Need advice for dealing with old in-slab toilet drain

[alane24]

I'm in the process of a bathroom+bedroom remodel in my basement and have encountered a snag in the bathroom with the existing cast iron pipe that is in the concrete slab. The house was built in '52, but I'm not sure how old the pipe is. What I do know is that it's 3.5" ID and isn't perfectly round. It goes about 4" deep before making the 90º bend toward the main.

The previous owner's just put wax rings right on the slab and bolted the toilet down with the studs that are set into the concrete. My plan was to cut those old studs off and tap-con a a new flange into the floor. However, none of the push in closet flanges I've tried provide a tight enough seal against the old cast iron pipe. I thought I could press in a 4" closet flange with the rubber gasket, but it's just too tight.

Do I have any other options outside of having my plumber break up the slab, pull the old 90º pipe out and replace it with PVC or ABS? I'd rather not go this route, but understand my options are probably limited.

Photos of pipe

These things haven't worked

 

[OLD TIMER]

They make expandable compression flanges. look them up. try to get a metal flange or you'll
be replacing it in a couple years.

 

[Sponsor]

 

[WorthFlorida]

Has this been capped off for a while or have you used it recently? Did the old toilet flush OK? I would worry about the rest of the pipe up to the wye of the main drain. That would mean cutting up the floor and placing new pipe. More important, is it vented properly? I almost sure that this was a floor drain at one time. Even in 1952 a cast iron flange would have been used and it would still be there and the pipe size also suggest that it was a floor drain. I would also suspect that the turn under the floor may have too much restriction (OK for a floor drain) for the new low gallon flush modern toilets and may not perform well. Your plumber probably could tell looking at it and know if there is enough venting.

Homes built in 1952 basement bathrooms were usually an afterthought when the family grew too large for the usually one bathroom homes built back then. After the remodel and there is drain issues, you don't want to chop up the new floor after that.

 

[OLD TIMER]

There's one way to find out. stick a clothes hanger down the hole, if you hit an obstruction then its a P-Trap and that would indicate a floor drain. if you pour water in it, should hold water if its a P-Trap.
also, if its not a P-Trap you should smell sewer gas if the drain is in service.

 

[alane24]

Has this been capped off for a while or have you used it recently? Did the old toilet flush OK? I would worry about the rest of the pipe up to the wye of the main drain. That would mean cutting up the floor and placing new pipe. More important, is it vented properly? I almost sure that this was a floor drain at one time. Even in 1952 a cast iron flange would have been used and it would still be there and the pipe size also suggest that it was a floor drain. I would also suspect that the turn under the floor may have too much restriction (OK for a floor drain) for the new low gallon flush modern toilets and may not perform well. Your plumber probably could tell looking at it and know if there is enough venting.

Homes built in 1952 basement bathrooms were usually an afterthought when the family grew too large for the usually one bathroom homes built back then. After the remodel and there is drain issues, you don't want to chop up the new floor after that.

Been capped off for a good couple of years, maybe longer. We never used the toilet when it was installed, but maybe once or twice. Previous owners left us with a very disgusting basement so we ignored it and I demo'd the room. I can hear air and water when the upstairs toilet is flushed so I know that it's definitely vented and likely not obstructed as I've always had it covered.

My plumber said that he could hammer out the current elbow and install modern pipe for $125-$175. Sounds like this is probably the best option for hassle free use down the road, eh?

 

[alane24]

They make expandable compression flanges. look them up. try to get a metal flange or you'll
be replacing it in a couple years.

I haven't seen anything that has an OD that would fit my 3.5" ID pipe, the big box stores sell 3 and 4" expanding flanges and neither of those fit. 3" is far too small and I can't even encourage a 4" to fit.

 

[alane24]

Spoke with my plumber and he's willing to come in and open up the basement slab with a jackhammer and replace the old 90º with modern plumbing.

Can I get some info on how this will work? I'm afraid of cracking the slab. The foundation wall is only 12" from the drain so if it were to crack it seems like that would put me up sh*t creek in a real hurry.

I'm curious if there are other options I have besides jackhammering out the old pipe. Wondering if I could install new studs in the slab that are longer and centered over the hole, then install one of these along with a wax ring once the floor is tiled.

 

[Mliu]

To prevent the concrete from fracturing beyond the work area, use a concrete saw (or angle grinder with a concrete blade) to cut around the perimeter of the work area. For example, cut a 12" x 24" rectangle around where the elbow is located. That way, if the concrete cracks during sledgehammering, the crack will stop at the perimeter cut.

 

[Reach4]

I'm curious if there are other options I have besides jackhammering out the old pipe. Wondering if I could install new studs in the slab that are longer and centered over the hole, then install one of these along with a wax ring once the floor is tiled.

Add studs in the slab? If you want to screw something to a slab, you use screws made for concrete, after drilling the right-size holes first.

If you can get your 3.5 inch ID hole clear in the right place, you could use that ring you pictured or other thing. The ring's job is to let you mount the closet bolts. However you have closet bolts. So maybe just put wax on your newly cleared-out hole.

I am not a plumber.

 

[alane24]

To prevent the concrete from fracturing beyond the work area, use a concrete saw (or angle grinder with a concrete blade) to cut around the perimeter of the work area. For example, cut a 12" x 24" rectangle around where the elbow is located. That way, if the o concrete cracks during sledgehammering, the crack will stop at the perimeter cut.

