Replace 42" tub w/48" tub?

Right now, I have a 72"x42" soaking tub that's going to be torn out & replaced with a new one. I'm thinking about replacing it with a 72x48" Laurel Mountain tub from Lowe's (assuming it's really available w/3-sided tile flange) because I have plenty of width available (54"+) and REALLY HATE the 23" "standing width" all the current 72x42 tubs w/ledge & tile flange seem to have.

If I get the 48" tub, what kind of problems & expenses am I likely to encounter above & beyond those I'd likely have anyway? For example, the drain... the 48" tub's will be 3" to the right of the current tub's, and I assume I'll have to shift the shower/faucet/filler 3" right, too. The room will be stripped to the bare concrete & studs, but breaking the floor slab is out of the question.

Put another way, am I looking at 2 cuts to the water lines & two 3" extensions, plus a slightly angled drainpipe vs one totally perpendicular to the wall, or am I looking at catastrophically expensive modifications to the plumbing to accommodate the 6" wider tub?

tub

Where is the drain on YOUR tub and where is it in the new tub. Usually the drain on a tub with tile flanges is in the center so they do not have to make a left hand and a right hand drain model.

hj said:

Where is the drain on YOUR tub and where is it in the new tub. Usually the drain on a tub with tile flanges is in the center so they do not have to make a left hand and a right hand drain model.

Click to expand...

Both drains are right-side (facing the tub alcove). But, since you mention it, would installing a tub with center drain be a simple matter of buying approx 6 feet of drainpipe & a couple of bends to route around the tub's perimeter to the original drain's connection point, or would it mean breaking into the slab?

You typically don't have enough height to run the drain under the existing tub. Ideally, you want the drain right near the trap. Why can't you break a little slab? Except in certain circumstances (post-tensioned slab, for example), it isn't really that big a deal.

Actually, it's NOT slab on grade. It's a cast in place reinforced concrete two-way "slab with beams" (in this case, the beams are cast above the perimeter walls and rest upon them) that's 6" thick (12" in the bathroom) and sitting on a corrugated steel pan deck. I doubt it's post-tensioned, but it honestly wouldn't surprise me if it were. Anyway, that's why I basically view the slab as holy, sacred, and inviolate... even if it CAN be modified, I'm pretty sure even the most trivial change would end up being prohibitively expensive (god knows, I'd love to have a cylindrical skylight or two in the bathroom too, but I shudder to think how much it would cost to get a 18" hole bored through the roof seeing how I was quoted $600 to cut a door through the rear wall for a cat door).

Before you ask, it's legally a single-family home, but looks like a townhouse, and is built like a mid-rise office tower. The builder exploited a loophole in the zoning law that allowed him to build single-family homes at higher density than townhomes. It never occurred to the city commissioners that you could skirt the definition of "townhouse" by making the roofs concrete instead of wood separated by a concrete party wall, and building structurally-independent houses side by side, separated literally by a sheet of Tyvek.

But anyway, back to the problem at hand... I was told by a guy working at a plumbing supply store that bathtub drains don't actually go straight down, even if they ultimately go down into the slab. He said they all travel horizontally (above the slab) for some distance, even if they DO ultimately end up going down through the slab. If that's the case, it seems like buying a new tub with drain that's 3" further to the right than the old tub (48" - 42" = 6", 6" / 2 = 3") would almost be a non-issue lost in the background noise since even a new 42" tub is likely to end up having its drain in a slightly different position. Is that true? I've bought 4 books on plumbing so far, but they all seem to either avoid the issue, or were written by people who think all homes are wood and have basements.

OK, boiling it down to the essence:

Baseline: new 42" tub to replace old 42" tub in 3-sided cove. The new tub's drain, like the old tub's, is a right-side drain that's the same distance from the rear alcove wall, but probably differs in its offset from the right wall (where the showerhead and plumbing lies) by 1-4".

Alternate scenario #1: new 48" tub with same right-side drain orientation. The drain is 3" further from the alcove's rear wall (and by extension, shifted to the right by 3" relative to the 42" scenario if you were standing in the tub facing the wall with the showerhead), and probably more or less the same distance from the wall with the plumbing as the tub in the baseline scenario. Is this likely to be a lot harder/impossible to deal with than the baseline scenario if breaking the slab is out of the question?

Alternate scenario #2: new 42 or 48" tub whose drain is centered between the right and left alcove walls, near either the rear alcove wall or the opposite side of the tub. To get to the original drain trap, at least 4 feet of pipe running alongside the tub above the slab would be necessary. Can this be done, or does my inability to cut into the slab rule out this scenario?

Thanks!

I just had an idea, and need to know whether it's ridiculous, worth investigating, or likely to be a do-able DIY project.

Pretend you're standing a few feet away from the tub alcove, looking into it. The tub's drain is on the right. On the other side of the alcove's left wall is a closet accessible from the hallway. Suppose I were to sacrifice a foot of the tub & the entire 2x4 hall closet, and used the space for a walk-in shower 3 feet wide x 4 feet deep, separated from the new 5' tub's foot by a frameless glass panel (with everything in between waterproofed with Kerdi).

Now, here's the catch: remember, the slab is untouchable, and the only drainpipe anywhere nearby is the one the tub is using. If the new shower's drain had to achieve its entire downward slope by raising the receptor base high enough to do it, and the total distance between the shower's drain and tub's drain were ~9 feet (~2 feet diagonally to the corner where the shower meets the tub, a 45-degree turn, 5 feet alongside the tub's base, a 90-degree turn, then a final 16-inch run to the vertical pipe into which the tub (new and old) drains...

* does this sound like a reasonable, sane alternative worth considering? Or does the fact that the new shower's ten foot (give or take) drain pipe would have to run entirely above the surface of the subfloor slab make the whole thing too kludgy to consider?

* approximately how high would the receptor have to be raised above the slab (compared to the height it would have to be if it replaced the tub entirely and sat on a retrofit base with drain in the usual "tub" position)?

Thanks!!!

(I'll have to wait until I get home to list the plumbing books, sorry)

Each fixture needs its own trap and vent. Plus, the tub is probably 1.5" drain (although it could be a 2" pipe), and the shower needs to be 2" all the way.