I am remodeling an upstairs guest bathroom, and have taken out the old cast iron tube (3 wall enclave with right side drain). I have purchased a Kohler Villager replacement tub, also cast iron to replace it. The problem, however, is in the drain plumbing. The previous tub was a standard 5' tub, however it was old and I cannot recall if it was also 30" wide. I'm pretty sure it was, considering the finished wall on the fixture side is 30" from the connecting wall. However, the drain for the old tub is only 12-1/2" from the back. The new tub has the drain located dead center in the tub, placing it 15" from the wall. Thus, if you are standing in the tub, facing the fixtures/drain...the drain is now approx 2 and 1/2 inches to the right of the old drain. This is where I want to pull my hair out, because directly underneath this new drain location is, of course, A FLOOR JOIST! I have no idea how I'm going to re-route the existing plumbing to accommodate for this new drain location. I am looking at having to cut a floor joist in order to place the drain/p-trap assembly. Further complicating things is that the DWV piping is cast iron and, although sturdy and leak free, is very intricate with lots of hubs and also comes directly off of a large Y fitting, with the other branch of the Y going to the nearby master bathroom in the next room over. Even if I was to cut into or remove a section of the floor joist, I don't have a lot of room to re-route a new p-trap since it is currently coming directly out of one of the hubs on the Y. Is there an acceptable way to remove a section of joist to reconfigure the plumbing for the new drain? Or does anyone know of they make standard 60"x30" inch tubs with the drain located off center, preferably off center to the left. If anyone knows, or has suggestion, by all means, I can use all the help I can get. Thanks!

You are learning first-hand one of the golden rules of plumbing: It's harder to move something by 2" than it is to move it by 2'.

What you need to do probably can be done, but will take a lot of work to pick up that extra 2-1/2" that you need. A section of the floor joist will need to be removed and two headers will need to be installed connecting the two joists on either side of the cut joist. This will keep everything strong and carry the load of the cut joist. How far back you need to make your cuts depends on how much room you need for your drain plumbing.

On the plumbing the best way it so cut out the cast pipe as far back as you can (even beyond any Y's or T's). Then rebuild with PVC drain. This way you can move some of the other drain parts out of the way of your tub drain.

Neither of these is easy so you may want to hire a pro to do this. Most plumbers could do it and any handyman types could too.

the other thing you could do is take the piping past the joist and curve it back. probably against code in one section or another as you have added a restriction to flow, although as a bathtub there's plenty of back pressure to not leave any old water behind.

if you did that, you would have to sister the joist previous, because you will be cutting it down to have the tub drain into an angle right away. screws and glue.

much better to cut back the drain line, drain to an angle and right into the P-trap from there, and thence to your drain line. hey, if it means raising the tub on a pedestal a stud width high, that's worth doing if you can avoid fooling with the structure or doing ugly things to the drain. put a step height in there, use a contrast tile, set a spot light, make it a design element.

on drains, the general idea is to have a regular free fall of a quarter to a maximum half inch per running foot straight as possible to the stack. water doesn't run uphill, and it doesn't like to go a ways and backtrack. that is called a restriction of flow, and is a very basic no-no.

I hope you have a vent run between the P-trap and the stack as well. draining 40-50 gallons of water calls for a lot of air behind it.

This message has been edited. Last edited by: swschrad,

i am a plumber. maybe i can help you
for the tub to drain correctly and fast you will need to cut the floor joist and head it off
that means cut it out of the way and add 2 peices of wood. the same size as what you cut out
making a "box" around the drain
then carpenter work out the way the fun begins
you need to demo the old ptrap.
your new tub is designed to be installed with out sheet rock behind it. and you will need to add a 2x4 on the wall to support the apron of the tub
thats the long end , against the wall
the tub sits on this 2x4 so it will not 'rock' when you are singing in the shower
after tub is slid into position and levaled
a waste and overflow and ptrap ned to be installed
post back when you get that far
when you cut out old trap, use a "MISSION" BAND
to connect the old cast to pvc piping
or a cast x pvc eztite gasget if connecting to a hub
remove the old piping from the hub, if its a lead caulked joint, use your torch to melt the lead
and pull the oakum out
if all this scares you call a plumber
po

This message has been edited. Last edited by: Frodo,