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Plumbing in the Home/Replacing old toilet without closet flange


Existing toilet
Existing toilet  
toilet drain
toilet drain  
QUESTION: I am trying to replace an old toilet.  I think it was installed in the early 1930's and it is now leaking at the bottom and the tank.  The toilet is install on a concrete floor as shown on the attached photos.  The first piece of drain pipe is a terracotta 90 elbow.  It also appears the toilet was set in a mortar bed as the photo shows about a 3/4 inch mortar bed above the floor, there is no wax ring nor any space on the bottom of the existing toilet for one.
Please advise how to install a new toilet that is designed for a closet flange as there is no existing flange to use.

ANSWER: Hi Eric,
First, there is always room for a wax ring. No toilet is totally flat/flush on the bottom. There is always a recess around the outlet that will accept a wax ring.

The purpose of the closet flange it to provide a place for the bolts that hold the toilet down to the floor. Without a flange or closet ring, the bolts will need to be set into the concrete floor, possibly with epoxy.

Clean all the old mortar away and get a flat surface to work on. Dry fit the new toilet base and get it lined up over the waste inlet in the floor.  Mark where the hold down bolts need to go. Remove the base and drill in and set the bolts.  

Next, get a couple of wax rings. One with a plastic "horn" and one plain. Make sure they are warm enough to easily deform/conform to the floor and bottom of the toilet base as you press it into place over the bolts. You may not need two rings but if you do, use the one with the horn/funnel on it first and stack the plain one over that if needed to fill any gaps.  Pick up the toilet bowl between your knees at it's balance point by straddling it and "duck" walk it into place and lower it straight down over the bolts. Push down with your arms straightened and maybe slightly rotate the bowl while pushing down on the bowl until it is sitting flat on the floor.
Install the washers and nuts on the bolts and snug them down. Do not over tighten too much, just snug is fine. Check to see that the bowl does not rock front to rear or side to side. That will break the wax ring seal. If it moves, you may need to shim it a bit to make it solid.  Strips of old vinyl flooring work well for this. Waterproof and durable.

Now caulk around the base of the toilet, leaving a small gap at the rear so you will notice any leaks in the future. Let it all set up and then install the tank and seat, hook up the supply and test.
Good Luck,

---------- FOLLOW-UP ----------


Thank you for the quick response.  On the existing tiolet I have removed there was NO wax ring, it appears the toilet was set in a wet mortar bed.  The outlet flange of the toilet as shown in the photo has the exact profile of the hardened mortar.
As far as installing a new toilet you are stating I need to remove the mortar layer, create a flat surface for the new toilet and install new anchor bolts into the concrete floor without installing a closet flange and then set the new toilet.  Please confirm I have this correct.  Thanks.

Yes.  Short of tearing up the concrete floor and installing a closet flange, you don't have a lot of options here. Working to a reasonably clean and flat surface and getting proper anchor bolts to hold in the concrete should handle this. One or more (if needed) wax rings should take care of the sealing.

Currently, clay pipe is not allowed to be installed under a slab or within the footprint of the house. If you do open the floor, there is no telling where the job would end.

It might be possible to break out enough concrete to mortar in a ring but I would not be very trusting of that to hold well.  It really depends on the condition of the concrete and its ability to hold any anchor bolts.  Always a tricky proposition when working on old houses.  Short of tearing out everything and starting over, it's always going to be a kludge job.
Good Luck,

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Dana Bostick


Pretty much any residential plumbing questions. For "item specific" details such as a specific model of fixture, I will need to research and there may not be any useful information available. Note: I live and work in Southern California. We do not, as a rule, use hot water or steam heating systems, oil fired boilers or private water wells so my knowledge in those areas is pretty limited. There are others here on AllExerts that can probably answer those questions better.


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