leaky pipe under kitchen sink driving me nuts

Had the same issue last month... turned out it was the rubber gasket inside the slip joint connection that had worn out. Quick fix:

- Shut off water supply.
- Unscrew the slip joint nut.
- Replace old gasket (cheap at any hardware store).
- Reassemble and gently tighten.

Leak stopped immediately.

Yeah, replacing the gasket usually does the trick, but honestly, I've seen cases where it's not always that straightforward. Had a similar issue at a client's place a while back - thought it was just the gasket too, but after swapping it out, the leak persisted. Turned out the slip joint nut itself had a tiny hairline crack that was barely visible. Took me forever to spot it.

So, if you replace the gasket and still see dripping, give the nut itself a good look-over. They're cheap enough to replace anyway, and it'll save you from pulling your hair out later. Also, don't overtighten when you reassemble - just snug it up gently. I've seen folks crank down on those fittings thinking tighter is better, but that can actually deform the gasket or crack the nut.

Anyway, good luck with it... plumbing issues are always a bit of trial and error.

"Also, don't overtighten when you reassemble - just snug it up gently."

Wish I'd read this advice sooner... I learned the hard way that tighter isn't always better. Ended up cracking two slip joint nuts before realizing my Hulk-strength was the issue, not the fittings themselves. 😂 Anyway, hang in there - plumbing can be a real patience-tester, but once you nail it, you'll feel like a DIY champ. You've got this!

Yeah, overtightening got me too once. Ended up replacing the whole trap assembly - lesson learned. If seals look worn, swapping them out is cheap and easy enough. Worth a shot before calling in backup.

Did you use plumber's grease on the seals when you replaced them? I've found it helps keep things watertight longer... saves a few bucks down the road.

"Did you use plumber's grease on the seals when you replaced them? I've found it helps keep things watertight longer... saves a few bucks down the road."

Good tip - I swear by plumber's grease myself. But honestly, I've noticed even with grease, if the seals aren't seated perfectly or if the pipe alignment is slightly off, leaks tend to come back sooner or later. Did you double-check the alignment when you replaced them? Sometimes just adjusting the pipes slightly or using slip-joint washers can make a surprising difference...

Had pretty much the same issue when I moved into my first place. Thought I was being smart by using plumber's grease on the seals, but after a week or two the leak came back. Turns out alignment really was the culprit. Even with everything greased up, if those pipes aren't lining up just right, you're fighting a losing battle.

Here's what finally worked for me: I took everything apart again (yeah, annoying), cleaned the threads and seals thoroughly, then loosely connected everything without tightening completely. Once it was all loosely in place, I adjusted each section little by little until everything lined up naturally without forcing anything into place. Then tightened it all down evenly - bit by bit, alternating sides. Took a bit of patience, but it hasn't leaked since.

So yeah, grease helps, but alignment is key. Worth checking that out if the problem keeps coming back...

Did you by chance check if the pipes themselves had shifted or settled? Had something similar happen after redoing my kitchen cabinets. Turns out the weight of the new sink caused a slight shift downward, throwing off alignment. Ended up shimming the underside just a bit before reconnecting everything. No leaks since... might be worth a quick look underneath to see if anything's moved around?

Yeah, I had a similar issue when I moved into my first place. Thought I'd be all handy and replace the faucet myself - big mistake, lol. Turns out the pipes underneath weren't exactly thrilled with my DIY skills and shifted just enough to cause a slow, maddening drip. Took me forever to figure it out because everything *looked* fine at first glance.

Definitely agree it's worth checking underneath carefully. Sometimes even a tiny shift can mess up alignment enough to cause leaks. Also, double-check the seals and washers while you're at it. When I finally got under there (with my trusty flashlight and questionable plumbing skills), I noticed one of the rubber washers had gotten pinched slightly during installation. Replacing that little washer made a huge difference.

