I had a water leak dripping under my shower onto the ceiling below. I replaced the drain (especially the rubber gasket), and now the leak seems to be much less.

It looks like the fiberglass making up the bottom of the shower pan is pourous and water is seeping into it. After shooting the water at the drain or clogging the drain and letting water build up a bit, the fiberglass around the drain appears wet from the bottom.

During my last test, no water actually leaked (dripped) at all, but the fiberglass appeared wet. Is this acceptable?


Pictures of the bottom of the shower pan:

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    You say shower but if the shower is actually a bath tub you take showers in, it could be the overflow drain cover is loose. And the drain could be fine and the leak could be from the supply lines. – Steve Wellens Jan 12 at 5:51
  • Thank you for inquiring. It's a shower, and the leak is not from the supply lines. – lmat - Reinstate Monica Jan 12 at 19:50

Even a small amount of moisture is not acceptable beneath your shower pan. If the drain is properly connected you shouldn't have any seepage. If you're still getting moisture you need to determine the source. You imply that the fiberglass pan may be porous. Fiberglass isn't porous so it shouldn't be seeping but it can crack. If it's a tile shower you could also be getting leakage around the seam between the shower base and the tile. Check and caulk all of the corners and seams.
You indicated the pan looked wet underneath. Looking wet doesn't mean it is wet but you need to find out. Just take a dry paper towel and wipe the bottom of the pan. If it's wet at all the paper towel will absorb any moisture. If you're still not sure, you can purchase a moisture sensor meter online or at a hardware store that will sense moisture levels in drywall, wood and other homebuilding materials.

  • (Edited my question to add pictures) You said fiberglass isn't porous, but I'm not sure why you think that. I mean, on the top where I stand, of course it's smooth and not porous, but the bottom is made of glued fibers, so of course it has gaps and voids. I understand that the glue and fibers aren't porous themselves, but I mean the whole surface with its voids, etc. has many places where water could seep. Do you see what I mean from my pictures? – lmat - Reinstate Monica Jan 12 at 21:44
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    In your pics I can only see a small portion of the shower pan around the drain - not enough to tell anything. I do see the subfloor which appears to be osb that is under the shower pan but it doesn't appear damp in the pics. When material is porous, such as osb it will permit water to permeate it. So if the osb is wet it means you have a leak somewhere in the shower or the drain assembly. A properly manufactured fibeglass shower pan is not porous but, again, it could be cracked. – HoneyDo Jan 13 at 0:24
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    I just looked at the pics again and, although the osb doesn't look wet I can see some very slight discoloration where it may have been wet at some point - but hard to tell. It may have been from the drain leak. You're the only one who can verify if there is currently moisture present - you have to be on-site. – HoneyDo Jan 13 at 0:33
  • Thank you for looking. The bottom of the shower pan is black, but closer to the drain, it's tan-colored (perhaps because of gunk from where it has been getting wet?). – lmat - Reinstate Monica Jan 13 at 1:06

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