Waterproofing freestanding clawfoot tub in shower pan/wet box [Archive] - Ceramic Tile Advice Forums - John Bridge Ceramic Tile

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mule169
12-26-2016, 01:36 PM
Hi all,

I've been lurking here for awhile after I had an offer on a house accepted. Great bit of reno needed. I'd describe myself as a highly competent DIYer but I'm stumped on a question for the small bathroom project I'm going to be doing in my new house.

The house came with a great clawfoot tub, that is in amazing shape. A small bit of refurb and It'll be an awesome piece in this small bathroom. I'm planning on installing the clawfoot tub "inside" the shower box that I'm going to be building. It's a small bathroom, and despite all the threads that say "just get a shower curtain setup I'd much rather have a full shower pan with shower, and the tub available to soak in when not showering.

Much like this but with a frameless glass panel between the business side of the shower and the vanity (note the floor drain under tub, and the tub drain going through the shower floor)
191455

I'll be pouring a mortar bed for the shower, and using a 2" square drain much like a lot of typical shower projects.

So on to my question that after MUCH scouring the interwebs I haven't been able to find a good answer to. What's the best method to waterproof the clawfoot tub drain as it's going to have to punch through the waterproofed shower pan? Some of the suggestions and questions I've seen and mused about:


Install the shower drain and tub drain on opposite ends of the shower and don't worry about it. You'll tile around the drain pipe and the sealed tile/grout will do a good enough job of keeping water from seeping down the tub drain. - Obviously, I'm not fond of this

Use one of the OS&B drains, or one of those F2 drains for the tub. - The problem I see here is that it's installed in the sub-floor at the rough in. It looks like it's more suited to installations where the tub is sealed around the bottom to minimize water from flowing in? I suppose I could waterproof the subfloor around the drain pour the mortar bed around that, and then try to waterproof around the drain pipe before/after tiling. Just try and overkill the heck out of it. There are no weep holes in those type of subfloor drains though and I'm afraid that if water gets down there it's just going to pool.

Install a second shower drain in the shower pan, or plumb the tub drain into the main shower drain and just let the tub water open air style into the shower drain system - I've heard folks say this won't work as the flow rate from a tub is much higher than a shower (Still have yet to have anyone explain to me the fluid dynamics of why tub drains are usually 1 1/2" and a 2" shower drain wouldn't be able to cope with the flow rate :idea: but I'm guessing it has to do with the tub drain being sealed and the shower drain being "open to the air")


Any advice or experience folks could provide me with? I'd be happy to pay one of the professionals on this forum for the knowledge of a method that they use or that has worked well.

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jadnashua
12-26-2016, 03:53 PM
Your shower has typically, a 1/2" line coming to it and a showerhead is limited to 2.5gpm maximum...you might have 50g in a tub like that, and it might drain in 2-3 minutes. Say 2-minutes...that's 25gpm...LOTS different than a shower! Now, if you didn't care about how fast the tub drained, you could put in a restrictor (a reducer) on the outlet, and it might not overwhelm the drain. The issue is not so much the actual drain itself, but the 1/4"/foot slope of the shower pan.

If the outlet of the tub was right above the shower drain, most of the flow would go directly down the drain, and a 2" shower drain line can handle the tub outlet, at least with most grate designs.

You might be able to modify the grate so that the tub drain went into the funnel of the shower drain, and there would probably still be some grate openings to allow water from the floor to drain as well if there was an overflow, or say you mopped the floor.

mule169
12-27-2016, 10:54 AM
Thanks for the reply @jadnashua!

Your shower has typically, a 1/2" line coming to it and a showerhead is limited to 2.5gpm maximum...you might have 50g in a tub like that, and it might drain in 2-3 minutes. Say 2-minutes...that's 25gpm...LOTS different than a shower!

Totally get the flow rate of a draining tub is much higher than that of a shower head, I guess my "fluid dynamics" question was more a question of why if tub drains are generally 1 1/2", why you couldn't just do as you've mentioned above and dump the tub outlet down the 2" shower drain?

