Questions on replacing Shower with Tub

orourkeJune 20, 2009

I am redoing one of my bathrooms (walls & plumbing).

I would also like to replace the old (1958 era?) corner (32"x32) fibergalss shower stall with a bathtub-shower combo. I have 63.5" between the studs. My questions are:

I assume I should be able to fit in a 60" tub. Or am I wrong?

Will it be possible to get that tub through the 27" bathroom door?

I also assume that I will have to cut the old shower stall into pieces to get it out the door.

Most likely, I will have to move the drain. Do I have to also move the P trap? What about the drain pipe vent? How far can I move the drain without having to also move the vent?

Any advice appreciated.


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Yes, it can be done, and it sounds like there's room (turn the tub on it's side to get it through the door). Moving the p-trap is part of moving the drain, so "yes" to that. The vent will still be close enough - no worries there.

But if you're not experienced with this type of project, don't go it alone. Too many ways to cause major headaches, water damage, etc. I would at least have the drainwork and setting the tub done by a pro.

    Bookmark   June 20, 2009 at 2:11PM
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If you are installing a skirted tub that has no access panel through an adjacent wall or up from underneath you will be required to install a permanent "glue-in" type P-trap.

The shower should have had a 2" drain line, while a tub only requires a 1-1/2" drain line, however there is an exception in the codes which allows increasing the size of a drain line by one nominal trade size, so the 2" line will be fine.

    Bookmark   June 20, 2009 at 4:45PM
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Thanks for the advice.

I ripped out the walls, flooring and old shower stall. I had to cut the shower stall (used jigsaw) to get it out.

The current drain line is indeed 2". But I am also planning to redo the shower and sink drains (I will post another thread about this). I will redo them because although there is no leak, they are a mess going from ABS to cast iron back to ABS and then back to cast iron before joining the 4" toilet drain. Many flexible rubber joints, including a rubber Y to be used as a cleanout So I will choose a good spot to cut the cast iron, preferably close to the 4" Y and redo everything in ABS.

Access is not a problem since I am on a perimeter foundation with crawlspace.
I actually opened a hole on the floor between two joists so that I have a second, quick access to the plumbing, rather than having to crawl 40Â through the normal crawlspace trap door. Seems like I may have to do some structural work under there anyway to repair water damage from an old roof leak (before I bought the house), but that is another challenge for the structural forum.

So, nowÂ

another plumbing question is how far from its current vent can I move the tub without having to also relocate the vent? Because, if I, say, wanted to move the drain on the opposite side of the tub, the new drain would now be 5 feet from the current vent. I seem to have read that 5Â is the limit as to how far the drain can be from its vent. Is that right?

    Bookmark   June 20, 2009 at 11:57PM
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Before i could advise you on venting i would need to know what city & state your in.

    Bookmark   June 21, 2009 at 12:58AM
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I'm in San Jose California.

    Bookmark   June 21, 2009 at 1:28AM
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The California Plumbing Code is primarily based upon the UPC (Uniform Plumbing Code)

If you keep the line at 2" with a 1/4" per/ft pitch the UPC will allow 5' from the trap weir to the vent opening.

The trap weir is the specific point on the discharge side of the U portion of the trap where it transitions from vertical to horizontal, or to be more precise, the specific point where water passing through the trap would spill out of the U section and into the horizontal tailpiece of the trap.

If you were to downsize that line to 1-1/2" the maximum distance from trap weir to vent opening would be 3'6".

    Bookmark   June 21, 2009 at 1:56AM
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Although my P-Trap to vent distance would be 5Â (the limit), I think I will play it safe and keep the drain on the side closest to the vent. Moving it on the other side seemed attractive because keeping it close to where it is now means that the tub plumbing would have to be done on the wall bordering the kitchen (with kitchen cabinets behind) which, I assumed, would make for more difficult access in case of repairs. The other wall faces the garage. Even though the garage has wallboard, still, access to piping would be easier in case of repairs. The current pipes will have to move, because in addition to the fact that IÂm replumbing my whole house, the current pipes are now on what will become the long side of the tub which is an exterior wall anyway (unsuitable for plumbing, I read).

    Bookmark   June 21, 2009 at 12:50PM
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