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Plumbing help: Need help troubleshooting shower leaking to ceiling below

  • Last Updated:
  • Mar 11th, 2019 11:52 am
Aug 25, 2006
206 posts

Plumbing help: Need help troubleshooting shower leaking to ceiling below

So I have a typical builder grade shower in a 15 year old home in GTA.

Floor is tiled so no acrylic pan or anything. Problem is it the shower is leaking to the ceiling below damaging the drywall underneath. I tore out the the appropriate section of drywall ceiling in the room below and found a crazy amount of soap scum/deposits around the shower drain assembly from below the subfloor. I chipped away all of the built up deposits (the white stuff on the black plumbing is the residue of after cleaning up as much as I could) to get to the point where I can view all of the plumbing. You can see the pic below. The water seems to be coming from the between the PVC liner and the subfloor somehow and not from any crack or joint failure in the black drain plumbing itself.


From what I can tell it is a typical drain assembly. I can clearly see the pvc shower liner and the drain body. The red part below is where the water seems to be seeping in from some how as the wood seems to be getting wet primarily with no obvious leak from the drain body itself or seam with the liner.:


For those of you in plumbing trade or who have dealt with this before what is least intrusive way to troubleshoot this with causing as little damage as possible? I'm not adverse to chipping away all the tile in shower floor and rebuilding it but I would like to avoid if at all possible if there is an easier way. The screw down strainer from the top seems to be seized and unrecoverable without the use of chisels and hack saw as FYI. All water damage and moisture is localized around the drain assemble itself so no issues with supply lines assumed.

I'm all ears. School me on fixing this please!
2 replies
Deal Addict
Jan 19, 2011
2858 posts
Clean it all perfectly, then run the shower until you start to see exactly where the drip is coming from.

In all likelihood, your repair will involve lifting and replacing the shower floor. You likely have a leak between the membrane and drain flange.
"The truth is incontrovertible, malice may attack it, ignorance may deride it, but in the end; there it is."
Just a guy who dabbles in lots of stuff learning along the way. I do have opinions, and readily share them!
Deal Addict
User avatar
Jan 2, 2012
3181 posts
There is no (permanent) way that I'm aware of, to repair this without ripping it all out.
Be prepared to remove the shower walls as well. As you can see from the drawing you posted, the waterproof membrane is continuous from wall to floor.

This type of construction has largely been abandoned since the mortar tile base is constantly wet, and requires drainage. The preferred method is having the waterproof membrane on top of the mortar base.