I asked to put a drain in for a toilet in my shop. I expected a pipe sticking out of the slab. I got a 3" PVC pip with foam around it making a 5.5" hole.
All the flanges I've seen have 6" spacing on the screw holes, but that puts it right at edge of the slab.
What are my options?

Can't post from flickr right now for some reason.
https://flic.kr/p/2jvCV4i

Is the concrete down a little around the hole? Where you going to set the flange on top of the level concrete or just below it.

We normally leave the pipe sticking out and then it gets cut off when the flange is installed. We also would set the flange on the concrete.

The picture is deceiving - the hole is the size of The styrofoam around the PVC - 5.5" dia. The black dots are where the flange holes are (stated 6" dia) & they are about 1/4-3/8" from the edge of the hole
The 3"/4" flange I bought goes outside the 3" PVC & on top of the concrete floor. I assume the larger hole is to allow for the angle of the flange, but if it was 5", I'd be fine.

There will be multiple solutions. I've never liked glued flanges and PVC in general. If that was my 'forever' shop, I'd remove the Styrofoam, wrap the pipe with foam packing sheeting to the thickness required to accommodate a 3" cast iron flange, and fill the void with high density cement. Then drill and anchor the flange, while packing and pouring the joint (or using a lead caulk substitute over oakum or cotton/linen strips of old cloth).

If using a PVC flange, same thing except if you are using a flange which glues inside the pipe, like a slip flange (do they exist?) you can cement up to the pipe.

That PVC would probably hold a toilet in place fine. I'd set the bowl alone, bolted smartly, and push grout or cement between the floor and the bowl. Not caulk. That'll give you a nice stable bowl which, along with the stationary PVC pipe, will protect the flange from someone in a hurry 'landing' on the bowl, shifting it, and breaking the flange.

quote:

I assume the larger hole is to allow for the angle of the flange

Yes.

My guys sometimes just put a coffee can over the pipe to get the right size for the flange to slide over the pipe.

I might try some longer tapcon screws into the cement.

Also, I always stick a rag or trash bag in the pipe to prevent anything from falling in.

Hydraulic cement around and into the concave area they left.
Make sure you use a longer tapcon for mounting the flange
Also, I’d avoid a synthetic ring, use a real wax one...god knows how long a synthetic one will last

quote:

Originally posted by comet24:

quote:

I assume the larger hole is to allow for the angle of the flange

Yes.

My guys sometimes just put a coffee can over the pipe to get the right size for the flange to slide over the pipe.

I might try some longer tapcon screws into the cement.

Also, I always stick a rag or trash bag in the pipe to prevent anything from falling in.

Being that I'm not experienced with drilling into concrete - done it a few times, but not many & not recently - I was expecting that if I tried to drill where those black dots are & used 1/4x2"L tapcons, I'd blow out the side of hole.
Am I overthinking this?

quote:

Originally posted by snidera:
Am I overthinking this?

Yes. The vast majority of flanges set around here are not anchored by anything other than the pipe. But the pipe is well-secured or so heavy it does not move. If you are concerned, a couple of ¼" or 5/16" drop-in plastic anchors will provide 'insurance' but that 3" pipe will not have any tendency to move. (You'd have to fill the void). This part below did not involve any anchors, just the pipe and a handful of mortar.

quote:

That PVC would probably hold a toilet in place fine. I'd set the bowl alone, bolted smartly, and push grout or cement between the floor and the bowl. Not caulk. That'll give you a nice stable bowl which, along with the stationary PVC pipe, will protect the flange from someone in a hurry 'landing' on the bowl, shifting it, and breaking the flange.

quote:

Originally posted by Woodman:

quote:

Originally posted by snidera:
Am I overthinking this?

Yes. The vast majority of flanges set around here are not anchored by anything other than the pipe. But the pipe is well-secured or so heavy it does not move. If you are concerned, a couple of ¼" or 5/16" drop-in plastic anchors will provide 'insurance' but that 3" pipe will not have any tendency to move. (You'd have to fill the void). This part below did not involve any anchors, just the pipe and a handful of mortar.

quote:

That PVC would probably hold a toilet in place fine. I'd set the bowl alone, bolted smartly, and push grout or cement between the floor and the bowl. Not caulk. That'll give you a nice stable bowl which, along with the stationary PVC pipe, will protect the flange from someone in a hurry 'landing' on the bowl, shifting it, and breaking the flange.

