Stop Your Kitchen Sink P-Trap Leak
Is your kitchen sink p-trap leaking after replacing a nut? Learn how tight the nut should be, and avoid cracking plastic parts or causing leaks.
A leaking kitchen sink p-trap is a headache many homeowners face. Often, the cause is a worn or cracked nut that holds the trap together. You may be wondering how tight these nuts really need to be. Tightening too little causes leaks. Tightening too much can split the nut.
Question:
Does the large nut on a kitchen sink p-trap need to be very tight? How can you tell when it’s enough vs. too tight?
Answer:
The nut should be hand-tight plus about one-quarter to one-half turn with pliers. This is enough to compress the slip joint washer and create a seal. Overtightening can split plastic nuts or deform the washer, leading to leaks.
The seal in a p-trap joint is made by the tapered washer, not the nut threads. The washer must sit clean and straight. Silicone grease on the threads won’t hurt, but isn’t required. Do not use Teflon tape or pipe dope.
After tightening, run water in the sink for a few minutes. If drips appear, gently turn the nut another eighth turn. If leaks continue, disassemble and reseat the washer. Sometimes replacing the entire p-trap assembly is the best solution, especially for older plumbing.
For more helpful details, see this Family Handyman guide on fixing traps. You may also want to check this Home Depot tutorial on p-trap installation.
I’m Chris Mayer, writing for Plumbing 101.
