Bucket or shallow pan
Use it for: Catches the water left in the trap when you open the drain connection.
Shop buckets and drain pansKitchen sink drain repair
How to Replace a Kitchen Sink Slip Joint Washer Set
If your kitchen sink drain is dripping from a slip-joint connection, replacing the slip joint washer set is often the right fix. The job is usually just loosening the nut, swapping the worn washer, and reassembling the joint cleanly.
This repair works best when the leak is coming from a hand-tightened or nut-tightened drain joint under the sink, especially around the trap or tailpiece connection. Start with a dry inspection so you know which joint is actually leaking before you take anything apart.
Before you start: Match the replacement part to your exact kitchen sink before ordering.
Safety first
- Wear gloves if the trap water is dirty or you are cleaning buildup from old drain parts.
- Support the drain assembly while loosening nuts so you do not crack older plastic piping.
- Do not overtighten slip-joint nuts. Too much force can deform the washer or crack the nut.
Tools you may need
Channel lock pliers
Use it for: Helps loosen or snug slip-joint nuts that are stuck or too tight for hand turning.
Find channel-lock pliers
Old towel or rags
Use it for: Lets you dry the pipes, wipe the joint clean, and spot fresh drips during testing.
Shop shop towels or rags
Flashlight or work light
Use it for: Makes it easier to see the exact joint that is leaking under the sink.
Find a small work light
Small nylon brush or old toothbrush
Use it for: Cleans residue from the pipe and nut so the new washer can seat properly.
Shop small cleaning brushesAs an Amazon Associate I earn from qualifying purchases. Repair Riot may earn a commission at no extra cost to you.
Step-by-step fix
Step 1: Confirm the leak is at a slip-joint connection
- Empty the cabinet so you can see the full drain assembly under the sink.
- Dry the trap, tailpiece, and nearby joints with a towel.
- Run a small amount of water, then watch for the first place a drip forms.
- Look for water beading around a slip-joint nut where two drain pieces meet, not from the sink basket above or a cracked pipe wall.
If it works: You have traced the leak to a slip-joint connection under the sink.
If it doesn’t: If the water starts higher up at the sink basket, faucet, dishwasher branch, or from a split pipe, this washer replacement is probably not the right repair.
Stop if:
- The drain pipe is cracked, badly corroded, or missing pieces.
- The leak is coming from inside the cabinet wall or another hidden plumbing area.
- The trap or connected piping feels loose because the wall stub-out or sink drain assembly is damaged.
Step 2: Set up the area and take the joint apart
- Place a bucket or shallow pan under the trap.
- Loosen the leaking slip-joint nut by hand. If needed, use pliers gently so you do not crush plastic parts.
- Pull the joint apart slowly and let the trapped water drain into the bucket.
- Remove the old washer and keep it nearby so you can compare its size and shape to the replacement.
If it works: The leaking joint is open and the old washer is removed.
If it doesn’t: If the nut will not move, dry it off and try again with pliers while supporting the pipe with your other hand to avoid stressing the assembly.
Stop if:
- The nut is cracked and will not tighten back down.
- The pipe end is chipped, out of round, or too damaged for a new washer to seal.
Step 3: Clean and inspect the mating surfaces
- Wipe the inside of the nut, the pipe end, and the sealing surface clean.
- Use a small nylon brush to remove grime, old residue, or mineral buildup.
- Check that the pipe end is smooth enough for the new washer to seat evenly.
- Compare the new washer to the old one and choose the matching size and style from the set.
If it works: The joint surfaces are clean and you have the correct replacement washer ready.
If it doesn’t: If the replacement washer does not match the old one closely, pause and get the correct size before reassembling.
Stop if:
- The pipe sealing surface is deeply gouged, warped, or split.
- You find hidden damage that a new washer will not cover or compress against.
Step 4: Install the new slip joint washer
- Slide the slip-joint nut onto the pipe if it came off during disassembly.
- Place the new washer on the pipe in the same orientation as the old one, with the tapered side facing into the joint on most standard slip connections.
- Bring the two drain pieces back together so they sit straight and fully aligned.
- Thread the nut on by hand first to avoid cross-threading.
- Hand-tighten the nut until snug, then give it a small additional turn with pliers only if needed.
If it works: The new washer is installed and the joint is reassembled straight and snug.
If it doesn’t: If the nut binds or the pipes do not line up naturally, back it off and realign the joint before tightening again.
Stop if:
- The nut will not thread properly because the threads are stripped or cross-threaded.
- The pipes only meet if you force them into position, which usually means another section is misaligned.
Step 5: Test for drips and fine-tune the joint
- Dry the repaired joint completely so new moisture is easy to spot.
- Run cold water for about 30 seconds while watching the joint closely.
- If it stays dry, run a stronger flow for another minute.
- If you see a slow drip, tighten the nut just a little more and test again.
If it works: The joint stays dry during a steady water flow test.
If it doesn’t: If the drip continues after a small adjustment, take the joint back apart and check washer orientation, fit, and pipe alignment.
Stop if:
- Water is now leaking from a different nearby joint because the assembly shifted.
- The joint still leaks after reassembly with the correct washer and proper alignment, suggesting the nut or pipe section also needs replacement.
Step 6: Make sure the repair holds in normal use
- Fill the sink partway and let it drain to put a fuller load through the trap.
- Check the repaired joint with both a flashlight and a dry finger or paper towel.
- Look again after 10 to 15 minutes for any slow seepage.
- Put the cabinet items back only after the area stays dry.
If it works: The repair holds under normal sink use with no drips or seepage.
If it doesn’t: If moisture returns later, inspect the joint again and replace any damaged nut or misaligned drain section that kept the washer from sealing.
Stop if:
- You notice repeated leaking along with movement in the drain assembly, cabinet damage, or signs of a larger plumbing problem.
Replacement Parts
Find a kitchen sink slip joint washer set on Amazon
Match the replacement part to your exact kitchen sink before ordering.
As an Amazon Associate I earn from qualifying purchases. Repair Riot may earn a commission at no extra cost to you.
Verify the repair
- The repaired slip-joint connection stays dry during a light flow and a full sink drain-down.
- The nut is snug and the pipes are aligned without being forced sideways.
- No new drips appear at nearby joints after the sink has been used normally.
FAQ
How do I know the slip joint washer is the problem?
A bad slip joint washer usually causes dripping right at the nut where two drain pieces join. If the leak starts higher up at the sink drain basket or from a crack in the pipe, the washer is not the main problem.
Do I need sealant or plumber's putty on a slip joint washer?
Usually no. Slip-joint washers are meant to seal by compression when the joint is clean, aligned, and tightened correctly. Adding sealant can make the joint harder to assemble and does not fix a wrong-size washer or damaged pipe.
Which way does the washer face?
Most standard slip-joint washers install with the tapered side facing into the joint and the flat side toward the nut. If you saved the old washer, match its orientation unless it was clearly installed wrong.
Why is it still leaking after I replaced the washer?
The most common reasons are the wrong washer size, backward washer orientation, dirty sealing surfaces, cross-threaded or cracked nuts, or pipes that are out of alignment. A damaged pipe end can also keep the new washer from sealing.
Can I reuse the old slip-joint nut?
Yes, if the nut is not cracked and the threads are in good shape. If it is split, stripped, or badly warped, replace it so the new washer can compress evenly.