I have a 3" pvc pipe originally roughed into the concrete floor. It was cut off flush to the floor to insert the flange. I inserted an Oatey twist n set flange tightly and it sits flat on the concrete. I set a simple wax ring on the toilet horn and set the toilet onto the flange. It leaks after 5 flushes and 5 minutes. I tried multiple wax rings w and without plastic seals built into the rings. I had slightly better luck with a flat, wax-free gasket that leaked after 20 flushes and 20 minutes. Since this Oatey Flange fits INTO the 3 inch pipe, this makes the inside of the flange opening less than 3 inches. I think this is the root of the problem. A typical 3 inch flange has an inside taper which the twist n set does not.

Am I to now chip away the concrete and glue a true 3" flange onto the outside of the 3 inch pipe and mount it flat on the floor so the true 3" flange will take the wax ring correctly or is there a product that allows the twist n set to seal on the toilet horn without leaking?

Not all Twist-n-sets are alike. Twist N Set Cast Iron Replacement Closet Flange :: Oatey.com Did you use the one made for a 3" PVC pipe. I seriously doubt that you leak is the seal between the flange and the pipe, not unless water starts running up hill. Did you use jonnie bolts into the concrete to hold the flang and then the proper brass toilet mounting bolts?

I used the PVC Oatey Twist n set with the black rubber gasket that pulls up to the top when you twist the flange into the inside of the 3 inch pipe. I used 2 3/4" tapcons to mount it into the concrete and it is solid enough to hold everything without rocking or moving when the closet bolts are tightened.

That description fitting them all, they all have the black neoprne collar. Get a good quality wax ring with its own neoprene collar. Put it on the toilet, not the floor and then lower the toilet over the brass bolts. Put your entire weight on the toilet, sit on it if you have to. Tighten the bolts very snug but don't over tighten, they hold in place but are made to pull the toilet down. Hour later, sit on it again and retighten.

Thank you for the reply. I have tried at least 3 standard wax rings with no collar. I have tried a jumbo and a standard kan't leak with the collars. The collars deform when the toilet is set because the inside diameter of the twist n set hole is smaller than 3 inches and is flat at the top area of the entrance to the hole instead of tapered. The flat part of the entrance into the flange is too small to receive the collar. Setting the toilet should be a no brainer and should go together with a smooth mush and tighten and go home. But the rings do not appear to be working. I think the lack of a tapered downward receiver in the top of this twist n set 3 inch flange that inserts inside of the 3 inch pipe is causing the problem. I do not believe water is flowing from the bottom upward around the flange. I think there is not enough space between the flange and the wax ring when it is set because of the flat areaa on top of the twist n set. A true 3 inch flange has a tapered receiver insteead of a narrow flat one. I hope I described it better.

The Twist-n-set is not your problem. I don't know anyone here who has ever thought they were defective or not top notch. If you flange siit on top of the floor there is great contact between the floor, ring and toilet. I am strating to wonder are all 5 of those flushes you do totally the same and totally complete, no slowing down of the drainage?

I poured 2 gal of water straight down the drain and it disappeared immediately as a test.

But 5 flushes later you had a leak, right? Try running about 8 buckets down the toilet or get at least two 5 gallon buckets and dump fairly fast. It should all drain almost immediately with not hesitation.

I will test that. The main discharge line in the house is only 6 feet away from this flange. When the other appliances are flushed or dishwasher drains you can hear the activity but no waste water comes up out of the flange. I have a plastic cup sealing the hole and no leaks otherwise. Thank you for your advice.

The toilet hole? I'd go with a damp towel, the cup can pop up if the sewer burps.

I know this is a dumb question, but,, have you checked other areas of toilet for leakage? You may have a leak between the tank and bowl that runs down the backside of the bowl and spreads out around bottom of bowl. A bad tank gasket would cause a leak only when flushed.

Turned out to be a flaw in the underside of the toilet. Apparently when the unit was taken out of the mold it was pulled pushed and the porcelain tore before the unit was baked in the kiln. There was a hairline tear, not a crack along the p trap up inside the front part of the bowl area. You could only see it with the unit upside down with a spotlight on the tear. I boought a new unit and it seated with no leaks just like it was supposed to. I had a plumber come out to help me and we put in a different flange. I set the new toilet myself. What an experience!

Ohh, fualty toilet from the factory can be a real pain. Just glad you got er figured out. Good job. Take care