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Old 06-20-2014, 01:01 AM   #1
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Default Help with bigger tub, bathroom remodel

I am replacing a 30"x60" tub/shower combo with a 40"x72" soaker tub. Lets use north for the front of thek existing tub where the drain is located. The new tub has the drain in the center by the front side (east). My drain piping is cast iron, and runs south under slab to main drain line about 6 feet. The distance from the new drain location to the old is about 2 feet. Can i get by with building up where the tub will sit and connecting new tub to old drain without busting concrete? Sorry i do not have any illustrations, i am posting from my ipad.

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Old 06-20-2014, 04:02 AM   #2
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Hmm. Is the new tub an above floor drain model? The drain pipe will have to slope down at least half an inch to be at the 1/4" per foot slope to the existing drain.
When you say building up, do you mean putting the tub up on a platform somewhat? I'm trying to remember if there are any code rules about steps up... I believe that having a stepdown to the tub is illegal bc of safety issues, but I'm not sure on stepping up. I think I've seen tubs with the step up though... So long as you build the floor up and make sure that the tub is fully supported underneath all around the pipe, you should be able to do it. I would not leave the tub just floating without something very solid underneath though.

I'm hoping someone who has experience with tub installs can give you a better answer.

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Old 06-21-2014, 12:01 AM   #3
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It is best if the trap is directly under the overflow of the tub, but the version of IPC I work under allows up to a 30" offset.
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Old 06-24-2014, 01:50 PM   #4
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Originally Posted by Byubuk View Post
...Can i get by with building up where the tub will sit and connecting new tub to old drain without busting concrete?...
You will have problems.

There will be an increased chance of odor in the tub drain, problems cabling the drain in the event of a blockage, and the tub itself will not be as stable as if you install it on the slab. With cast iron piping under the slab, having access for maintenance is critical. The biggest problems with cast iron drains serving tubs are:

1. Getting access to the drain through a cast iron or lead p-trap.
2. The p-trap itself.

Both of these problems get a chance for a reset with the proper installation of the new tub.

It will be much easier to remove a bit of concrete and relocate the drain than building a platform solid enough for the tub. You also avoid years of having an extra step up to the tub. I see DIY installs all the time like you are describing. They NEVER last and the customer is NEVER pleased with the result.

This is truly a case where it is easier to do it the right way.
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