Shower drain leak from flexing

[Lost Dog]

The air in Southwest Washington had finally cleared and all was right with the world until I heard my wife ask "Why does the laundry room ceiling have a hole in it?".

In the bathroom upstairs we have a shower stall with a drain in the center.

(sorry, for some reason I could not get the images to show up in this post)

(I really need to scrub that down!!!)

Once I cut a hole in the drywall below I saw the issues seemed to be leaking from where the drain pipe meets the shower drain.

I put my phone in the hole and then ran the water and stepped around the drain. I was surprised to see the amount of flex from the shower. You can see the water coming out from between the drain and pipe when it moves up and down. The house was built in 1997 so it's had 23 years of flexing. I'm assuming this has a rubber gasket between the pipe and the drain and the flex has worn it down over time (small video in the link below).

https://imgur.com/0WICJuf

There is a large gap between the subfloor and the shower (about 1.5"). I shoved a USB borescope in there and got a picture. No mortar was used between the shower and the floor so it's just sitting on the wooden standoffs.

Two questions...

Is this just a case of unscrewing the old drain from below, pulling it out from the top and replacing it with a new one? I've heard it recommended to use either putty or silicon sealant between the drain and the shower floor. Either one better?

What can I do about the flex? It took ~20 years for this to be a problem but I'd like to prevent it again. Short of pulling the shower out and adding mortar, what can I do? I was thinking of shoving some wooden blocks in through the opening seen in the pictures above. If I could at least brace the center it may help. Any other thoughts? Hand pack some mortar around it from below? I've seen people suggest minimal expanding foam but I've also seen where people have lifted or cracked the tub / shower doing this!

I'm concerned that much flex is stressing the rest of the piping assembly below.

Sorry for the long post but I wanted to be thorough!

Thanks for all the help!!!!!!!

Neil

 

[Jadnashua]

You can see the beginnings of stress cracks occurring, which can lead to the actual pan leaking rather than just around the drain. Those fine cracks in the pan can make cleaning the top surface nearly impossible as they're below the surface and will stain and hold dirt - eventually, breaking through.

A new gasket might hold for awhile, but the same thing will eventually happen if you don't stabilize the pan. You do need to stabilize the bottom of the pan. IMHO, on a pan built like that, it's not an optional thing...it's mandatory to keep things intact long term. It won't be easy to put some mortar underneath around enough to support the pan properly. If you did try some door/window expanding foam, you might consider placing a sheet of thin ply in the pan, and then loading in some sand bags, or something similar to weigh it down while then injecting the foam.

Getting a new seal in there might be a pain...somewhat depends on if you want to replace the drain at the same time and the type.

Depending on how the drain pipe is supported, the movement of the pipe could, over time, cause a stress crack. Ideally, you'd be able to stop the movement when someone is in there.

 

[Sponsor]

 

[Lost Dog]

You can see the beginnings of stress cracks occurring, which can lead to the actual pan leaking rather than just around the drain. Those fine cracks in the pan can make cleaning the top surface nearly impossible as they're below the surface and will stain and hold dirt - eventually, breaking through.

Thank you for the reply! Where are you seeing the stress cracks?

A new gasket might hold for awhile, but the same thing will eventually happen if you don't stabilize the pan. You do need to stabilize the bottom of the pan. IMHO, on a pan built like that, it's not an optional thing...it's mandatory to keep things intact long term. It won't be easy to put some mortar underneath around enough to support the pan properly. If you did try some door/window expanding foam, you might consider placing a sheet of thin ply in the pan, and then loading in some sand bags, or something similar to weigh it down while then injecting the foam.

<sigh> It's amazing how many cut corners you find on a house. Everyone in my neighborhood has stories about thing they find going wrong with siding, window installs, etc. I'm actually paying off the house tomorrow! No wonder things are going wrong!!!

It seems like this is what I'd need to replace with:

https://www.oatey.com/products/oatey--140-series-101-pnc-plastic-nocalk-shower-drain-1402493307

Here's a look from right underneath:

This is looking down the pipe. The blurry part at the top is the P-trap. The black tube strapped tot he top is the line coming off the trap and that ties in to the lower drain pipe (that also has a tub drain behind that).

I think I have enough space and flex to use the Oatey I linked above. I can unscrew the old one, pull it up and then have room to remove the old nut and gaskets. Clean the pipe, slide the new nut and gaskets on then drop the drain in from the top. Screw it all together from the bottom. If I'm wrong on this, please let me know!

Then is the trick of reinforcing the pan. I REALLY don't want to replace this right now so I'd like to give it a go at stabilizing it. I've got some thin 1/8" veneer ply in the garage that would fit right in the bottom of the pan if the consensus here is minimal expanding foam being my best bet.

I'm thinking of rather than patching the ceiling I'll put an a click-fit access panel cover so I have time to make sure everything is good before I take the time to repair the drywall.

Thoughts?

 

[Jadnashua]

The discoloration of the pan tends to mean microcracks (stress produced cracking). Also, underneath, it appears that some fiberglass has shed from the bottom due to that movement. But, I'm not there to view it personally! When that gets really bad, the pan will literally just break. Think about an old steel coat hanger...you can bend it back and forth for awhile, but eventually, it will break...fiberglass has limits on how springy it is, and exceeding that causes it to start to crack. Limiting the amount the pan can flex should help extend its life, but it has (I think) already been damaged. I'd consider budgeting to replace the thing over the next few years...could last a long time, might not!

