View Full Version : Sunday is "D(rain)-Day" -- and trap's offset is wrong.

11-21-2009, 10:00 PM
Well, the day I've simultaneously dreaded and anticipated has arrived (well, technically... I still have to go to bed and sleep before the big project in the afternoon). I'm stressing out badly, if only because this is one of the few tasks I can't do alone (at least, not without risking damage to the new tub), and tomorrow's the only day my friend can come over to help me until... well... about 2 weeks from now. So it has to be done tomorrow.

The biggest problem I'm seeing right now is the apparent fact that the old bathtub's P-trap is about 3 inches too far back. If you look at picture 1, you can see how I calculated it:

tub edge to back of overflow drain: ~5.75"
overflow drain, front to back: 2.25"
back of overflow drain to tub edge: 3.5"

subtracting .75" (half the 1.5" pipe") from 5.75" suggests that the new overflow drain's pipe is going to be approximately 5" back from the stud. The old pipe was apparently ~2.25" back from the stud.

Now, for the fun. As far as I can tell, I've removed everything from the old drain that can be nondestructively removed. It looks like everything from this point is going to involve cutting and gluing PVC.

The fun part, of course, is the fact that the two vertical pipe sections are both inside the ~8" diameter hole formed in the second floor's slab (the bottom of the hole is the top of the living room's drywall), so getting a saw in there won't be fun, and would probably require buying some expensive new tool(s). HOWEVER, replacing the entire P-trap won't be much more fun, because it only has about an inch before it disappears into the slab.

I should mention at this point that the bathroom is actually a slab cast on top of another slab. The builder formed the second floor's slab, then poured a second slab (delineated by the wood around the drain pit, and elsewhere around the bathroom's perimeter) with the drain pipes embedded inside. In a pinch, I could probably pry away the board the drainpipe passes through to get another half inch of pipe to work with, but for obvious reasons I'm nervous about cutting the pipe, because if I cut too much, the only way more pipe can be exposed is by breaking away concrete (at god knows what cost). The new 1x2 boards you see at the very top are coming off... I only needed THEM to dam off the area around the self-leveling concrete I poured yesterday.

So... any suggestions for which pipe to cut tomorrow after I've confirmed that the trap needs to be shifted 2-3 inches further from the wall? Is there any easy way to cut a "pipe in a pit"? Or is my only real option to cut away the entire trap, preserving as much of the pipe sticking out of the slab as possible? What's the absolute minimum length I can have before I'll have to pry away the old board used to form the second slab to expose enough for a proper glued joint?

By the same token, is there any good way to do the new trap in a way that will leave the door open to a third new drain, put in by me or whomever owns the house 25 years from now, without requiring slab breakage? Perhaps a PVC-to-[brass|galvanized steel|something-non-glued] fitting, so that going forward any new trap can be screwed on or compression-fitted instead of glued? That's my biggest objection to gluing a new trap into place... once the new trap is glued, there won't be enough exposed drainpipe left to ever cut THAT trap off and glue a new one to replace it.

Alternatively, are there any good ways to "cheat" and somehow use another section of pipe between the old trap and new drainpipe's bottom to shift it ~3"? God forbid, maybe a flexible pipe kind of like the ones they sell to make connecting sink drains easier?

Inspektor Ludwig
11-21-2009, 11:24 PM
If it were me, I would cut the pipe just above the u bend in the trap leaving as much pipe as possible coming down from the 90 sticking out of the wall. I would go get a new trap and trap adapter and a 1' piece of PVC (bring the cut out u bend and trap adapter with you). I would also get what's called a "mission coupling". It's a rubber coupling with metal band around it and use that as the coupling between the pipe coming down from the 90 and the u bend. It tightens with 2 hose clamps and will allow you to move the trap left or right without having to worry about being permanent but you'll need to add a piece of pvc to outlet side of the new trap so the coupling has something to grab onto. Before you glue anything together dry fit everything because you may need to trim the pipe coming down from the 90 so the bottom of the trap will fit.

11-22-2009, 04:45 AM
The way it looks is the tub sits on top of the 2x's above the concrete floor and the pit was formed just for the trap. To get the few more inches you can chip away at the concrete. It is really not that hard. Sometimes a cold chisel will do or with a concrete bit drill holes next to one another then chip away at it.

As far as the pipe is concern that is a bitch. You can cleanly cut the pipe right at the rim of the elbow to preserve as much pipe out of the floor as possible but here is the new problem. The pipe will be too short to glue on another elbow. The elbow will not reach the same spot in the pit. You cannot glue on a coupling becuase then it will extend to far over the pit to glue on a elbow. Using "street" elbows after the cut pipe might do the trick. Buy a bag of fitting and start playing around to see what might work. 45 degree couplings might work. I haven't looked it up but if 45 degree street elbows are available then that may work better for you.

