Tub leak from below (?) How is my bathtub supported (1966 cast iron)

[AcidWater]

Trying to find source of leak. Leaks when showering. Guessing its rusted or cracked in the integral drain. Does that ever happen? When it dries I will test by running water into the drain without using the shower hose.

Not seeing loose grout or caulking -- the bezels on the faucet handles are not sealed, but they don't get sprayed continuously. A while back I had to re-grout the soap dish/grab handle, it was leaking a lot more from that gap. I will caulk the bezels.

There is a hole in the plywood flooring on the near side of the drain piping, I can stick a mirror & light in to look around a little bit. The top of the flooring is wet & it spreads to certain areas, then drips down in certain places.

Tub overflow line feels dry, & would not be a continous source of water.

I cannot see the shower riser. Its copper, could have a pinhole. But cannot confirm water flows from there along the top of the sheathing.

Cannot see the valve set either. 3 valve type, 1966. Could have erosion leak ???

I can see & feel wetness UNDER the tub

The cold water riser goes up on the far side of the center joist & the sheathing at the hole is wet -- but that would give a continuous leak problem, not just when using the tub. Could be flowing there from elsewhere.

The gasketed drain area is partly over a joist & sheathing. It rests on the sheathing -- should the center (keel) of the tub make contact? Or only the outside edges of the tub? What are the load bearing areas?

The portion of the bowl which I can see is half an inch above the flooring, but cannot see the central "keel" area.

I want to cut away the sheathing at ccccc and around cw so I can see more of the drain & maybe under the tub on that side. But its narrow, the distance between joist & stairs, & I have to reach sideways.

O = drain at gasket as visible from below. Actually larger diameter.
0 = short horizontal run - is this cast into the tub ? I can't see it.
D = drain opening as seen from top of tub.
o = horizontal drain pipe.

| = seam between two sheets of plywood. Seeps thru here but not the main leak point.

.... = plywood sheathing/flooring.

cw = cold water supply riser.

222 = 2x4 on edge between joists, above plywood. Seems to be there to support the hot water line. Or to prevent joist from twisting due to load?

2h2 = point where hot water supply rises upwards thru it. Not wet above, but major leak is thru hole. Must be horizontal gravity flow towards it. Only drips when running tub water, so its not a pinhole in the pipe.

hhhh = horizontal run of hot water line. This and the ooo drain line are somewhat above each other, so dripping water can run along it or both; the area LLL edge of sheathing at the cutaway area might also be where its coming down from.

TOP VIEW:
bottom / basement stairs / top
....................................|
....................................|
........cw........................|
xxxxxxxxxxxxxxxxxxxx FAR SIDE
xxxxxxxxxxxxxxxxxxxx
......................................................
................cccccc...........................
xxxxxxxx.cccccc.xxxxxxxxxxxxxxxx
.....222 O0D LLLLLL
.....2h2 oooooooooo-->>
.....222hhhhhhhhhhhhh -->>
.....222
xxxxxxxxxxxxxxxxxxxx NEAR SIDE

The far side is a double joist -- but its also got the basement stairs on the other side so I don't know if the double joist is to bear the load of the tub or just the way the stairs were built. Both bathtubs are "in line" so the two tubs are above the same joists.

There is a single joist just beyond the near edge of the tub (the vertical edge, not the "bowl").

 

[Jadnashua]

Lots of questions!

The tub/shower area should be water tight without the tile or grout or caulk, but many are not installed per the industry standards.

Most CI tubs have feet that it sits on, and are designed to have the long edge also up against a ledger board. Because the subflooring is often not perfectly level, they'll either put shims under the feet, or bed the thing in mortar.

Older installs may have used plain drywall or moisture resistant drywall on the walls. That is not allowed today because we've learned, it doesn't work. Neither the tile nor grout is waterproofing...they are decorative, wear surfaces. So, what's behind them needs to be able to get damp. To keep the studs from rotting out, the standards call for either a surface applied waterproofing on the front (and sealing to the tub surface), or a moisture barrier (plastic sheeting or roofing felt) behind the wall board and lapping over the tiling flange or lip, and today, the wall board would typically be a cement board (cbu).

