Best way to fix my toilet flange

Hi. I have a concrete slab floor. There is a hole somewhat larger than the diameter of the pipe and there doesn't seem to be much if anything but air surrounding the riser from what I can see. The riser is 8-9 inches tall or so. The top of the flange is about 3/4 of a inch above the slab in the front and about 1/2 inch above the slab in the back. The flange is not attached to the slab at all. The flange is part metal and part ABS and attached to ABS pipe. One of the slots for the toilet mounting bolts looks to be in bad shape and rusted beyond use. I have removed the old congoleum so I can fix this problem. I plan on using a nice thick tile for the new floor. I want to fix this problem so my toilet can be firmly attached to the floor. Thanks

If as you describe, the toilet flange is 1/4" out of level, now is the time to fix it. Also, now is the time to figure out what the level of the new finished tile will be, and set the flange so that it sets on that. One way to be perfect is to prep the pipe, then lay the tile, then glue the new flange in place, snugged right down to the floor.


You can remove the existing flange with a hacksaw. Observe whether the pipe is INSIDE or OUTSIDE the flange socket. Make 3 or 4 VERTICAL cuts through the flange. ABS glue joints are usually such that once you have made these cuts, then with a large flat blade screwdriver, you can pop the pieces off.

From your description, your flange does not need to be much higher than it is now. You probably have plenty of length on the riser pipe to allow an adequate reinstallation of the new flange. I recommend an ABS flange with stainless steel ring ( not the blue or red painted rings)/

What do I do to make the flange level to the slab floor. It doesn't seem to move much, so would I need to do something at the bottom of the hole so I can shift the riser?

If the pipe that passes vertically through the concrete is crooked/out of level, the new flange will once again mimic this problem when you reset the flange.


Without seeing exactly what you have, you might be better off busting the concrete around the general area of this flange, cutting the pipe below grade and turning up a new pipe, level and plumb so that when you set the new flange, you know it's right and able to be properly secured to the concrete floor.

You are not off that much. If there is some play in the riser, you could tweak it vertical and shim it. If not, you can probably "fudge" the new flange as you press it on .

Thick wax will compensate for slight out of level. Your old toilet has been not leaking all the years, right? So, if you can get close, you will be OK. A waxless ring from Fluidmaster or Rectorseal are even better at dealing with out of level.

The one thing you want to avoid is a situation where the high side of the flange is TOO high, so the porcelain bottoms out, defeating the wax.

Could you post a picture?

I will take some photos and then I will remove the old flange. I will also take some photos after the flange is removed. The toilet did not leak, but when I bought the house, both toilets were broken at the bolt holes. When I installed the new toilets I did not try to tighten them a lot since I could see there was a problem. They have never been tight to the floor and that is what I want to fix. I was using a wax ring with the rubber cone. I am replacing the vinyl floor with mosaic ceramic tile. Before I put the new flange on I can shave a little off the riser so the new flange is a low as possible. Unless it looks easy I don't think I will try to remove and replace the pipe in and under the slab. Since it didn't leak I figure I will be ok if I can get the toilet to sit on the floor. Could or should I "shim" the flange so I can attach it to the slab? That way I could anchor it without bending it, giving me a solid flange to bolt the toilet to. Maybe a few washers stacked up to put the screw through?

Depending on the toilet, a flange that is not sitting flush on top of the finished floor may just be too high to allow the toilet to sit flat. This is apparantly what happened to the old toilets. When they tried to tighten the bolts to cause it to rest on the floor, because it was being held up by the flange, it broke. The reason it probably didn't leak is because of the funnel. This doesn't mean that if there was a backup, it wouldn't have leaked, though, since the toilet probably rocked a little, and would have broken the wax seal. The flange needs to sit on top of the floor, flush with it and be anchored, or you are likely to have similar problems. If you can get the old flange off, when gluing on a new one, there is a little give...not much, but a little, especially if the riser isn't quite the full height. As long as you get the new flange on and glued with most of the depth of the socket, it won't leak.

If you don't feel up to this task, it may be time to call a plumber.

When cutting your tile, if you notch slots where the anchors for the screws will go, it will be easier since then you won't have to drill through the tile (which can be a pain).

Well I went to cut the old flange off this morning and I forgot to take photos. While out shopping for a new flange I found one that seems to be a 4 inch that fits inside a 4 inch pipe. It also seems to fit fairly well on the outside of a 3 inch coupler. I am wondering if I can clean up the cut I made removing the old flange and just glue this one over the old coupler.

Also the coupler I found had the blue metal. I found PVC and an offset ABS and bare metal rings all stainless steel but I could not find a standard 3 inch ABS with a stainless steel ring. I was wondering if it would be worth buying the stainless ring alone and trying to switch it with the blue one. A little light trimming with the dremel tool on the ridge that holds it on should do the trick. Since the ring will be screwed to the floor and the ABS will be glued to the pipe I can't see how this could hurt. Would it be worth the trouble to get a stainless steel ring?


I slipped on this one to check the fit and here is what it looks like. I figured out that some insulation under the slab was holding the flange up keeping it from going on all the way. With a little pressure the gap was reduced to 1/8th of an inch. With the tile installed it should fit just right.

Now I have to figure a way to add some more concrete to the hole so I have a good surface to screw the flange to. Of course I haven't figured out how to do this and still be able to put the flange in the hole. If I put the flange on first it would be in the way. If I put the concrete in first how do I keep the space open where the ABS needs to go?

Well I found a 3 inch flange with a stainless steel ring. I decided to cross my fingers and go for it. I was afraid that I would just go from bad to worse. I was able to get the rest of the material off that was left over from the old flange. The new flange is a tight fit but I guess that is how it should be. Next, pour the concrete.

The flange is ideally installed on TOP of the finished floor, so with that additional height of the tile you are planning, you should be able to get it to sit flat on the floor. If you put some notches in the tile where the screw holes are, you won't have to try to drill holes in later. If you slip some cardboard, or maybe a sleeve of pipe the right size over the riser, you could then pull it out when the floor is down and glue the new flange in place.

I was waiting for one of the pros to comment, or I would have added more earlier, but this should work.

I had to fiddle with the last few I installed with my Dremel tool to get things the right height. I looked, but did not find an inside cutter, which would have made things easier. Everything that I wanted to remodel is now done, so it isn't a big deal. Good luck.