PVC Spliced into Cast

This just occured to me - i'm planning on adding a bath group, and will have a vertical 3" pvc into a 4x4x3 combo on its back joining 4" cast - i was going to go with two hubless/banded couplings to splice this into the horizontal run.

perhaps relevant info:
there is a 2nd story bath (on main stack), kitchen, and sewer ejector (serving 1.5 baths, and kitchenett) upstream, and one 2nd story bath downstream of the intended splice. 1 revent and one secondary vent upstream from the main stack too. I need to do some work on the mainstack, since i'm removing a w.c.&lav which was wet vented so i'll have cut into it anyway. adding washer there, properly vented.

The real questions:

• Am i asking for trouble splicing a two foot pvc run into cast?
• Should i change the 20' or so of upstream 4" cast to PVC, and just have one coupling for the PVC to cast transition?

thanks - as always!

Properly support the cast before you cut it so it won't drop down and kill you. Also, you should anchor the lower portion too, in case it wants to fall into the basement because the horizontal piece that was propping it up is cut off. Since the stuff is built from the bottom up, that is not as likely to happen, but for the cost of a clamp...well worth the minor effort . If it is in good shape, you should be okay to leave it in place and patch in the new stuff. My unprofessional opinion...

already have a couple of 2x6s ready to hold the cut section - gotta do it when nobody is home, so i don't get flushed on. and yes, i don't want the copper stack shifting, since it already has pvc spliced in up in the attic. no need to make more work.

wonder if i should put a clean-out in with the splice - extra $10 would get one that is not in a "finished" part of the basement.

I hope you have at least one riser clamp for the vertical if you are cutting that!

clamp

Unless that vertical pipe is going straight up without any side connections, there is no way it could come down anyway, unless the house collapses with it.

A $5 clamp and the time to install it vs. the risk of the stack moving is worth the time and effort to me. In my case there was only a pair of sink connections above where I was cutting so I put the clamp in place in the attic.

I was thinking clamp in the attic too. it would be just my kinda luck to have it move, even tho there is a w.c. and tub attached (you should see that fitting...3x3x3 with a 1.5 on the 45 out the side!) neither of those drains is supported near the riser.

depending on my mood, i may just cap the 1st fl w.c. and run the new washing machine drain down to my splice. saves me a couple of cuts, and i can leave the old bath group in place until the next "big" project (gunna be alot of questions about the kitchen!)

hj said:

Unless that vertical pipe is going straight up without any side connections, there is no way it could come down anyway, unless the house collapses with it.

Click to expand...

Umm ... what if the side connection was only 1-1/2 PVC or a fernco or something weak? I wouldn't rely on that alone.

Jason