Oh, and pro tip from experience: don't overtighten connections thinking it'll seal better - been there, done that, ended up cracking a plastic fitting. Lesson learned the hard way.

Anyway, good luck! Plumbing issues are always frustrating, but you'll feel like a champ once you finally nail it down... or at least that's what I tell myself every time I'm crawling around under the sink again.

Good points overall, but honestly, sometimes it's not even worth messing around with washers or seals if you're not 100% sure. I've seen plenty of cases where folks spend hours troubleshooting a tiny leak only to realize the actual pipe threads themselves were worn or stripped. If you've checked everything else and still have issues, might be worth swapping out the whole fitting or pipe section. Costs a bit more upfront, but saves you from crawling under there every weekend... trust me on this one.

Can you tell which connection the water is actually coming from? If it’s a slip joint on the larger drain pipe, I’d focus on the washer, alignment and condition of that joint. A pressure regulator won’t fix an ordinary drain-joint seal.

The smaller pressurized supply connections are a different part of the system. Drying the outside and watching where the first moisture appears can help distinguish them without loosening anything. A clear photo of the leaking connection would make the next step much less of a guessing game.

Locating the exact joint first makes sense. On a slip-joint drain connection, the washer and its seating do the sealing; extra tightening or a regulator on the water supply won’t correct a damaged or misaligned seal. Follow the instructions for the actual drain parts, especially if they’re plastic.

If the leak is instead on a shutoff valve or faucet supply connector, say so before using drain-repair advice. The photo and whether it leaks only while the sink is draining would be useful clues.

For comparison, pressure is something to investigate if the problem is on the pressurized supply plumbing. That would need an actual measurement and an assessment of the system before deciding whether a regulator is needed.

I wouldn’t carry that explanation over to a leaking drain trap, though. For the original sink question, confirming which pipe and joint are leaking comes first.

For the supply-pressure side of this discussion, ours was high. We installed a regulator and I haven't had a leak since, but I wouldn't take that as a diagnosis of the original poster's drip or as a fix for a drain joint. Finding the exact leaking connection still comes first.

I do kind of miss my weekly chats with Dave in the plumbing aisle, though. Nice guy, even if I'd rather not have a standing appointment there!

Wait, installing a regulator fixed it completely? I've been battling a similar leak under my sink for weeks now, but our water pressure seems pretty normal... at least I think it is. Maybe I should double-check that before I call Dave's cousin or whoever my local plumbing guy is. But honestly, aren't those weekly plumbing aisle chats kinda pricey therapy sessions? Maybe I'll just keep the leak and save on counseling fees, lol.

Honestly, before jumping to regulators, have you tried the paper towel trick? Dry everything thoroughly under there, line it with paper towels, and just watch where the dampness starts. Might save you from another pricey "therapy" session at the hardware store... Any chance it's just a sneaky gasket issue?

"Any chance it's just a sneaky gasket issue?"

Could be, but from experience, sometimes the gasket isn't the only culprit. I've seen cases where the pipe itself had tiny hairline cracks - almost invisible until you really inspect closely. The paper towel trick is solid advice, but I'd also recommend running your fingers along the pipe slowly after drying it off. Sometimes touch reveals what eyes miss... and catching a small crack early can save you bigger headaches down the line.

"Could be, but from experience, sometimes the gasket isn't the only culprit."

Yep, agreed. Had a similar issue last year - thought it was just the gasket, swapped it out, and surprise... still leaking. Turns out the pipe had a tiny hairline crack right near the fitting. Took forever to spot it. Definitely worth a thorough check before you start buying parts you might not need. Pipes can be sneaky little devils sometimes.

"Pipes can be sneaky little devils sometimes."

Haha, ain't that the truth... Had a similar headache myself a while back. Thought it was just the gasket too, but nope - turned out the joint itself was warped just enough to keep dripping. Took me ages to figure out because it looked totally fine at first glance. Definitely pays to slow down and double-check everything before you start tossing money at new parts.