Mystery Leak. I'm stumped.

**IndyBob** · 08-04-2012, 01:21 PM

Above my kitchen is a full bath that has a tub on one side, two sinks and a toilet on the other. Starting a couple days ago it started dripping from the kitchen cabinets that are approximately beneath the tub. Since my 14-year old daughter was taking a shower, I figured that she just didn't close the curtain all the way. After letting things dry until the weekend, I decided to try to narrow down the leak. I filled and drained each sink several time with no problems. Then I flushed and flushed and flushed the toilet (6 times) with no problems. After waiting about an hour, I decided to turn on the tub and let it run free for 10 minutes. No problem. I used both the spout and shower head to fill and verified that it was a caulk or tile grout issue. So, I filled the tub half way and while it was draining, I flushed the toilet. Everything seemed to work OK, but the dripping came back. I had problems with the toilet years ago, when I discovered that it needed extension rings to match the height of the ceramic tile. These fixed it, but at that time, it was dripping in a different place, directly below the toilet. So, I figured that it must be the tub's p-trap. Cut a hole in the kitchen ceiling and found that all of the piping was completely dry. I can also get to the back of the tub from upstairs and everything was dry there too. In fact, I could see the entire 5' lateral run to the exterior wall, which was dry. The cabinets were one joist bay over, which I didn't open.

So, before I do more damage to the kitch ceiling, where might the leak be? If it is the toilet, the water is making an odd trip to get to the kitchen. I went ahead and cleaned all the pipes with lye to ensure that all of my daughter's hair was out of them, which made everything drain faster, but hasn't changed the leak. (No, I don't use lye that often and don't leave it in the pipes so that it can eat away the bottom of the pipes.) My fear is that there is some sort of decayed pipe where the lateral meets the stack, but that would be a royal pain to get to. I would pull the toilet, but I just don't know how that could be an issue since it isn't leaking at the toilet or underneath it.

Any ideas?

Thanks,

Bob

**jadnashua** · 08-04-2012, 01:33 PM

Water can flow a long ways before it finds a low or weak spot to drip out. Does the toilet rock at all when you sit on it? Can you notice it moving at all if you push it a little either front to back or side to side? If so, the seal is broken. A toilet cannot rock or it will break the wax seal. Then, with extension rings, how did you seal between it and the flange? That's another critical step.

You might be able to rent an inspection camera - these have the sensor on a long, flexible stalk. It would let you see more places with less damage than tearing out lots of drywall.

**IndyBob** · 08-04-2012, 01:52 PM

Originally Posted by jadnashua

Water can flow a long ways before it finds a low or weak spot to drip out. Does the toilet rock at all when you sit on it? Can you notice it moving at all if you push it a little either front to back or side to side? If so, the seal is broken. A toilet cannot rock or it will break the wax seal. Then, with extension rings, how did you seal between it and the flange? That's another critical step.

You might be able to rent an inspection camera - these have the sensor on a long, flexible stalk. It would let you see more places with less damage than tearing out lots of drywall.

The toilet doesn't rock in the least. Not even a little jiggle. Probably because I had a professional plumber (now retired) set this when it was leaking last time. I know that he used three white plastic 1/4" risers. These were screwed down into the subfloor through holes in the original flange. They were "buttered" up with wax when set, so they should be pretty solid. I don't recall if the new wax ring had a plastic horn or not. The toilet is not caulked to the tile floor and there is no water on the floor. Also, the can light fixtures that are near, but not directly under, the toilet don't drip and that is where it leaked last time and also they are between the toilet and where the water is coming from the cabinets. I'm guessing that you can see why I don't want to pull the toilet; I'm just not that good at putting them back. The really odd thing is that the leak only seems to come when the tub is draining while the toilet is flushed. I was thinking that there may be a partial clog, but there is never any sort of a backup. Once I used the lye, both sinks and the tub drain so fast they create a vortex. I was considering using sulfuric acid, but not until I am sure that everything is fully rinsed from the lye. I'm not a plumber, but have been in construction for over 25 years and have chased may water leaks, both from plumbing and water infiltration and have seen leaks show up hundreds of feet from the source, so I understand what you are saying, but I'm not yet sure where to attack next. Thanks.

hj · 08-05-2012, 09:04 AM

Turn on the tub valve and hold your hand in the water flow and direct it against the tub's overflow plate. That will usually cause the leak to occur.

**IndyBob** · 08-05-2012, 10:07 AM

Originally Posted by hj

Turn on the tub valve and hold your hand in the water flow and direct it against the tub's overflow plate. That will usually cause the leak to occur.

The problem is that I can see the back of the overflow, valve, and the entire trap and it isn't leaking at any of them. The tub is parallel with the joists, which are 16" o.c. and I can see were the 2" copper waste line goes from the front of the tub, directly under the tub, to the outer wall. It is all dry there. Then there are a pair of 45's that direct the line to the next joist space, which I haven't opened up (I am trying to avoid a Swiss cheese kitchen ceiling.) The line runs laterally along the outside wall, but not in the wall. It crosses 6 joist cavities, then, I assume, connects at a wye. The wye is at the stack. I'm guessing that there is a double-wye immediately beneath this that picks up both toilets, which are back-to-back.

Also, I just got it to start leaking by only running the tub, wide-open, without letting it fill the tub at all, and not using either toilet or any of the three sinks, or shower, that use the stack.

**IndyBob** · 08-05-2012, 11:16 AM

Well, crap, I found where the leak is by cutting a second hole. It's neither the tub nor the toilet. It is the 2" pipe that is coming from the tub. Of course it is inbetween joist spaces, directly above the kitchen cabinets, and, of course, the cabinets were built with a 2x12 bulkhead, so there's no going through the face of the bulkhead or the ceiling to get there. This is going to be one of those plumbing repairs that is 2% plumbing and 98% carpentry.

Thanks for the ideas, though. Bob