Thanks. My plan would be to do a dry cut with a concrete blade and my circular saw. Thinking it would be wise to have a helper suck the dust up a shop vac. I’ll be doing my work in a newly finished room and would like to keep it clean.

 

[hj]

If you called me, I would do it the right way and make an annular ring in the concrete around the pipe and install a new cast iron flange using lead and oakum.

 

[WorthFlorida]

Thanks. My plan would be to do a dry cut with a concrete blade and my circular saw. Thinking it would be wise to have a helper suck the dust up a shop vac. I’ll be doing my work in a newly finished room and would like to keep it clean.

If this floor pipe does drain, use a garden hose and dribble water on the cut to help cut down on the dust. Just because you hear noise from the drain when the upstairs toilet is flushed it doesn't mean that this pipe is properly vented. It also could mean that the p-trap is dry if there is one but toilets do not use p traps and it is 12" from the wall so it may in fact have been a properly installed & vented toilet connection 67 years ago. Cutting is up for new pipe is a the right way to go.

 

[Mliu]

Thanks. My plan would be to do a dry cut with a concrete blade and my circular saw. Thinking it would be wise to have a helper suck the dust up a shop vac. I’ll be doing my work in a newly finished room and would like to keep it clean.

Just so you know, you'll probably ruin your circular saw cutting the concrete. It's very hard work on the motor and gears, and the abrasive dust will get into everything, including the bearings. My advice would be to go to Harbor Freight and buy one of their cheap 7" angle grinders. Add a concrete blade and you're set. I would put a small amount of water in the concrete cut line to minimize dust, but make sure your tool is connected to a GFCI outlet.

Whatever you use to cut the concrete, the fine powdery dust will get everywhere. It's messy work. A shop vac will help, but will not solve the problem (plus, the shop vac filter will quickly clog due to the copious amounts of very fine dust). I recommend enclosing the work area from ceiling to floor with plastic drop cloth taped completely. You MUST use a respirator (in addition to safety glasses, earplugs, and gloves), as concrete dust is cancerous to your lungs. After you finish cutting, leave the work area, keeping the plastic "tent" closed until all the dust settles to the floor. Then sweep/vacuum as needed.

 

[Reach4]

I had previously misinterpreted your photo.

The previous owner's just put wax rings right on the slab and bolted the toilet down with the studs that are set into the concrete.

What would be wrong with that?

The Danco Hydro Seat might appeal to you.

 

[OLD TIMER]

I like HJs idea.

 

[alane24]

I had previously misinterpreted your photo.


What would be wrong with that?

The Danco Hydro Seat might appeal to you.

Not saying there was anything wrong with it, I was just surprised to see it this way. Installing a flange as it stands in its current state isn't possible as there's nothing on the market that I have found that would work with a 3.5" ID pipe. Everything is made for modern 3 and 4" pipe. I wonder what kind of seal I would get with that Hydro Seat.

If this floor pipe does drain, use a garden hose and dribble water on the cut to help cut down on the dust. Just because you hear noise from the drain when the upstairs toilet is flushed it doesn't mean that this pipe is properly vented. It also could mean that the p-trap is dry if there is one but toilets do not use p traps and it is 12" from the wall so it may in fact have been a properly installed & vented toilet connection 67 years ago. Cutting is up for new pipe is a the right way to go.

Thanks for the info. There is a vent pipe that is behind the finished wall in the bathroom so I know for a fact it is vented. That vent runs up into the attic and out the roof. The upstairs bathroom is directly above this basement one and uses the same vent.

Just so you know, you'll probably ruin your circular saw cutting the concrete. It's very hard work on the motor and gears, and the abrasive dust will get into everything, including the bearings. My advice would be to go to Harbor Freight and buy one of their cheap 7" angle grinders. Add a concrete blade and you're set. I would put a small amount of water in the concrete cut line to minimize dust, but make sure your tool is connected to a GFCI outlet.

Whatever you use to cut the concrete, the fine powdery dust will get everywhere. It's messy work. A shop vac will help, but will not solve the problem (plus, the shop vac filter will quickly clog due to the copious amounts of very fine dust). I recommend enclosing the work area from ceiling to floor with plastic drop cloth taped completely. You MUST use a respirator (in addition to safety glasses, earplugs, and gloves), as concrete dust is cancerous to your lungs. After you finish cutting, leave the work area, keeping the plastic "tent" closed until all the dust settles to the floor. Then sweep/vacuum as needed.

Good call on the angle grinder, that's the way I'll go. Wondering if I could use a cold chisel and sledgehammer to break up the slab rather than rent an electric jackhammer. Thanks for all of the advice.

 

[Reach4]

I wonder what kind of seal I would get with that Hydro Seat.

You put a wax ring under the Hydro Seat, so you would get a very good seal.

 

[Mliu]

Wondering if I could use a cold chisel and sledgehammer to break up the slab rather than rent an electric jackhammer.

The area you're removing is very small, like 12" x 24". You could make some extra cuts across this area so you're dealing with smaller chunks. As long as you're cutting deep enough to get through any rebar or reinforcing mesh, you should be able to break up the concrete with some well-directed blows of a sledgehammer without a chisel. But I would make sure the cast iron pipe is separated from the surrounding concrete by cuts so that the concrete you're hammering on isn't transmitting forces to the pipe (you'll want to do this even if using a jackhammer). You don't want to put a crack in the pipe somewhere under the slab. After you break up your working area, use a pry bar to leverage the chunks of concrete out. Again, avoid pushing your prybar or the concrete against the cast iron pipe.