Leak inside kitchen wall, water appears in basement
May 26, 2010 8:36 PM   Subscribe

Leak in basement whenever water goes down kitchen sink drain, probably leak inside wall since under sink I cannot find any drips. Please prepare me for how bad this may be ($$$) and how to deal with plumber. Many details inside.

I have Googled and searched metafilter, but most advice is about visible leaks, I believe mine is inside the wall.

Kitchen double sink, left side garbage disposal, right side simple tail piece. Both sides eventually go to a Y that is soldered to the copper drain pipe going into the wall. Since there is a window over the sink and from looking in the basement I believe the vent pipe is in the right corner of the kitchen. The leak manifests itself by coming through the floor hole where the cold water pipe goes up from the basement. I suspect it's just the nearest hole under the drain pipe leak.

Since I could not find any leak under the sink but we're still getting water dripping into the basement, I conducted an experiment. I waited until there was no more dripping in the basement, then I put a drain stopper in the non-garbage disposal side and started the water running. No dripping in the basement. I then had my wife pull out the stopper, and got lots of dripping almost instantly. That says to me drain side, not supply. And still no drips under the sink itself.

I know, I have a leak and it must be fixed. But this is a modern-ish kitchen, with long formica countertop, backsplash, oak cabinets, etc. So, kind metafilter folks, please advise me on the steps to take in the right order, and how to deal with the plumber.

Specifically, tomorrow morning I can call out from my job and start hacking at the back of the cabinet under the sink and then into the drywall. I can also call a plumber first (since they're unlikely to come out instantly). I am assuming I want to make it as easy as possible for the plumber to see what he is up against. But of course there's a limit to how far right I can go. The kitchen cabinet will end and I will then be into corner cabinet territory. At some point somebody (probably me) would have to start disassembling the kitchen. And as bad luck would have it in the basement there is the laundry sink and hot water heater directly below all this, complicating access for the plumber down there. And this is Memorial Day Weekend coming up in the USA.

I assume plumbers are not miracle workers and can only do so much reaching through a kitchen cabinet with two doors (i.e., the opening under the sink is in two halves, not one large door).

We have not needed a plumber in many years, and never for anything that might be this involved. Any advice about plumber selection also appreciated.

I realize things may not be as bad as I fear, but I just want the best advice in case it is. Thank you all very much in advance!
posted by forthright to Home & Garden (9 answers total) 1 user marked this as a favorite
I suspect you'll need a carpenter as well as a plumber.
posted by Chocolate Pickle at 8:51 PM on May 26, 2010

O.K., first you have probably had this leak for months if not years. While it bothers you, it does not have to be fixed by tomorrow night. Second, you will know a lot more once you expose the plumbing under the sink.

I would wait until Saturday and then use a circular saw with just a 1/4" of blade exposed to cut a foot-square hole through the panel in the back of the cabinet. Now, using a utility knife, cut away the drywall from within the area of the hole you just cut in the cabinet. Now, at least, you can look inside the wall and see what is going on when you run the water. You may find that the drain is leaking right where it enters the wall, or that it is leaking well down the wall.

This is the time to decide whether you need a plumber. If so, you can call him (or her) on Tuesday or call Saturday to schedule a Tuesday appointment.

This is also the time to look into the wall and get an idea of where the pipe is going. It might be going straight down, off to the side and then down, or... This will also give you an idea where it might be as it enters the basement wall. Use the same minimal-depth approach to cutting into the basement wall and see if you can find the pipe. Now, is it leaking where you can see it? Does it look like something you can fix?

Start there before contemplating tearing out any part of the kitchen. This may turn into a very simple fix for both you and the plumber. If it is, when it is done just cover the hole in the back of the cabinet with a false panel and shut the doors. You may want to use the same approach to covering the hole in the basement wall.
posted by Old Geezer at 9:01 PM on May 26, 2010

If it's been leaking for years, there will be wood damage. It could be structurally significant, and you'll need a carpenter to know for sure.
posted by Chocolate Pickle at 9:21 PM on May 26, 2010

Thanks Old Geezer. Your advice sounds wise and just what I was hoping for. Two things I did not mention (darn, and I was trying to be complete) are the basement is not finished, just cement block. *But* the house circuit breaker box is mounted on that wall so I do not want to just ignore this.

