 1255 cartridge, Delta uses the RP46074, Kohler uses model-specific cartridges.
Two-handle faucets (and some single-handle Delta models) use spring-loaded rubber seats pressed against a valve seat by water pressure. The rubber cup deteriorates, the spring loses tension, and the valve seat corrodes from hard water. Delta seats and springs kits are $4-6 and fix 90% of Delta drips.
O-rings at the base of the spout body create the seal that prevents water from seeping out around the base when the faucet is running. Kitchen faucets with swiveling spouts wear these O-rings faster because every pivot grinds the rubber against the housing. Pull-down faucets are especially prone because the spout movement adds stress.
The brass valve seat inside the faucet body is the surface the washer or cartridge seals against. Hard water deposits and mineral corrosion create pits in this surface. A new washer or cartridge can't seal against a pitted seat. You can regrind the seat with a seat wrench ($10) or replace it if it's removable.
Pull-down and pull-out faucets have a hose running through the spout body. The weight and repeated pulling stresses the spout connection to the deck. Over time, the mounting hardware loosens, the spout develops play, and water seeps through the loosened base gasket. The retaining nut under the sink may need tightening.
How to Fix It
Replace Cartridge (Single-Handle)
$15-35 DIY / $150-250 Pro- 1Turn off both hot and cold shut-off valves under the sink. Open the faucet to drain residual water.
- 2Remove the handle: look for a set screw under a decorative cap (use an Allen key, usually 3/32 or 7/64 inch).
- 3Remove the cartridge retaining clip or nut. Pull the cartridge straight out (Moen cartridge puller tool is $15 and makes this much easier).
- 4Take the old cartridge to the hardware store to match. Install the new one in the same orientation.
- 5Reassemble and test both hot and cold. If hot/cold are reversed, rotate the cartridge 180°.
Replace Seats and Springs (Delta/Two-Handle)
$4-8 DIY- 1Turn off water. Remove the handle and the cam/packing nut.
- 2Lift out the ball (Delta) or stem. Use needle-nose pliers to pull the rubber seats and springs from the valve body.
- 3Press new springs into new rubber seats. Insert into the valve body holes.
- 4Reassemble. These kits are brand-specific — Delta RP4993 is the most common.
Replace Spout O-Rings
$5-10 DIY- 1Turn off water. Remove the spout by pulling straight up and twisting (or removing a set screw at the base).
- 2Note the O-ring sizes — take them to the store or order a faucet-specific O-ring kit.
- 3Coat new O-rings with silicone plumber's grease before installing.
- 4Press the spout back into the body and test.
When to Call a Professional
Know your faucet brand before buying parts — Moen, Delta, Kohler, and Pfister all use different cartridges.
Don't force a stuck cartridge — you can crack the brass valve body. Use penetrating oil and a cartridge puller.
If the faucet is 15+ years old and multiple parts are failing, replacing the entire faucet ($150-300) is more cost-effective.
How to Prevent It
Don't crank the handle — firm is enough. Over-tightening destroys seals faster.
Clean the aerator every 6 months (unscrew the tip) to prevent debris from reaching the cartridge.
Address drips immediately — a small drip indicates a seal that will only get worse.
Consider a water softener if you have hard water — extends cartridge life 50-100%.
Frequently Asked Questions
Repair if the faucet is under 10 years old and the fix is a cartridge ($15-35). Replace if it's 15+ years old, corroded, or you've already repaired it twice.
Look for a logo on the faucet body (often on the base). Check under the sink for labels on the supply lines. Moen has a flat handle nut, Delta has a ball mechanism, Kohler has a hex shape on the valve body.
Hot water seals fail first because heat accelerates rubber degradation. The hot-side cartridge or seat needs replacement.
Sometimes, but brand-specific cartridges seal better and last longer. Moen offers lifetime warranty on cartridges — call them for a free replacement.