I had our house built 5 years ago roughed in for 1/2 bath in the basement. Now that I'm finishing the basement, I've run into a problem. All the walls are framed, drywall is up and bath is ready for toilet installation. Much to my chagrin, I realized now that the center of the soil stack is 20" from the finished wall, making the back of the toilet an unsightly 8" from the wall. I assume my options are limited. Either install an offset flange to get 2" closer, install a normal flange and deal with the gap using some shelving/cabinetry to disguise or rip up the concrete and extend the line 8"? Also, the stack is black ABS, can I safely use a PVC flange using the combination cement designed for both PVC/ABS. Also, what is the significance of Sch40/Sch80 and what is better to use in my situation? I tried to dry fit a flange for fit and it is extremely tight. Looks as thought the concrete floor which was butted up to the stack somehow contracted the pipe inwards to make it smaller diameter. Can I just rectify this with sanding if I decide to leave it where it is? Thanks

Glues for dissimilar plastics are not approved for use, so see if you can get the correct ABS flange.

As for the tightness, you might want to think about chipping away some of the concrete around the riser, if the fit is too tight and needs to be forced, you'll likely just end up pushing the glue out of the fitting.

And the twenty inch dilemma?

TOTO makes a line of toilets that sit over a flange that is bolted to the closet flange, and the floor flanges can be purchased that will work on 10, 12 and 14 inch rough-ins.

Thanks for the reply. I assume a 14" toilet would get me 2" closer to the wall, but would the measurement to the front of the bowl from the wall be the same with a 12 or 14"?? In other words, is a 14" toilet is just deeper front to back? Just curious. Also, I'm leary of chipping away concrete, not due to inability or lack of tools just concern over cracking the soil pipe. For this reason, I've hestitated on an offset flange. Any tips on minimizing the chance of cracking the pipe as I chip away at concrete around it to either alleviate the pressure from the outside of it or to install an offset flange. One last thing, can a 14" toilet be used in conjuction with a 2" offset flange? If so, that would get me 4" closer to the wall. Or is this pushing my luck? Thanks

Thanks for the reply. I assume a 14" toilet would get me 2" closer to the wall, but would the measurement to the front of the bowl from the wall be the same with a 12 or 14"?? In other words, is a 14" toilet is just deeper front to back? Just curious.

No, the toilet is the same no matter which floor flange kit you use.


Also, I'm leary of chipping away concrete, not due to inability or lack of tools just concern over cracking the soil pipe. For this reason, I've hestitated on an offset flange. Any tips on minimizing the chance of cracking the pipe as I chip away at concrete around it to either alleviate the pressure from the outside of it or to install an offset flange.

A chipping hammer like a Bosch Bulldog carefully used shouldn't really damage the pipe.

As for the offset flange, I'm not a big fan of those, especially in this day and age of low consumption toilets.


One last thing, can a 14" toilet be used in conjuction with a 2" offset flange? If so, that would get me 4" closer to the wall. Or is this pushing my luck? Thanks


If it were me, I'd sawcut and break up the floor and move it to where it should be.

Those offset closet flanges just don't work that well.

I agree 100% with Growlers answer. Stop attempting to compensate for the screwup and do it right. Good luck, Tom