Replacing 50yo iron combi wye with PVC

[Guy48065]

I have a rust pinhole in the cast iron sanitary wye that makes the final turn before exiting to my septic tank. I'd like to replace with PVC but I'm concerned I won't be able to fit it in without major surgery. All the piping in this area is fixed in place by a built-in cabinet.

The existing wye is a 4x4x3 no-hub and it's only 6" from the top of the 4" to the open end of the 3". The equivalent PVC fitting--with hubs--is much taller.

What's my approach here?

 

[GReynolds929]

For starters your drain can't be reduced like that. It has to remain it's largest size all the way to the septic. Looks like both of those cast combos need replaced.

 

[Sponsor]

 

[Guy48065]

3-inch lines feeding into 4-inch exit.

 

[GReynolds929]

3-inch lines feeding into 4-inch exit.

What size are the lines marked in red? They look bigger than 3". Pictures can be deceiving though, so I could be wrong.

 

[Guy48065]

View attachment 96352What size are the lines marked in red? They look bigger than 3". Pictures can be deceiving though, so I could be wrong.

All those are 3" and feed into 4x4x3 no-hub wyes.

What is the proper name for that robot-shaped hub that my 3-in lav drains feed into?

 

[hj]

t looks like a PVC "SO-Vent" fitting, which would be unusual in a single story residence.

 

[John Gayewski]

View attachment 96352What size are the lines marked in red? They look bigger than 3". Pictures can be deceiving though, so I could be wrong.

Those could be no hub adapters rather than reducers. They do look like reducers.

 

[John Gayewski]

There is probably no direct replacement in pvc that will fit. Your gonna need to buy a new combo in cast iron. There are some no hub pvc fittings, but availability is limited.