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Our kitchen ceiling has a leak.

We have narrowed it down to it coming from the master bathroom shower. If one person takes a shower, it’s fine. If a second person showers shortly after or even a couple hours later, we get water leaking from the ceiling in the kitchen. Not a whole lot, but enough that has done damage to ceiling and leaves water on kitchen floor. Also sometimes if master bath shower turns on, and we flush toilet in master bath, it drips. We replaced shower pan less than a year ago, and it was ok for a few months but is now back.

  • What is the most likely causes of my leak?
  • How should I approach finding and fixing it?

closed as too broad by isherwood, Tyson, ThreePhaseEel, mmathis, Machavity Feb 21 '18 at 23:06

Please edit the question to limit it to a specific problem with enough detail to identify an adequate answer. Avoid asking multiple distinct questions at once. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

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    So it's not so much that the ceiling leaks as that your shower plumbing leaks. :) Sounds like it's in the collective drain. Unfortunately, as it is, your question is too broad for our Q&A format. Please dig into the repair and ask more specific questions when you have them. – isherwood Feb 14 '18 at 19:35
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    My thoughts are that it's not your kitchen ceiling which has a leak (since kitchen ceilings are typically not expected to hold water). It's your master bath drain plumbing which has a leak - and it's leaking onto your kitchen ceiling ... The more you use anything up there, the more water leaks, the more likely you are to see it coming through the ceiling. – brhans Feb 14 '18 at 19:36
  • ... "If one person takes a shower, it's fine..." Then problem solved, rotate shower duty. Actually, that was obvious sarcasm. Truth be told, it is NOT fine when one person takes a shower, but apparently enough water pools that it finds its way to where you can see it. How long has this been going on? At least a year you indirectly imply? Your bath is apparently above the kitchen... directly above it? Do you have any access panels to the plumbing? You need to get in there. Also, you will probably want to replace the drywall on the ceiling and inspect the rafters. Are you interested in a DIY? – noybman Feb 15 '18 at 4:26
  • "Any thoughts?" is a very vague question - are you asking what the problem could be? Or how you would replace or repair the shower's plumbing? Or something else? Please edit to clarify. – mmathis Feb 15 '18 at 14:25
  • Had that problem, turned out one person didn't know how to use the shower curtain and was flooding the bathroom floor... I suppose that wouldn't explain the toilet though – colmde Feb 15 '18 at 21:56
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Unfortunately, there could be multiple causes for this issue you are seeing. Without seeing the inside of the wall or the configuration of the waste/soil lines it might be impossible to give a definitive answer.

It is very likely the leak is always occurring when the water is running, it is just noticeable once the wall material become saturated to the point it cannot hold any more water, and then begins leaking into the room below.

I think is unlikely the drain pan for the shower is the culprit if the toilet is actually affecting the rate of water intrusion. The toilet would have to push enough water up the shower drain to fill the trap and flow into the pan. If it could do that, then you have another problem further down the soil line.

Given your description these are the places I would inspect:

Check for blockages. Even if a blockage is the culprit, there is still a problem. Ideally the overflow should appear in your fixtures first, not hidden behind the wall.

I would check the joints in the stack. Typically, a toilet soil line is separate from the waste line of a sink or shower until the soil stack, where they collect and run to the sewer. If a joint at the stack has failed, the waste water flowing through the fittings is seeping through the joint and down outside of the stack to the cut-out in the plate between the floors and then into the ceiling.

If the toilet and shower are sharing a drain line check the joints in this line too. Pay attention to the traps, while installing a new drain pan or toilet if too much force was applied it could have damaged the joints of either the shower or toilet. E.g. remodeled floor changes the rise of the toilet flange above the floor; new toilet is installed and tightened down, pushing against the soil line, stressing the joints and forming a leak. Cast iron is not forgiving of this abuse. Also check that the pipe is being supported at regular interval so it is not sagging and causing unnecessary stress to the joints.

Check that the shared line is sized for the flow, is sloped correctly, and doesn't run too far. If any of these factors are incorrect, air-locking can occur. This can decrease the amount flow the pipe can handle, which leads to water filling or backing up in the line until it breaches, say the toilet flange, where it flows over the flange edge and down the pipe into the space below, all hidden by the toilet pedestal itself. Your pipe should not have a slope of greater than 0.25" per 12" run. The pipes size from the toilet should be at least a 3" pipe, perhaps bigger if the shower is joining it; a pipe of such duty should not run more than 6' to the soil stack.

  • + for mentioning cast not being forgiving. The rest sounds good also. – Ed Beal Feb 15 '18 at 22:18
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It sounds like you are in need of a new tile job for the tub surround.

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    Hi, Paul. One-line answers really don't convey enough information for a good response to a question, especially when there's another answer with a different opinion. Would you elaborate a bit? – Daniel Griscom Feb 15 '18 at 12:53
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If your shower head is right above your shower lever, check if there is a slow drip from the shower head down to the handle, after someone takes a shower. I had a similar problem in my last house, and luckily, my plumber noticed that when water dripped down the wall to the handle, it made its way behind the plate, and through the wall on downstairs. Remedied the situation by removing handle and resealing behind plate. Cheap fix. May not be what you are dealing with, but worth a try before you spend a bunch of money opening up walls.

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If you know for sure it’s your master shower u need to tear the ceiling under drain a small hole enough to see if that is true u can rent a hole camera to see in their not cause much damage also pour sugar free kool aid to actually see if it’s your drain or connection w out glue I had the same problem thought it was the shower but it was a rotten rubber on my vent pipe in the roof water was riding the pipes and coming off in ceiling

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there may be a 1/4" plastic tube that is attached to the shower assembly

it is meant to connect to a floor drain in a basement so that the floor drain trap does not dry up

maybe you have one of those and it has become plugged or disconnected

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