Help with lav/sink and tub drain

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brian717

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Hi fellas.

I'm redoing my bathroom and ran into some old out-of-code plumbing on the lav sink and tub / shower drains. Basically, both the sink and the tub drain to the same drum trap, which then drains into a 2" vertical cast iron pipe that connects back to the main 4" cast iron stack for vent / drainage. I've mocked it and the materials up in the following crude MS Paint image:

http://imgur.com/Jaw3dRK

I would like to remove the drum trap and put in some new PVC P-Traps for the tub and sink. I was thinking I would cut out a section of the 2" cast iron pipe and insert either a no-hub cast iron sani tee or a PVC sani tee with shielded couplings (if the latter is up to code). I've mocked this up as well:

http://imgur.com/3hAZRS9

I was just wondering what you guys think of this? Do you see any issues with this set up? Since I'm tearing things up anyway, I'd like to bring it all up to code, if at all possible. I'm in MA, in case there's someone more well-versed with the code than me.

Thanks!
 

Cacher_Chick

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On a vertical stack, the fixture with the highest connection to the stack (in this case, the lav) is considered vented by the stack. The tub trap must be vented before the connection to the stack. The trap arm between the trap and vent cannot drop vertically or for that matter, exceed 1/4" per foot.
 

hj

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We cannot tell if the drain line is vertical or horizontal, so cannot answer the question. Technically, people in MA are not allowed to do their own plumbing installations.
 

brian717

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Thanks for the feedback, I appreciate the help. The 2" cast iron drain / vent is vertical, while everything running into it is horizontal and 1.5".

I was under the impression the 2" drain from the lav above would act as a wet vent for the tub below it in the stack. I thought the MA code allowed for that... though I'm not 100% sure. To be completely sure, would it work to run a vent out of the top of the tub drain into the stack above the lav drain? Also... the MA code mentions new fittings and pipe installed in a pre-existing stack should be of the same material as the current stack, but I've seen many people replace sections of a cast iron stack with PVC or ABS... is this not up to code?

Thanks again.
 

hj

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Technically, No. In most cases they allow ONE transition between materials, then the continuation can be the second material, but any connections to the original pipe have to be the same material.
 

Cacher_Chick

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A plumbing supply store can set you up with no-hub cast iron wyes or tees which are installed with banded couplings, much like one would if they were doing a transition.
 

brian717

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Thanks again for all the help. I'm going the no-hub cast iron route for the vertical portions in the 2" stack, but will transition from cast to PVC for the horizontal runs to the fixtures. I believe since there will only be one transition on the way to each fixture and there's never a plastic portion supporting the weight of cast iron, this would be up to code.
 
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