HELP! My downstairs 1/2 bath is right below my wash room. Recently I shut the water valve off in the bathroom to replace the vanity/sink in the bathroom. I have not cut the valves back on, but I noticed that when I run my washer a very small section of the wall in downstairs bathroom is moist/damp. Can someone please point me in the right direction?

Is it wet right inside the wall from your sink supply lines or elsewhere? By washroom are you meaning a laundry area with a machine? Could be a bad drain from the laundry or even a supply line. Back to you

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Originally Posted by ballengerb1

Is it wet right inside the wall from your sink supply lines or elsewhere? By washroom are you meaning a laundry area with a machine? Could be a bad drain from the laundry or even a supply line. back to you

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When I touch the wall, I can feel the damp spot so it appears to be from the inside the wall. The location is in the middle close to the right side of the wall. The room upstairs is the laudry area with machine. Does it have anything to do with me shutting off the water valve to the sink in the bathroom? If drain or supply line, how do I verify it is that or try to fix?

Is the wall made of drywall? If so you must open it anyway to replace the wet drywall. Once you open it you may better see where the water is coming from. I do not think this is caused by you closing the supply valve in the lower level, more like from the machine or its supply lines

Thanks for your reply. I will try that

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when I run my washer a very small section of the wall in downstairs bathroom is moist/damp.

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This gives me a clue. Hold off opening the wall until you answer. Do you have a washer stand pipe outside the wall or do you have a washer box?(see image) Back to you, Tom

Tom you are ahead of me with the leak fix but I think the drywall needs to come out no matter what. 24 hours after repeated wetness mold starts growing and the inside of this wall floor to ceiling has probably been wet on and off for many days. The leak probably is right at the top of that stand pipe so you finish the plumbing fix, then I'll help the guy with his drywall.