I think you are right, based on stains on the cement block and floor, this is probably not brand new, just noticed tonight. The drip out of the kitchen floor supply pipe hole hits the top of the cement block wall and then meanders down the wall near the breaker box and then to the floor next to the water heater.

And I suppose we can eat off paper plates for a while and wash pots and pans in a bucket.

Thanks for calming me down.

And Chocolate Pickle, I guess a plumber might eventually be needed, we'll see.
posted by forthright at 9:23 PM on May 26, 2010

Darn, I should have used preview. Therefore, Chocolate Pickle, I missed your second comment. Because the basement is unfinished and I can clearly see the underside of the wood, and know this puddle was not there a couple weeks ago (when I did a load of laundry myself), I doubt there would be structural damage that quickly from a drain leak (as opposed to a supply side leak).

Also, my reply was mistyped...I meant to agree with you that a *carpenter* might eventually be needed, depending on what is seen when the area is opened up more.

Sorry again for violating the preview rule.
posted by forthright at 9:32 PM on May 26, 2010

If you are willing and able to open that wall, you can probably handle the problem yourself.

If you can get through the cabinet and see what's in there (a good trick for this is to reach in with a digital camera and take pictures from a bunch of angles) you should be able to find the leak and deal with it temporarily (for weeks-to-months of "temporary") with silicone rescue tape, which is awesome.

But leaks don't generally just spontaneously happen, you know? Has something in your house shifted? If this is a new thing as you say, you might want to consider snaking the drain first; could be the problem isn't a leak spontaneously appearing, but rather water that's backing or not flowing out as quickly as it should.

After that, on your own time and assuming it's all PVC drain pipe, pick a to clean it all off and wait for it to dry, then re-seal the joint with the correct epoxy. It's really not hard to do.
posted by mhoye at 7:02 AM on May 27, 2010

Update: used Dremel tool to cut out a small section of the cabinet back, then cut through drywall (about 4" high x 10" wide opening). The drain pipe turns right after entering the wall (toward vent stack). This is all copper. The copper drain pipe looks like it is touching the cold water supply line, and there seems to be oxidation on the drain line, and that's where it seems to be leaking.

I contacted a plumber recommended by neighbor and described all this to him. He said no need to open wall up any larger for now. He wants to see situation first. Appointment for Friday morning.

@mhoye: House is about 40 years old. I don't see any obvious signs of settlement in that area. Silicone rescue tape sounds like a good idea. I'll ask plumber if that would help for the short term if he can only look and not fix on Friday.
posted by forthright at 7:23 AM on May 27, 2010

From your description, I'm wondering if the drain line, rubbing against the supply line, with the disposal vibrating every time it is turned on, hasn't just rubbed a hole in itself. Got a dentist's mirror? If that is the case, be sure the two lines are not rubbing against each other before you close up the wall. A simple solder patch might work on the drain line (although I'm guessing it is brass rather than copper) and a little piece of electrical tape to isolate the two pipes from one another might just do the job. A good plumber should be able to braze brass if it is just a little hole. It is not under pressure, so all it needs is to be sealed.
posted by Old Geezer at 11:15 AM on May 27, 2010

OK, plumber was here this morning and gave verdict: the copper drain pipe has a split that runs right down its length...we don't know exactly how far because it continues into the enclosed portion of the wall behind the corner cabinet. He believes this is because the kind of copper ("M") was inferior for the application.

At this point he said he (and I) needed to "stop work" and contact my insurance company. I have done this, but the adjuster probably will not be out until Tuesday or Wednesday due to the holiday weekend. Meantime it's paper plates, plastic cups and utensils.

I hear from the plumber and from friends that in this kind of instance normally I will be out the deductible and the cost of actually getting the pipe(s) repaired in the wall, but that the work to expose the pipes and repair the damage caused by exposing the pipes will be born by the insurance.

At the insurance company's suggestion I have also contacted an electrician to inspect the safety of the circuit breaker box that had water dripping on it for a time.

I appreciate everyone's help, and hope that this thread may benefit someone else in the future who is in the same situation!
posted by forthright at 5:43 PM on May 28, 2010

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