The finale way is cut the pipe and use those rubber couplings, (as stated above) with the two stainless steel clamps to extend the pipe after the cut to get the fit you need.

11-22-2009, 06:44 AM
Well, if it were I, and I was REALLY concerned about that guy 25 years from now, I would "peel" that elbow off the pipe and start from there. BUT since I am not, I would cut the elbow off and not worry about the future.

11-22-2009, 07:28 AM
OK, just to sanity-check... does everyone agree that the only purpose of the wood lining the perimeter of the upper slab was forming the concrete, it was just left in place because there was no particular reason to go to the trouble of removing it, and that my best option is probably to cut off the trap (leaving as much straight pipe between the first elbow and where the straight pipe emerges from the slab as possible), then remove the board if necessary to expose more pipe?

As far as mission couplings go... I'm going to hit a few plumbing stores (I think there are a couple that are open until noon on Sunday). Are they really reliable enough to use in places that aren't easily accessible for future inspection? Or were they mainly designed for places that are semi-accessible, like basements and crawlspaces, so you can see if the connection is failing and fix it before it becomes a major problem? When you say "rubber", are they REALLY rubber, or are they actually some other material that won't crack, shrink, harden, etc over time?

Finally, is it safe to assume that Sharkbite-type couplings for 1.5" PVC pipe don't exist? ;-)

11-22-2009, 10:12 AM
This is the link to "Mission Rubber Products" Their stuff is pretty good and it may take 25 years to leak. as long their is no electric motor nearby (ozone generator).If this type of joint every leaked it would only drip straight down in that 8" pit and the water would show up on the ceiling below, This is what you want. The future owner will see a wet spot, open the ceiling and will be able to replace the joint and fix up the ceiling. A real easy fix.


11-22-2009, 10:38 AM
I prefer the metal shield couplings.

11-23-2009, 05:10 AM
Well, as luck has it, my friend fell through yesterday... but promised to come up and help me tonight (and tomorrow, if I'm right and it almost certainly won't be do-able in the hour or so I have after work before the neighbors bitch about noisy construction late at night).

I ended up buying a "Tyler Pipe Co" "no-hub" (ASTM C 565) B-70 B-602 1-1/2" coupling from a local plumbing store. From what I'm discovering, buying from "real" stores is kind of a dice roll... sometimes they have stuff that's a lot better than Home Depot/Lowes, other times it's equally mediocre or worse. Is it worth trying to spend my lunch today and/or tomorrow on a holy quest to find a genuine Mission CP-150 Band-Seal, or is the one I have good enough?

On a slightly different topic, what purpose do the ledger boards serve? Are they mainly to provide a uniform surface for screwing the tub flange to a piece of solid wood (instead of the steel flanges on the studs, which aren't very stiff individually)? Or do they serve some other purpose as well? Does their height matter, or does it only matter that some middle portion of the board overlaps with the nailing flange?

If I'm using screws instead of nails, what gauge screws should I use? Are #8 good enough, or do I need larger screws? Are self-drilling screws OK, or do I need to pre-drill the holes through the acrylic flange? Finally, am I correct that the nailing flanges themselves should rest against the studs... or at least the middle and plumbing-side flanges, with the third flange shimmed, and the ultimate backer board mounted to that third wall with equal shimming?

OK, a few more questions... I'm going to use Kerdi for the surround. Do I still need to use roof flashing over the tile flange, or does the Kerdi take its place? Or do I put the metal roof flashing over the flange, then put the Kerdi over the flashing?

The Self-leveling cement seems to have produced a nice, flat surface. However, I have a bag of Home Depot's cheapest tile mortar at my disposal anyway. Should I try to place some blobs so that they end up INSIDE the tub's hollow fiberglass bases, them trowel some more around the outside after getting the drain installed and the tub placed, just to anchor it better?

11-24-2009, 04:48 AM
Behold (pics below)...

the sweet smell of victory...

... and the agony of (temporary) defeat:

Actually, I don't think it's *quite* as bad as it looks in the second pic. I managed to get the wood (put there 25 years ago to act as formwork for the second layer of concrete below the bathroom) off in 5 minutes, but I won't be able to make another try at the tub until tomorrow night. The neighbors' master bedroom is separated from my bathroom by two reinforced-concrete walls that basically touch (from the outside, it looks like a party wall, but it's really two independent walls separated by a sheet of Tyvek). Normally, there's no sound transmission between our houses... but things that involve hammering and drilling the floor and/or wall *do* cause plenty of noise that's quite loud next door (I know, because my neighbors on the OTHER side scared me half to death a few months ago with drill noise when they were hanging new kitchen cabinets... the hammer drill just kind of resonated, and created this omnipresent vibrating howl that sounded like it was coming from everywhere at once)

11-29-2009, 07:37 PM
Epilogue: the new tub is (mostly) installed, and the drain is connected. I still need to shim and screw down the tile flange, but the drain appears to be watertight, and it looks like I put down enough mortar to make it both level and solidly creak-free.