If the tub is not leveled, water will tend to pool when you take a shower on the top rim, and can flow. It can get high enough to get over the tiling flange, which on a CI tub is often just a slightly raised lip.

Yes, it could be from a pipe with a pinhole, or the fitting where the shower arm attaches may have split (or it could be they used a galvanized one, and it is rusting out). Do you get a shot of rusty water when you first start out?

FWIW, if you have a 3-handle shower control, the thing is pretty old. If you do find the source of the leak, and it's an easy fix, you're lucky. It might be time to start to save up for a remodel to spiff things up a bit and bring the install up to modern codes (and probably styling).

The things I'd start with are:
- see if the tub is actually level in both directions (on the rim - in/out and L/R).
- get a cap for the shower arm, turn the water on for the shower and wait to see if you get any leaking evident

If neither of those point to a problem, you can try caulking all over, but that will just be a bandaid...the real solution will be a remodel. If the tub is in good condition, you can keep it, but I'd put in a new tub/shower valve and redo the walls and tile. Of course, that often leads to much more work, and if things are rotten behind the tile, it can escalate quickly.

 

[Sponsor]

 

[AcidWater]

> the fitting where the shower arm attaches may have split (or it could be they used a galvanized one, and it is rusting out). Do you get a shot of rusty water when you first start out?
>
No rusty water. But now I want to try to unscrew the shower arm & take a look behind the trim ring...

How does one replace a shower riser pipe without a huge vertical gash in the wall? That would mean also replacing the 3 valve set with a modern one, so a big hole on the bottom with a cover plate. Cut off the old riser, it can stay behind the wall. Then use a flexible pipe, dropped down thru the arm hole? But then how do you support the shower arm up at the top end? Are there plates to screw into the wallboard?

Frustrating that FINDING the leak seems to involve destroying something, maybe to find the leak is not behind that part.

 

[Jadnashua]

If the wet wall is an interior wall, it may mean tearing up the wall behind the tub, not FROM the tub side. If you're lucky, it's in a closet so you don't have to be as neat when you put things back together again.

Most of the valve manufacturers make a remodel plate to cover the larger hole needed to install an anti-scald valve. If the riser is intact, you'd reuse that. IF not, and you can't get it from the back side, then, yes, it's tearout time. Since the tile will almost certainly not still be available (unless you're really lucky, and there's a bunch of spares around maybe in the basement), by the time you've done that, it may mean it's time to tear it out and remodel the whole tub surround. If the pipes are galvanized, it's time to consider a tearout and replace that as well.

 

[AcidWater]

I guess you could also insert short lengths of cpvc and glue them together.
I ran the hot water thru the shower into a bucket & now its wet under there so looks like I need to open up the tiles & replace the valve set & riser.

 

[Jadnashua]

It's easier if you can access it from behind rather than in front. You do need to anchor the drop ear el for the shower arm, and that isn't done easily without some access, but as to the valve itself, you should be able to deal with that from the properly sized hole as called for in the renovation/remodel plates offered by most manufacturers. Here's one from Delta. It comes in various finishes. There are others that are different shapes.

 

[AcidWater]

The other side is the other bathroom, so ruining my tiles either way.
How is the riser generally anchored ? Do they strap it to a horizontal 2x4? Hopefully not with a hole THRU a 2x4.
Am I going to need a plumber, a drywall guy, and a tile man, or can the plumber do it all?

 

[Jadnashua]

While you can strap the fitting at the shower arm, the better way to do that is a drop ear el...a fitting that has screw holes, and that is anchored to blocking. This makes the shower arm nice and stable, and lets you screw it in without torquing things and maybe stressing a joint.

While there are plumbers that may be great tile people, I wouldn't count on it. FWIW, drywall behind tile in a wet area hasn't been the industry standard for decades, but people still do it sometimes. Neither tile nor grout are waterproof, so drywall tends to disintegrate, depending on how much spray gets to the wall. Opening up the wall more than a remodel plate will cover, may mean your better choice is tear out the surround and refresh it with new all around. If I were going to do that, I'd use something like KerdiBoard. Here's a video of the process..https://www.schluter.com/schluter-us/en_US/video_kerdi-board#10

You may not need to do anything to the shower head riser until you determine where your leak is. If it's from the valve, just replace the valve unless the pipes are galvanized...then, it's prudent to replace it all.

