Shower - What is going on here?

[BrianZ06]

Hi all,

We recently purchased the house. Its about 100 years old. I would guess the master bathroom was redone 25 years ago, but dont know for sure. The master bathroom is on the 2nd floor. While pulling some hair from the shower drain, I noticed that the drain looks like a potential catastrophe of some sort in the making. The shower floor tile seems to be set on some sort of concrete base. The top of the drain screen piece is flush with the tile and is screwed down. But there is a gap between that piece and the pvc pipe, allowing the water to eat away at the exposed concrete, seemingly digging a big gap between the drain top piece and where the pvc pipe starts. The concrete sediment then seems to have coated the inside of the pvc pipe turning it into a mess.

I'm guessing there's not much to do, but redo the entire shower base and drain plumbing. Why would anyone design it like this? Why wouldnt the pvc pipe meet the other piece? Maybe someone just mismeasured the pvc pipe. Any other thoughts for potential fixes or ways to delay the ineviteble?

Thanks!

Brian

 

[Tuttles Revenge]

There are generally 3 main parts to a mudset shower drain. There is the body which connects to the p-trap and sits on the subfloor. Then there is a clamping ring which clamps a waterproof membrane between the two. The third part is the adjustable top which has the strainer on top. What you may be seeing is a void below the adjustable top which is a bit of a Bell created in the body.

 

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[BrianZ06]

Thanks, much appreciated. So, in theory, the white PVC pipe I am seeing is watertight with the waterproof membrane (which should cover the whole shower base)? So, while water might continue degrade the mortar (potentially clogging the drain), it shouldn't be able to reach the subfloor - is that a fair assessment?

Thanks,

Brian

 

[Tuttles Revenge]

That is the general idea yes. Everything breaks down over time, but the better materials and better intallation prolongs their life.

 

[Jadnashua]

Those accumulations could be mastic rather than cement based products breaking down. Cement can break down from acids eating some of it away...when that happens, it dissolves and what's left is the sand that's part of the typical cement-based thinset. A tell would be to scrape a little off and see if it is more like a hard putty, or more like stone. If really hard, the final test would be to place it in a glass bowl, cover it will some simple vinegar, and let it sit for a day or two. If it's mineral deposits, it will dissolve. If it's a mastic, it will just get softer. A mastic is not suitable for use on the pan of a shower, especially those from 25-years ago. Some of them are suitable for use on the walls there, but other than convenience, they cost lots more than a decent cement-based thinset. FWIW, thinset is often thought of as being a cement based product, but in reality, it is a method and could be a mastic, or a cement-based material. Neither the tile nor grout is considered the waterproofing in a shower...it's the liner. The tile and grout are a decorative, wear surface, not waterproofing. A conventional shower pan construction generally stays slightly damp beneath the tile. That will give a mastic problems. It should have no effect on cement-based products unless your water or cleaning products are acidic.

I can't tell from the picture, but that drain looks more like a floor drain than a clamping drain typically used in a tiled shower base.