The self-leveling cement definitely helped, because all I had to ultimately do to make it level was trace an outline of the tub's base with a marker, then glop enough mortar inside the lines to squish down and spread when the tub was placed on top of it, but not quite enough to squeeze out the edges and mess up the nice, level surface the hollow base's perimeter had to sit on.

One thing I *didn't* install were ledger boards, partly because the tub's (skimpy, generally inadequate) instructions didn't indicate what the normal deflection is supposed to be, but were explicit that the ledger boards must never, ever be loadbearing. If others here think it's important enough, I might try to find some suitable firm, but slightly-squishy foam padding at Lowe's or Home Depot tomorrow night after work, and try retrofitting some ledger boards under the edges. I actually *would* have done it tonight, but I ended up not having time to shop for the squishy foam supports before my friend showed up to help me, and today really *was* the last day he could come for a really, really long time, so it was now or (feeling-like) never.

Question: should I drill and screw the tile flanges through the shims to the studs with the tub full of water (like it is now), and maximally-depressed? Or should I drain it halfway or all the way before screwing the flanges in?

Also, what gauge bolts should I use?

If I have a 1x8 running along the entire side behind the flange, how far OC should the screws be?

11-30-2009, 04:23 PM
You are misunderstanding the intent of the ledger installation instructions!!!

You cannot 'hang' the tub from the ledger boards. They are installed in case someone sits on the edge to keep from breaking off the corner or cracking something. They prevent excessive deflection. If you don't install them, you'll have no warranty recourse when you break the thing. They ARE required in a proper installation.

11-30-2009, 05:05 PM
OK, no crisis... I can still get ledge supports under there. The thing is, though, at what deflection level do I want to immobilize the ledge and nailing flange? The point where it's maximally deflected downward (ie, full tub), the point where it's not deflected at all (empty tub), or somewhere in between? And how secure and immobilized to I want the nailing flange to be? Do I want it to be firm, but loose enough to wiggle a tiny bit if forced? Or do I want it to be so secure, the edge where the ledge becomes the nailing flange will crack before the screwed-in flange budges so much as a half-millimeter if the whole thing gets subjected to stress?


"Houston, I think we've, uh, got a problem..."

Last night when I did the initial test draining, I didn't see any evidence of leakage. Tonight, attempting to drain a completely full tub, I found a few, um, "issues"

1) It looks like the Mission Coupling is leaking.

2) I saw tiny bubbles in the joint of one of the couplings. I'm assuming they're leakage, and not just the way it dried (see pic).

3) For a few minutes, I thought I was going to have water coming *up* through the toilet's hole in the floor (flange?). Looking down into it, it kind of looked like high tide at the beach in Key West... water up against the seawall, occasional waves lapping up a little harder, but none coming up and over the "wall". The tub also drained *really* slowly. I think I've just discovered why the master bath's toilet used to clog all the time, and suspect the Champion 4 I bought to replace it isn't quite going to fix the problem. I tried using the ~6' drain cleaner I bought a few months ago, but no debris came out, so I suspect the problem is further "downstream".

I guess I should probably be thankful for #3, since I suspect the water backing up into the drainpipe and lingering in the coupling is probably why I saw the leakage NOW, as opposed to having it just drip a little tiny bit every day, invisibly nourishing a mold colony down there.

Sigh. I guess this means I'm going to have to re-do the whole trap, and try to figure out why the glued joint ended up (apparently) being non-watertight. I think I know what happened with the mission coupling, though... right now, it appears to be sitting only halfway on the pipe sticking out of the slab, whereas yesterday I had it basically flush with the slab. I'm not sure how it worked its way loose, though. As far as I can remember, I had everything completely screwed into place before placing the tub and attaching the overflow and drainpipes, so I'm not sure what apparently dislocated it.

By the way, how tight are the straps on the mission coupling supposed to be? I tightened them using a battery-powered electric drill, with the nut driver, on Torque == 1, and tightened them until it clicked.

11-30-2009, 06:44 PM
For the mission band, I believe the torque spec is 60 in-lb (5 ft-lb).

11-30-2009, 07:10 PM
You want the ledger board just touching the underside of the tub edge. If the whole tub deflects when filled with water, it isn't installed properly! You want the tub base to be solid, either by design, or added during the installation. As to screws or nails holding the flange, it's just to help position the tub initially. You don't want them really tight as you can get squeaks or stresses when the thing expands and contracts with temperature changes or the wood expanding or contracting with humdity changes over seasonal changes.