I've seen posts where this is frowned upon, but no real reason was given :shrug:

I'm still leaning toward putting a dedicated tub drain through the shower pan similar to the pic in my OP, but haven't found a great description of how to waterproof that type of setup.

Any insight would be super appreciated!

jadnashua
12-27-2016, 11:30 AM
I think that you'd find the typical slope of a shower floor would be the limiting factor unless the tub's outlet was directed into the drain itself, rather than having to flow across the floor to get there. The water will want to spread out across the floor because of the force. The head from the tub creates about 0.43#/foot. Once water is on the floor itself, at 1/4"/foot slope, the head is minimal, but enough to make it all work.

If you could move the shower/floor drain to directly underneath the tub's outlet, especially if you can modify the grate so that it wouldn't back up on the restrictions, it should work.

You could put a second drain in, but which one would depend on the type of waterproofing you choose. If using a conventional liner, you'd need a clamping drain. If using a surface applied sheet membrane, a bonded membrane drain. A linear drain could work and be the only drain, but they're pricey.

mule169
12-27-2016, 11:57 AM
Thanks again for the reply jadnashua.

I get where you were going now. Yeah, I wasn't planning on letting the tub drain into the shower and flow down the floor to the shower drain (my bad for not being clear in my first post). The suggestion that was made to me was much like yours. Install the shower drain at the same end as the tub outlet and plumb the tub outlet "through the shower drain strainer" more or less directly into the shower drain.

My current plan is to do PVC liner, mortar bed, roll on waterproofing membrane (Redguard, Latricrete or the like), tile in that order. I'd planned on using one of the "clamping" style drains for the shower drain.

For the tub outlet/drain I'd like to just run the outlet through the shower pan, and not have to install a second "shower style" clamping drain and monkey something together to route the tub outlet down through that drain.

I'd like to do something like you see in the image from my original post. I just haven't seen anyone really document a solid way to waterproof a setup like that where the tub outlet goes straight down through the shower bed.

jadnashua
12-28-2016, 11:15 AM
There are really only two ways to ensure the floor is waterproof...use a clamping drain in the liner, or use a surface waterproofing membrane bonded flange drain.

FWIW, painted on waterproofing over the setting layer with a conventional liner is NOT a great idea. In this case, two waterproofing layers is not an improvement...doing one of them properly is far better and more reliable.

If you got a large enough flange, you could cover the opening of a typical shower drain. Or just use a holesaw to make a clearance hole, so the edges of the grate show, and put a flange on the drain pipe that will cover most. Drain grates are available in both round and square...in this case, a round one might be neater, but then that makes cutting the tile a bit tougher around it.

mule169
12-28-2016, 12:32 PM
FWIW, painted on waterproofing over the setting layer with a conventional liner is NOT a great idea. In this case, two waterproofing layers is not an improvement...doing one of them properly is far better and more reliable.

Curious why this is? Just because of the potential for water to be trapped between the two membranes? I'd planned on using cement board on the walls of the shower and using a roll on waterproof membrane in the whole shower. Down the walls, onto the pan, and up to the clamp drains. Figured PVC barrier under mortar and waterproofing on top/walls would be a pretty bullet proof way to go.

If you got a large enough flange, you could cover the opening of a typical shower drain. Or just use a holesaw to make a clearance hole, so the edges of the grate show, and put a flange on the drain pipe that will cover most. Drain grates are available in both round and square...in this case, a round one might be neater, but then that makes cutting the tile a bit tougher around it.

Good advice, I had kind of resigned to doing this sort of setup. I'd thought of maybe just cutting a normal circular clamp style drain grate down. So basically cut off the "top of the funnel" to make the diameter of the grate closer to 2" than the typical 4" you see on most of those clamp style drains. This would make it easier to find a flange that I could slide over the tub outlet and slide down to cover the drain grate.

Probably the most idiot proof way in any case given that clamp style drains are standard, easy to install, and probably easy to pass inspection.

Thanks again for the responses.