 

[AcidWater]

I have heard of Kerdi board. But the thing is that I've already had to replace all my copper cold pipes due to pinholes caused by acidic well water. So replacing the copper riser seems prudent. If there is a galvanized drop ear up at the top, that probably is also subject to corrosion from the acid.

So maybe I should open it up so I can see exactly where the water is coming from, then decide whether to risk the riser. However, I might be able to rig up a catch basin below it with a gravity drain tube going to where I can see it.

I need to know how to make a correct sized hole for a new valve set -- is there a standard template, or a choice of larger sizes? Gotta be able to get your hands in there to work. With instructions I could make the hole before deciding exactly what to do & calling the plumber.

I like Price-Pfister. I suppose I should buy what I want because plumbers don't carry everything ?

 

[AcidWater]

What trade does the wall -- should any plasterer/gypsum wallboard tradesman be able to do it & make it waterproof?
I'd rather tear up only the one wall -- how do you get a waterproof join at the corner?

 

[Jadnashua]

Most tub/shower surrounds that are tiled are not waterproof.

The walls are typically cement board (cbu) with a barrier behind it (plastic sheeting or roofing felt). The joints are covered with an alkali resistant mesh tape and thinset mortar. While not waterproof, the walls are not damaged by becoming damp. Typically, any moisture that gets behind the tile isn't much, and it evaporates out the front. The moisture barrier behind is to protect the studs from seeing any moisture that might result from things becoming more damp than 'normal'.

If you build a wall out of say KerdiBoard, then you can make the entire wall waterproof.

There are numerous paint-on surface waterproofing materials you can use to waterproof the inside of cbu. RedGard, Aquatech (sp?), HydroBan, etc. are all similar materials. For one wall, though, you'd be throwing away most of the bucket, and the stuff isn't exactly cheap. You'd need to follow their instructions on how to seal the material to the tub surface.

Without tearing out a row of tile on the long wall, you wouldn't be able t0 make a good seal there. You could try just putting a bead of silicon to join the new wall to the old. FWIW, industry standards call for all changes of plane or material to be caulked, not grouted when installing tile.

If you go with a remodel plate, they come with a template that shows the size and placement of the hole needed. If you have a bisque tile, a series of holes from a carbide drill bit would let you knock out the required hole pretty quickly. If it's a hard porcelain, it becomes a lot harder, and you'd generally need diamond tools to cut the tile successfully.

 

[AcidWater]

"The joints are covered with an alkali resistant mesh tape and thinset mortar." -- from the backside or laid upon the tub side?
And then a line of caulk down the seam on the tub side ?

"remodel plate, they come with a template that shows the size and placement of the hole" -- yes but I'd like to be able to cut my hole before buying the valve set, so I can figure out what exactly I'm going to need for the job. Are these plates custom to the valve set, or just various sizes with two holes in the center for the single valve & spout?

bisque v porcelain -- how do you tell the difference? What's bisque? This is 1966...

 

[Jadnashua]

The mesh tape is designed to bond the cbu panels together to act like a monolithic structure and is done from the front. Note, if you're not going to apply a topical waterproofing, you can add that when you start tiling rather than doing it previously...that helps to prevent 'speed bumps' from accumulation of thinset in the corners. Typically, in the corners then, you wouldn't use any sealing caulk. If you were to choose to use a liquid waterproofing application, you'd need to tape and thinset the seams and let that cure before that application.

At the wall/tub junction, you'd only caulk that.

If you were to choose something like Kerdiboard, or a topical sheet waterproofing, you'd seal the board or membrane to the tub with sealant. A liquid applied waterproofing, depending on the brand, might call for tape covered with their waterproofing, depending on the gap size.

 

[AcidWater]

Good thing we have two bathtubs... decided to call a general contractor & he can get all 3 trades if needed. & there is other work to do around the house that I just cannot do right now. Just not a great time to be spending megabucks.