How to Install an Offset Toilet Flange

I ran into a situation where someone had installed a toilet with a 15-inch offset from the finished rear wall of a bathroom. The typical offset is 12-inches for most residential toilets. As a result, there was a full 4-inches behind the toilet, making it look like it was trying to participate in the activities of the bathroom rather than sit quietly until needed. While this would seem to be a hopeless situation – I mean who wants to completely remove and cut out a new toilet drain hole? – there is a way to make it right. Shop at your local home improvement store or neighborhood hardware store and you’ll find a device called a toilet offset flange. This product is designed to give you approximately 2-inches of extra distance in any direction from the existing toilet sewage pipe. Here’s what it looks like:

As you can see, the flange is primarily PVC, with a metal or PVC flange ring that circles the top that can be rotated  to center the bolts as needed underneath the toilet. This also gives you one more advantage: the toilet can be moved in any direction, so you can move it backwards, or even diagonally if needed.

Supplies (based on 4″ PVC sewage pipe, adjust accordingly for 3″):

• Offset toilet flange
• 4″ schedule 40 PVC pipe
• 4″ schedule 40 PVC coupler
• One-step PVC cement
• Wax ring and bolts (double-thick kit)
• Great Stuff Window & Door expanding foam

Tools:

• Reciprocating saw
• Cordless drill
• Dremel or other rotary tool with cutting blade
• Adjustable wrench
• Bolt cutters or metal saw (reciprocating saw or oscillating multi-tool)

In our case we were interested in moving it straight back, so here are the steps on How to Install an Offset Toilet Flange:

1. Remove the existing toilet by using an adjustable wrench to remove the nuts on the retaining bolts and lift the toilet off the existing flange.
2. Dispose of the old wax ring and clean the toilet base in preparation for the new  flange.
3. Stuff a thick rag or disposable towel into the existing toilet hole to block the sewer gasses from escaping into the room.
4. Plan how your new offset flange will fit. They typically come so that the base of the flange will fit over a 3″ Schedule 40 PVC pipe, or INSIDE a 4″ Schedule 40 PVC pipe. You want to do your best to make sure that waste flows down into the sewage line without being impeded by seams or anything that could cause a backup or restrict the flow of waste (aren’t you glad we’re using such “proper” terminology?).
5. Remove the old flange by removing the screws that secure it to the floor and using a Dremel or similar tool to cut around the piping from the inside to allow a new pipe to be connected. If you have a crawl space, you can cut the pipe from below with a reciprocating saw. You want to end up with a pipe that you can couple to the new offset flange, so measure the depth to see that you will be able to successfully use a coupler or, at worst, a rubber boot to join the two new pieces together.
6. Remove and discard the old flange.
7. Use a reciprocating saw to cut out where the offset flange will need to be in order to set the toilet back further towards the wall. This is best done with either a wood or a demo blade and you may need to angle the blade slightly to avoid cutting away too much material. Remember, you are going to need the new flange to fit snugly so that you have remaining wood to fasten it securely to the floor.
    
8. Dry fit the new offset flange until you are satisfied with its fit.
9. Apply a generous amount of one-step PVC cement to both the pipe and the end of the offset flange and fit them together. Alternatively, if you find you need to use a rubber boot, fit the boot over both pieces and secure with a flat-head screwdriver. Typically a boot will only be possible with a crawl-space environment, since you need access to make it work.
   
10. If there is any space along the front of the new offset flange (and there should be, if you did it correctly), fill it with Great Stuff Window & Door expanding foam. If you’re careful you can get it so that you don’t have to trim it back, but if you overdo it, just wait until it’s dry and use a razor blade to trim it flat.
11. Insert the new hardware bolts into the offset flange.
12. Place the double-thick wax ring on the flange, waxy side up, with the short rim inserted into the flange opening.
13. Replace the toilet by carefully lining up the holes at the base with the bolts sticking out of the new offset flange. This step is much easier with two as the toilet itself tends to block your view of the flange bolts. Work the toilet down until it is seated flat onto the floor. Secure the bolts with the washers and nuts provided.
14. Clip the bolts to length with a pair of bolt cutters or a metal blade on your multi-tool or reciprocating saw and place the plastic cap (if included) to cover the bolts.

That’s all there is to it. Now you can “enjoy” your newly-moved toilet as if it were properly installed to begin with. This is a relatively easy project to undertake and pre-planning will usually determine whether or not you have an easy or tough time of things.

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