Should you decide to be interested in tiling a new shower, consider checking out www.johnbridge.com where their main focus is on tiling.

 

[Lost Dog]

The discoloration of the pan tends to mean microcracks (stress produced cracking). Also, underneath, it appears that some fiberglass has shed from the bottom due to that movement. But, I'm not there to view it personally! When that gets really bad, the pan will literally just break. Think about an old steel coat hanger...you can bend it back and forth for awhile, but eventually, it will break...fiberglass has limits on how springy it is, and exceeding that causes it to start to crack. Limiting the amount the pan can flex should help extend its life, but it has (I think) already been damaged. I'd consider budgeting to replace the thing over the next few years...could last a long time, might not!

Should you decide to be interested in tiling a new shower, consider checking out www.johnbridge.com where their main focus is on tiling.

Thanks much for the comments! I think the plan is to do what I can to reinforce it, replace the drain then in a few years (or sooner if catastrophic failure happens) do something new... Not sure if I put in another drop in shower or go with a tile. Plenty of time for the boss to tell me what she'd like!

If anyone else has comments or suggestions on reinforcement I'd love to hear it!

I have read a few suggestions on minimal expanding foam and as much as I don't like the idea it may be the best option in my case. The idea I liked the best was to shove some plastic garbage bags in there then fill in to the bags. This way it does not bond to the floor or bottom of the shower. Considering I'm a only a few years from replacing the whole thing I may as well minimize the headache for the demo in the future....

Then again, I screw this up and it will be done sooner rather than later!!!!!

 

[Reach4]

The idea I liked the best was to shove some plastic garbage bags in there then fill in to the bags. This way it does not bond to the floor or bottom of the shower.

I would be thinking sandwich bags etc, up to maybe quart size. Multiples, rather than one or two big bags. In each bag you would put a ball of mortar, bigger than the open space. For example, if the space was a 2 inch crack, you could shove in 3 inch diameter balls, each in a bag. A baseball is about 3 inches in diameter.

If the space were 1 inch, maybe golf ball size lumps.

 

[Lost Dog]

I would be thinking sandwich bags etc, up to maybe quart size. Multiples, rather than one or two big bags. In each bag you would put a ball of mortar, bigger than the open space. For example, if the space was a 2 inch crack, you could shove in 3 inch diameter balls, each in a bag. A baseball is about 3 inches in diameter.

If the space were 1 inch, maybe golf ball size lumps.

That's a good suggestion... There is about a 1.5" gap between the subfloor and bottom of the shower. It may take quite a few bags but I think I'm mostly needing to support the center foot or two around the drain. Much less messy (and more stable) than expando-foam.

What type of mortar would you recommend? I'm assuming to make it somewhat thick but not so much it does not squish and flow as needed?

 

[Jadnashua]

Some spray foam gets brittle once it cures and will crush and shatter. Some is more like a stiff sponge that has closed cells that is resilient and can provide some significant support and bounce back. I'm not sure using mortar stuffed in there will work that well...it might. It works when you can place it, then push the new pan into it, but getting a decent amount of contact area by pushing some in is a lot less precise. Some people use structo-lite https://www.lowes.com/pd/USG-50-5-lb-Bag-Foundation-Plaster/3099147.

You could make some donuts of plywood, cut in half so you can get it around the drain, and stack them. Foam them in place, maybe. If it's actually 1.5", 2x material could be used. Lots of choices depending on what you have available and how comfortable you are working with it.

 

[Reach4]

What type of mortar would you recommend?

https://www.quikrete.com/pdfs/mortarselectorguide.pdf

Not sure. I expect this is not critical, since the only load is compressive.

 

[Jadnashua]

If you go with a mortar, you could consider Quikcrete's sand topping mix. It's mostly sand with enough cement in it to hold it together. Mix it so it's more like wet beach sand...grab a handful and squeeze. If it holds together and doesn't drip, it's good. Put some plastic on the floor so the plywood doesn't suck too much water out of the mix. When cement cures, it literally incorporates the water into its chemical structure and any excess will evaporate. But, if you take too much moisture out, it won't fully cure. Too much water makes it weaker by holding the sparse cement particles apart from each other. Cement gains it strength by growing crystalline spikes that interlock, so holding them apart means less strength. The stuff will pack and not flow. It won't really make a bond with the fiberglass, at least not a strong one, so removal during the next remodel won't be an issue. Structo-lite will set up faster.

 

[Lost Dog]

Seriously.... Thank you everyone for the great discussion on this. If we ever cross paths I owe you all a beer.... All this talk of cement takes me back to my few Civ-E classes for my Materials Science degree.

This weekend I'm going to pick up a bag of quickcrete and play around to get the consistency. From there I'll figure out the best way to get it situated under the shower pan. If I can get the center of the shower stabilized it will make a huge difference from where I am now.

Feel free to make more comments if a bright idea show up... If not, I'll post something once I either fix it or fail in a spectacular fashion!