How To Fix A Leaking Sink?
QUICK ANSWER
Fix a leaking sink by identifying where the leak is coming from: the faucet (worn cartridge or O-ring), the drain assembly (loose lock nut), or the P-trap underneath (loose slip nuts). Each location has a different fix that usually takes under an hour.
Sink leaks come from a small number of common locations, each with a specific fix. The trick is identifying where the water is actually coming from since water runs along pipes and surfaces before dripping at a visible spot. Most sink leaks are DIY fixes under 30 dollars in parts. Here is how to diagnose by location and the right repair for each.
Where is the leak coming from?
Dry everything under and around the sink with paper towels. Run the water and watch carefully for the first sign of moisture. Common locations: dripping from the faucet spout (worn faucet internals), leaking at the base of the faucet (worn O-rings), pooling around the drain on top (loose drain lock nut), dripping under the drain (loose drain seal), and dripping from the P-trap (the curved pipe under the sink, with leaks at the slip nut connections). Each tells you where to focus.
How do you fix a leaking faucet?
For a faucet that drips from the spout when off, the cartridge or seat inside is worn. Turn off the water supply valves under the sink, remove the faucet handle (usually one set screw under a decorative cap), and pull out the cartridge. Take it to a hardware store to match a replacement (Moen, Delta, and Kohler all sell brand-specific replacement cartridges for 15 to 40 dollars). Reverse the disassembly to install the new cartridge. For leaks at the faucet base, replace the O-rings instead (a few dollars).
How do you fix leaking pipes under the sink?
The P-trap is the U-shaped pipe under the sink with slip nuts at each connection. Slip nuts loosen over time and start dripping. Hand-tighten the slip nuts first; if that does not stop the leak, disassemble the trap and replace the washers inside (they look like beveled rubber rings). For corroded metal P-traps in older homes, replace the entire P-trap with a new PVC version (5 to 10 dollars at any hardware store, 15-minute job with a slip nut wrench or channel-lock pliers).
When should you call a plumber?
Call a plumber if you cannot identify the leak source after careful inspection, if water is leaking inside the wall (you see staining or hear dripping in the wall), if the supply valves under the sink will not shut off, or if you have galvanized or copper pipes that need to be soldered. Also call if you have a leak after attempting a fix and the new connection still leaks; this usually indicates damaged threads or a fitting that needs professional replacement. Most other sink leaks are DIY.
Sink leaks come from the faucet, the drain assembly, or the P-trap, each with a specific fix. Dry everything, run water, and trace the actual source before disassembling. Faucet drips usually mean a worn cartridge (20-dollar fix). P-trap leaks usually mean loose slip nuts or worn washers (a few dollars). Call a plumber for wall leaks, soldered pipe issues, or anything you cannot diagnose.
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