How to Fix a Leaking Sink Drain
Updated February 20, 2026
Find and fix a leaking sink drain -- whether it is the basket strainer seal, the tailpiece connection, or the P-trap slip joints -- with the right fix for each failure point.
Overview
Water under the sink is never good news, but a leaking drain is one of the easier fixes in plumbing. The leak is coming from one of three spots: the basket strainer (where the drain meets the sink basin -- failed putty or gasket), the tailpiece (the vertical pipe between strainer and P-trap -- loose slip nuts or worn washers), or the P-trap itself (the U-shaped pipe -- same slip-joint issues or a corroded trap with pinholes). All three fixes are under $25 in parts and take less than an hour. The key is figuring out exactly which connection is leaking before you start taking things apart.
What You'll Need
Safety First
- Bucket under the sink before you loosen anything. The P-trap holds water on purpose (it blocks sewer gas), and loosening it dumps that water into the cabinet.
- Poured chemical drain cleaner down there recently? Wear rubber gloves and eye protection. Residual chemicals in the P-trap water will burn your skin on contact.
Step-by-Step Instructions
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Identify Exactly Where the Leak Is Coming From
Dry everything under the sink with a towel and lay paper towels or newspaper on the cabinet floor. Fill the sink with a few inches of water and pull the stopper. Watch where water appears on the pipes below -- that is your leak. Or run the faucet for 30 seconds while you watch from below with a flashlight. Three spots to check: the basket strainer body where it meets the underside of the sink, the tailpiece slip-joint nuts (where the tailpiece connects to the strainer or the trap), and the P-trap slip joints (the nuts at either end of the U-shaped section).
Tip: Leaks only when the sink is full of standing water? That points to the basket strainer putty seal. Leaks only when water is actively flowing? More likely a slip-joint connection under flow pressure. -
Fix a Basket Strainer Leak (Putty or Gasket Failure)
Water leaking from where the drain body meets the underside of the sink? The putty seal or gasket has failed. From below, loosen and remove the large locknut holding the strainer to the sink (slip-joint pliers or basin wrench). Pull the strainer out from above. Scrape all old putty from the sink opening and strainer flange -- putty knife first, then rubbing alcohol for the residue. Roll a fresh rope of plumber's putty about 1/2 inch thick around the entire drain opening. Press the putty onto the underside of the strainer flange, set it back in the opening from above, and from below reinstall the gasket, friction ring (if present), and locknut. Tighten until putty squeezes out evenly. Wipe the excess from above and wait an hour before using the sink.
Tip: If the strainer body is corroded or pitted (common on old chrome or brass), just replace the whole strainer assembly ($5-15). A corroded flange will never seal right no matter how much putty you use. -
Fix a Tailpiece or Slip-Joint Leak
Water dripping from a slip-joint nut? Try tightening it first -- hand-tight plus a quarter turn with pliers. If that does not stop it, the nylon washer inside the nut is worn, cracked, or sitting wrong. Loosen the nut and pull the joint apart. The old washer sits inside the nut with the tapered side facing down toward the pipe. Swap it for a new one -- 1-1/4 inch for bathroom sinks, 1-1/2 inch for kitchen. Tapered side faces the pipe connection -- the taper is what creates the seal when the nut compresses it. Reassemble, hand-tighten plus a quarter turn, and run water.
Tip: Washers are $1-2 for a multi-pack. Buy one with several sizes. The number one reason a slip joint leaks after reassembly is the washer going in backwards -- flat side toward the pipe instead of tapered. The taper makes the compression seal. -
Fix or Replace the P-Trap
Leak coming from the body of the P-trap itself, not the joints? It is corroded through. Chrome traps corrode from the inside -- pinholes develop that you cannot see from the outside until they start dripping. Put a bucket under the trap, loosen both slip-joint nuts, lower the trap, and dump the water. Bring the old trap to the hardware store to match the size (1-1/4 inch bathroom, 1-1/2 inch kitchen). Install the new trap with fresh washers. Hand-tighten both nuts plus a quarter turn. Go with PVC over chrome -- it costs less and will never corrode.
Warning: Make sure the new trap lines up with the existing tailpiece and wall pipe heights. If the alignment is off, you will need a tailpiece extension, slip-joint extension, or an adjustable P-trap. Bring a photo of your under-sink plumbing to the hardware store -- it saves a lot of guessing. -
Test All Connections and Verify
Fill the sink with several inches of water and release it all at once -- this tests every connection under maximum flow. Watch every joint, nut, and seal with a flashlight while it drains. Run the faucet for 2-3 minutes and check again. Dry everything one more time, lay a fresh paper towel under the pipes, and check back in an hour. Dry paper towel means the repair is good. If anything is still dripping, tighten slightly or check the washer alignment.
Tip: Smart move: put a small plastic tray or drip pan under the P-trap permanently. Even a perfect repair can develop a slow leak months down the road. The pan catches it early before it damages the cabinet floor.
Pro Tips
- Do not use silicone caulk on basket strainers -- use plumber's putty. Silicone bonds permanently, which seems better, but when the sink flexes (water weight, temperature changes, someone leaning on it) the rigid bond cracks. Putty stays pliable and moves with the sink.
- Hand-tighten all connections first, then go back and give each a quarter turn with pliers. That is it. Overtightening plastic slip-joint nuts cracks them. If it leaks at hand-tight plus a quarter turn, the washer is the problem, not the tightness.
- Kitchen sink with a garbage disposal? The disposal side uses a gasket and flange bolts instead of slip joints -- completely different setup. See our garbage disposal guide for those connections.
- When a chrome P-trap fails, replace it with PVC. Chrome corrodes from the inside in 5-10 years. PVC never corrodes, costs less, and nobody sees under the sink anyway.
- Sewer smell under the sink but no visible leak? Either the P-trap is dry (water seal evaporated from a rarely-used sink -- run water for 30 seconds to refill it) or the trap has a crack letting sewer gas escape.
When to Call a Pro
This is straightforward DIY. Call a plumber only if the leak is from the drain pipe inside the wall (not the visible connections), if the pipes are old galvanized steel crumbling at the touch, or if you need to reconfigure the drain layout for a new disposal or different sink.