Toilet drain 4” connecting to sanitary tee that drops the poop to 3” - the outcome?

[isotope]

A couple have their concrete basement floor completely opened up on one of these home improvement remodeling shows. They are moving the toilet and plan to install a new 4” toilet flange and new 4” toilet drain pipes to the existing sanitary tee. Oops! They realize that the original sanitary tee connecting the toilet drain and stack is only 3”.

Yeah. This actually happened on a show I was watching, but got tired of the commercials, so I turned to watch something else. Anyway, I didn’t see what happened. What could have been done? I’m guessing that the best course of action would be to just rough in the toilet flange and toilet drain back to the old 3” size and leave the old 3” sanitary tee in place.

 

[Terry]

The entire line should have been 3" if downstream it's 3".
It's okay to have a closet bend that changes to 4" at the flange, which is vertical and higher than the line.

 

[Sponsor]

 

[isotope]

The entire line should have been 3" if downstream it's 3".
It's okay to have a closet bend that changes to 4" at the flange, which is vertical and higher than the line.

Huh? Are you saying it’s ok for the toilet flange to be 4” and then you drop down to a closet bend that reduces to 3” and then stays 3” downstream? I thought it was always a no no to reduce any DWV piping to a smaller size anywhere.

 

[Terry]

4x3 closet bend.

4x3 closet bend.

These maintain the flow.
Going from 4" pipe to 3" pipe isn't done though.

 

[FullySprinklered]

The closet el is my preferred way to do it. Reason is, you can stub up the 4" and leave it. After the tile goes in, cut the pipe flush and install a flange that fits inside the 4" pipe. The flange ends up right where it supposed to be with the least amount of trouble.

Dropping it into a tee is frowned upon.

 

[isotope]

In all my years, I’ve never used a closet bend 4” to 3” closet elbow. This isn’t prevalent in Australia, New Zealand where I’ve worked. Generally, in Australia, New Zealand... and I’m not sure, but maybe UK as well... toilet piping is done with 100mm (ie, approx 4”) piping. And we use a long sweep elbow. We don’t use 4” to 3” closet elbows. We don’t even use these messy wax rings for a toilet flange, but instead use a O-ring receiver type of system.

Anyway, I know this is drifting away from my earlier original post, but I have a new question... Is it common in USA to use a 4” toilet flange (messy wax ring of course), attached to a vertical 2 foot long 4” pipe, then attach to a 4” to 3” closet elbow, then everything downstream remains at 3” piping???

 

[Reach4]

We don’t even use these messy wax rings for a toilet flange, but instead use a O-ring receiver type of system.

Into the wall usually?

O-rings would seem to require more precision receiver placement and/or less adjustabilty of the toilet.

but I have a new question... Is it common in USA to use a 4” toilet flange (messy wax ring of course), attached to a vertical 2 foot long 4” pipe, then attach to a 4” to 3” closet elbow, then everything downstream remains at 3” piping???

No. That closet flange thing seems to be the exception.