Question re: securing flange

[PlumbDIY]

Hello,

TLDR Summary: Is it necessary to screw a toilet flange into a concrete subfloor in order to secure it, or will the flange be sufficiently secured with glue + caulking the toilet?

Longer version: I just demo'd and re-tiled a bathroom which is resting on top of a concrete subfloor. The previous toilet plumbing installation did not have its flange secured to the floor with any screws, so there weren't any screw holes in the concrete. In fact, the previous installation was entirely against code, as it was using an offset flange, but even worse, the offset flange was simply cut and cemented into another piece of pipe in order to make it connect to the sewer pipe below, but that's a different story...

After having a plumber come and fix the underneath piping so that the pipe is the proper distance out from the wall and using the standard connection, I then finished tiling the floor. However, I'm wondering if I need to drill holes through the tile and the cement below and secure the flange with screws, or if I can simply glue the pipe together, caulk the toilet, and be done with it. Obviously the latter would be easier for me so that I don't have to drill the tile (I would be nervous about cracking), but it's more important to me that this is done right, so if that isn't an acceptable way of securing the flange, then I will certainly drill.

Thanks in advance!

 

[Jadnashua]

WHen you attach the toilet bolts and tighten them, you're pulling up at the edge of the flange. If it's an all-plastic one, you'll distort it, and eventually, it may break. If it's a metal ring, it can rotate around the plastic hub, so it won't hold much either. So, the only toilet flange you might be comfortable with not securing to the floor would be a cast iron one that was leaded to the pipe below...it's strong enough where it probably doesn't matter.

A diamond core bit and a spray bottle to keep the area wet will drill through a tile without issues once it is on the floor (assuming you got good thinset coverage and bond). You want to make sure that the through hole is big enough so your screw fits through easily, otherwise, you probably will crack things - the screw will act like a nice wedge.

If, when you cut your tile, you make notches on your tile saw for the screws, you don't have to try to drill holes through it, and a carbide bit will work fine going through the concrete.

 

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[PlumbDIY]

Got it, thanks for the reply! The flange is plastic, and from what you describe, it certainly makes sense to secure it with screws then. I assume I'll also need a hammer drill to drill the concrete under the tile, which I don't have, but I think I can rent those at HD for pretty cheap.

Thanks again.

 

[Jadnashua]

A hammer drill may just crack your tile...a regular one with a diamond core bit on it will be more reliable getting through the tile and should easily last long enough to drill your required holes. Depending on whether you decide to use plastic anchors in the concrete or a tapcon or similar screw, would determine whether a hammer drill might be useful going deeper into the concrete. But, either one will drill a few holes in concrete - a hammer drill, once you're through the tile, will drill faster, though. A nice tool to have in your arsenal, but for this, I wouldn't rent one.

Keep in mind that a good porcelain tile can be nearly as hard as diamond (actually, about the same hardness as sapphire)...carbide is much softer, which is why a diamond bit generally works better. Lowes sells Hitachi diamond core bits, but if you have some time, you can buiy less expensive ones on-line.

 

[PlumbDIY]

Yeah that sounds right. I felt like the hammer drill would pose the risk of cracking the tile but wasn't aware the diamond drill bit with the regular handheld drill would still be able to get through the concrete as well. I believe the 5/16" bit is the appropriate size?

I was planning on using the tapcon screws.

 

[Reach4]

Yeah that sounds right. I felt like the hammer drill would pose the risk of cracking the tile but wasn't aware the diamond drill bit with the regular handheld drill would still be able to get through the concrete as well. I believe the 5/16" bit is the appropriate size?

I was planning on using the tapcon screws.

5/16 would be a very large bit to drill into the concrete for a tapcon screw. It would be OK to make a clearance hole through the tile using the diamond bit. The Tapcon package will tell you the right diameter of pilot hole for the Tapcon. 5/32 might be the right size. They often sell the drill bit next to the Tapcon screws or even package a drill bit with some matching screws.

 

[Jadnashua]

A diamond core bit effectively grinds a hole through the hard substance...for longevity, it works best to keep it wet to both cool it and flush away the debris. Diamond is the hardest known substance, and will cut through anything. Concrete is much softer, and a hammer drill will go through it faster, but a regular drill will work, but if you're not careful, you'll overheat the bit. A good bit on a hammerdrill, and it's no worse than drilling through say hardwood. On a hard porcelain, carbide doesn't really work well, it's too soft. A hammerdrill shatters the material, not cuts it, assuming it is carbide on porcelain. NOw, a carbide bit on some other types of tile works really well, but not your typical porcelain.

 

[PlumbDIY]

Gotcha. I of course wasn't planning on using the hammer drill on the tile. I just meant that I would switch to that once I get through the tile with a regular drill. Thanks for all the help guys. Much appreciated.

 

[PlumbDIY]

Hey guys,

Just wanted to thank you again for your help. I did this work yesterday and everything worked smoothly. I bought a 5/16" diamond core drill bit for ~$20, and I went ahead and bought a hammer drill to get through the concrete after the tile. The 5/32" drill bit went through the concrete like butter and no cracks.

There were a couple of tapcon screws that I wasn't quite able to screw down to the floor all the way, but they're not obstructing anything so I'm fine with that. I think I just didn't drill quite deep enough into the concrete on those two holes, but I don't want to pull the screws out and drill more because it'll throw up concrete dust that I won't be able to clean out anymore, as the flange is now glued to the sewer inlet. I suppose having some debris remain there doesn't mean anything really, but I guess it would just bother me.

Thanks again!