Thanks, I thought cement would be a PITA & still wouldn't solve my drilling too close to the edge problem. Not drilling period is even better.

quote:

Originally posted by snidera:
The 3"/4" flange I bought goes outside the 3" PVC & on top of the concrete floor.

All flanges [here] sit on the finished floor. After you remove the foam, you can see how firmly the 3" vertical comes through the floor. Perhaps a few inches of concrete will be wanted or maybe not.

I double nut/washer my closet bolts when possible. So the bolt is first attached to the flange with the extra washer and nut supplied in some kits.

Plain wax ring, as has been suggested. No fancy 'funnel-in-wax' or synthetic rings. You drop your bowl level on the wax. It should sit off of the floor. Then a careful rock / wiggle / screw motion [cannot reveal master plumber secrets on the open forum, but you get the idea] until the bowl is on the floor. Plastic closet bolt cap washers, metal washers, nuts, and careful tightening with a 7/16" hollow shaft nut driver [the one with, appropriately, a brown handle]. Not so tight you crack the bowl or begin yanking the pipe out of the hole. A handful of cement around the bowl's perimeter. When it is set up nicely, another snug of the nuts, then a cheese saw to cut the bolts down.

Center of flange is typically 12" from finished wall.

After the water is on the apprentice Pollywog gets a whirlie on the first flush.

quote:

Originally posted by Woodman:
A handful of cement around the bowl's perimeter.

Interesting. Are you saying you pack cement around the bottom of the stool after bolting it down?

I don't think I've ever seen that on a residential toilet before. Those generally are just held in place with the bolts.

Is that intended to prevent rocking/loosening?

Does that complicate things when it comes time to replace the stool, by requiring you to chip out the cement?

Does that cause issues by trapping water if the ring starts to fail and leak? (That's the argument I've heard against the old practice of caulking around the base of the stool.)

"Looks perfectly fine as is", says the guy who's spent time in Asia.

quote:

Originally posted by RogueJSK:
Interesting. Are you saying you pack cement around the bottom of the stool after bolting it down?

I don't think I've ever seen that on a residential toilet before. Those generally are just held in place with the bolts.

Is that intended to prevent rocking/loosening?

Does that complicate things when it comes time to replace the stool, by requiring you to chip out the cement?

Does that cause issues by trapping water if the ring starts to fail and leak? (That's the argument I've heard against the old practice of caulking around the base of the stool.)

Yes, when the bowl is set on a cement or tile floor, and I have it, I push cement or preferably grout or even thinset into the seam between the base of a bowl and a clean dry floor after the bowl is bolted to the flange. A dry towel will clean up the bowl and floor, followed 20 minutes later with a damp towel to remove hazing. This makes the bowl tight and stable. When checking batteries of WCs, I might only give the bowl a kick in front to confirm the connection. Plus a flush to feel the linkage.

Helps stabilize the bowl if the floor is slightly uneven in spots. Strengthens the connection against lateral stress, which can fracture a PVC flange. My clients may have 250-400 pound customers who use unconventional methods and etiquette when entering and using the water closet.

Complicate? A quality toilet should last more than one generation, but on commercial applications where one finds cement floors, and on tile floors, it is a non-issue. The cement chips off readily enough, and the new footprint typically covers most or all of the old footprint.

Trapping water? It may help prevent mop water from becoming trapped and mildewing under the bowl. Wax seals do not typically fail, but if one did, the cement would help keep the occasional spray contained. Ditto sewer gas. Caulk is not used because dirt becomes embedded into it and your job looks like crap.

I've used cement / grout on wood and linoleum as well, mostly to keep someone else from using caulk, but usually leave those bare. In my house, I've got off-white grout between the bone c.1992 bowl and white tile.