11-30-2009, 07:30 PM
^^ ah, ok. That's kind of what I suspected as far as the nailing flanges go.

As far as 60 in-lb goes, is there any straightforward way to figure out how far or close to that ideal I am without buying some really expensive tools to do it?

12-01-2009, 04:06 AM
Try Harbor Freight for a cheap torque wrench. If the adjusters were placed so the a socket wrench would be hoizontal to the floor, a 5lb weight on the end of a 12" long wrench would give 60 in-lb.

12-01-2009, 06:08 PM
Hmmm. I just had another idea at Home Depot.

Can I use a compression-nut fitting (like the ones used to join the overflow and tailpipe to the drain's Tee-fitting) to connect the P-trap to the drainpipe projecting from the slab in lieu of the mission coupling? Or is that [a bad idea | likely to be a code violation] ?

What I have in mind is to firmly attach the adapter to the drainpipe, then glue the trap together and glue it to the adapter. The general idea being that if I ever need to redo it someday, I can cut off the trap, then nondestructively unscrew the nut holding it on to the drainpipe.

Assuming it's not bad or illegal, would it likely be a better or worse solution than the mission coupling?

12-01-2009, 07:50 PM
^^^ Oops. Two new discoveries...

1. Contrary to what I believed an hour ago, the mission coupling did NOT slip and loosen during installation of the tub drain. It was, in fact, fully covering the drainpipe right up to the rubber separator in the middle.

2. The drainpipe coming from the slab won't actually FIT into the hole in the adapter's nut.

#2 was a disappointment, but #1 worries me. A lot. I apparently DID have both the drain's Tee and the drainpipe fully-inserted into the mission coupling, and I had both screws seemingly tight. Yet, it still leaked. It didn't gush or anything, but one week of daily baths, and the ceiling below would absolutely be damaged. Until I figure out why it was leaking, and how to reinstall it so it doesn't, I'm kind of at an impasse :-(

12-02-2009, 09:16 PM
Update: it looks like the problem was that I didn't tighten the bands on the coupling enough. Today after work, I bought a 60lb-in torque driver from Lowe's (~$10) and reassembled everything the way I had it on Sunday. This time, after filling the tub with about 20 gallons of water and draining it, I didn't see any water. Yay!

So, it looks like my next step is going to be getting the shower working & plastic temporarily hung so I can finally start living like a civilized person again. I have to admit, though, that it's going to be *at least* a week or two, and a few hundred-gallon+ drainings devoid of visible leakage, before I'm really going to start feeling like I can trust it and start making plans to build the new front panel to close it off.

For what it's worth, the torque driver tightened the bands *at least* 3-5 notches beyond what I dared to do on Sunday.

Note to anyone who sees this in the future and wants to buy a torque driver from Lowe's: they aren't in the tool department, and they aren't in the PLUMBING tool section... they're in a bin next to the union couplings. Handy, I guess, if you know you'll need one and are shopping for a coupling, but frustrating as hell to find if you're naive enough to think they'll actually be in the *tool* department. I actually had to look up the part number using my phone (Sprint Hero... Android rocks) so the employee could find them. He knew they had them somewhere, but was as stumped as I was about where exactly that might be.

12-04-2009, 06:43 PM
Update II -- the shower/tub mixer, head, and filler are all in place, and seem to be drip-free and watertight.

The anticlimax: seeing 4 streams of water coming from the filler that didn't really look like all that much water. Intellectually, I know it's the full capacity of 1/2" pipe and is probably the same amount the old tub used to deliver, and it's probably just an optical illusion caused by the fact that the NEW filler is so huge compared to the old one that it just "looks" like it should blast a firehose-like torrent of water... but still, it was kind of a disappointment.

The bad news: while filling the tub to test it (and blasting water directly at the top of the overflow drain due to my "too-short filler spout" problem), I noticed a tiny bit of dripping water. No gushing or anything, but there was a definite, visible trail leading from the bottom rear of the overflow drain's hole to the point where the tub's underside curved enough for it to slowly drip onto the floor. It looks like the basic problem is that the rear/underside of the tub isn't perfectly smooth... it's fiberglass, with tiny little ridges. It looks like the water is finding its way through one of them.

Any ideas what I can do to eliminate that? Right now, it's just PVC -> black foam ring -> hole in bathtub -> metal bracket with screw in the middle holding the whole thing together. I can't tighten it any more... the instructions said to only make it "hand tight, plus 1/4 turn". Do I maybe need to apply something to the rough fiberglass side of the tub to make it smooth so I'll get a better seal? Or should I just keep tightening it 1/4 turn at a time whenever I see a drip?