View Full Version : Gap between toilet drain flange and bathroom floor tile

09-24-2011, 11:04 PM
Hi there,

Have two questions on a toilet flange and the bathroom floor tile:

1. I wonder if for an installation of floor tile in the bathroom, is it supposed to have no gap (and sealed if there's any) between the floor tile and the drainage pipe that comes up and connects to the bottom of the toilet.

The reason is I do see a small gap between the surrounding floor tile pieces and the toilet drain flange. Is that acceptable?

If there's a gap, if there is water on the floor tile, would there be a possible water leak thru' that gap into any structure below the toilet?

FYI--I'm using the FluidMaster Wax-Free Toilet Bowl Gasket, so there isn't any wax from a wax ring to seal up the gap I just mentioned.

2. Also, the toilet flange is level with the floor tile instead of sitting right on top of the tile. Would that pose any problem? The toilet does appear to be a bit wobbly after I fastened it to the flange.

Thx... .

Gary Swart
09-25-2011, 12:12 PM
A toilet flange is supposed to set on top of the finished floor (no gap or space). Then the flange must be screwed through the finished flooring and into the sub floor. You can get away with a flange being slightly recessed below the floor by using a thicker wax ring or the wax free seal you mention. You might be OK with the flange raised above the floor if, and only if, the plumbing was cast iron. PVC or ABS pipes would allow the flange to move, and that means the seal would be compromised. Your best course of action is to have a new flange installed.

09-25-2011, 12:41 PM
You will also want to install shims to ensure that the toilet is stable. Then, you should caulk around the front 3/4 of the toilet (leave the back open).

09-25-2011, 07:10 PM
In an ideal world, the flange is always installed on top of the finished floor. If the flange is solidly screwed down to the subfloor and then tiled around, it will still work fine if it is flush.

If the seal leaks, the water is going to run under the flange and into the space below no matter if it is tiled under the flange or not.

If the toilet can rock, the seal will leak.

09-26-2011, 12:48 PM
Thx so much for the info.

It's a cast iron drain pipe under the toilet. It's hard to see completely as the floor tile is already installed but as I looked and there were no screws that fastened the flange to the subfloor. The flange just sat on top of the subfloor I think. Is that still ok?

> A toilet flange is supposed to set on top of the finished floor (no gap or space)

I think the hole made in the subfloor is rectangle it's a round cast iron pipe. There's definite air gap around the pipe.

I do see a clear air gap as I can see the subfloor (and under the subfloor) from the top of the flange.

How do people seal up any gap between the flange and the surrounding floor?

> If the seal leaks, the water is going to run under the flange and into the space below no matter if it is tiled under the flange or not.

Are folks referring to the seal from the wax ring? I'm using a wax-free seal so there's no wax that covers the area between the outside of the flange and the finished floor. Do people seal around the flange (between the flange and the surrounding finished floor) and what additional seal is used if I'm just using a wax-free seal? Say, if someone just drops a bucket of water onto the finished floor in the bathroom -- water would definitely leak thru' the outside gap of the toilet flange thru' the subfloor into under the toilet then?

I'm really looking to seal up the gap between the flange and the surrounding floor... . Note that the floor tile is already installed. And I'm using a wax-free seal. So don't know how to seal up this gap... .

09-26-2011, 01:20 PM
Often, CI is strong enough so it can get by without being anchored, but it is supposed to be. The flange should be on top of the finished floor, and then, you'd be able to anchor it. I probably wouldn't worry about the gaps around the flange now. If you could get under there, you could add some blocking so you could anchor things, but with the toilet installed and then caulked to the floor, it shouldn't move. When using a wax ring, it would only seal from the horn of the toilet to the flange ring...it would do nothing about gaps around the flange to the floor (which shouldn't be there).

09-26-2011, 01:25 PM
I can stick my last finger into that gap around the outside of the flange, so it's not a hairline gap (perhaps the hole in the subfloor was cut too big... ). I can see under the subfloor thru' that gap. So looks like water can definitely go thru' that and down. What'd you suggest to fix that gap?

And then I wonder, if I ever do install a flange and a new floor, how do I ensure no gap between the flange and the finished floor? I have seen video showing a floor tile cut-out as a rectangular area around the flange. Since the flange is circular, there's definite gap in that case. Or is that video showing wrong set up for the floor tile around the flange?

Or am I missing some details here?

Thx much... .

09-26-2011, 01:36 PM
A square hole is a handyman's thoughts on what will work, not what should be there. Unless you overflow the bathtub, and regularly have water on the floor, this isn't an issue. To fix it now, risks cracking tile. You could take a square of ply so it would fit between the joists, then cut a hole in it to fit around the pipe, then cut through the hole so you can put it up under the hole from below. Some screws and construction adhesive would then hold things laterally, and let you screw down into it. You could make a smaller square to fit up even with the existing subfloor and glue it to the new piece below.

Personally, I'd just consider trying to put some blocking there, glued and screwed to the subfloor from below, and ignore the rest. Just make sure you don't use screws that are too long, or you'll crack your tile (as would trying to nail it in place). If you have a leak, water will find its way down there regardless. The goal is to do seal the toilet to the flange properly so that doesn't happen.

09-26-2011, 03:47 PM

Thx for the suggestion. Looks like things weren't done right when the flange/floor was set up before.

If someone were to do it right when doing the cut on the subfloor/finished floor (e.g. tile), should it be

- a round hole in the subfloor (instead of a square hole) that fits the underside of the flange snugly so there's no gap?

- to install a floor tile, the tile should be a 'round' (instead of a square ) opening and fits the underside of the flange snugly also (isn't this hard to do to cut & shape the tile that fits 100% the underside of the flange)?

I'm planning to do a tile floor in the other bathroom later on so I want to make sure I see that 'll do things right... .

09-26-2011, 04:00 PM
The subfloor and tile should fit underneath the flange such that when you screw the flange down, it is fully supported by the finished floor, and the finished floor is supported by the subflooring. There are lots of techniques to cut holes in tile, some take more skill than others. But, since the toilet covers most of it, it isn't that big a deal. You can use a grinder with a diamond cup wheel, or your wetsaw. If you cut front the back, with lots of wedges, you can crack them out. There are some examples at www.johnbridge.com (http://www.johnbridge.com) if you use their search function. to avoid having to drill holes in the tile, a little planning and notches in the tile mean you only need to go through the subflooring.

09-26-2011, 11:02 PM
Thx much for the info--v. helpful.

For the current fix on the finger-size gap around this flange, I wonder if I don't do add any plywood to fill up from under, is it still ok for the CI pipe to stand on its own. I'd just perhaps spray some expandable foam to sort of seal up the air gap around the flange so for slight water issue it won't leak below the toilet.

Would that be good enough?

Thx... .

09-27-2011, 09:55 AM
Again, if you have a water problem, nothing you do about that will matter. You need to ensure it is sealed up well. CI is pretty strong, but it still should be anchored for maximum security in a wooden subfloor situation. If you flood the bathroom, it's still going to go down whatever holes it finds. It just shouldn't happen from the toilet, if it is installled properly. You can add some foam, but other than air leaks and feel-good, it probably won't make much difference. A leaded joint on a CI fitting is quite strong, but it is also quite heavy. It'll be fine if it doesn't get knocked around.