Just bought a house with damaged toilet. Existing plumbing is pvc toilet flange inserted into cast iron drain line. The flange is loose and needs to be refastened to the floor, subfloor condition permitting . How do I seal the pvc toilet flange to cast iron drain pipe to ensure no sewer gas leak?

Hi Newowner...

You want to purchase a TWIST AND SET closet flange... see picture... and a small container of silicone grease. Here, grease the neoprene sleeve a bit and then twist this flange down and into proper placement. Then confirm that the toilet bolts line up right and secure the flange to the floor. That should get you up and running again.

You could also purchase a flange that has 3 screws that when screwed pull up and expand the neoprene seal against the wall of the pipe... see other picture.

Both types should be available at home depot, Lowe's or menards... ;)

Let me know if you have more questions here...

MARK