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jmbox80 · Aug 11, 2007, 07:45 PM

So we just bought a house and it seems that the joint where the 2nd floor bathroom toilet's PVC drain pipe is joined into the main cast-iron drain is leaking with a pretty constant drip. Needless to say, that doesn't do good things for the 1st floor bathroom's drywall ceiling. LOL. :rolleyes:

I've checked out a few other posted questions, and this "joining PVC to cast iron" topic seems to be a popular one. Now, the last plumber who was up there seemed to have been thinking along the same lines as you forum guys... There seems to be a Dual-Tite gasket squished in there between the PVC and the cast iron. BUT, water is leaking right under the gasket and drip-drip-dripping on out.

I noticed gasket wasn't driven in flush to the cast-iron when I started poking around. Should I just drive the thing back in there with a 'wedge'? The wedge isn't something special is it? Should I silicone caulk around the gasket? I'm afraid it'll still leak if I simply drive it in with no caulk.

Any clues on how I can remedy this would be really appreciated!

Thanks!

+josh

MOWERMAN2468 · Aug 11, 2007, 08:45 PM

Well if you are referring to a plastic mounting toilet flange hooking to a cast iron pipe and then going down, you could.

Remove the toilet,
Remove the toilet flange,
Place a rubber boot, ( a rubber cylinder shaped boot open on both ends)
Tighten the clamps and should stop the leak.
Of course you have to be able to reach this area to do this.

MOWERMAN2468 · Aug 11, 2007, 10:55 PM

It makes perfect sense. Place a rubber boot around the two pieces and stop the dang leak.

scirocco70 · Aug 12, 2007, 07:16 AM

It sounds like you've got a "closet bend" (the part the toilet connects to) in PVC which is connected to the bell-end of old-style bell-and-spigot cast iron using one of the "donuts" that replace a traditional oakum and lead seal.

You could try repacking the seal, though this may indeed make it leak more. I've seen advice here about lubricating the seal before driving it, I myself would be tempted to use a little (not enough to squeeze into the pipe!) RTV silicone, as it'll be a lube first then a sealant. Particularly on older, pitted and non-smooth cast iron.

A substance I HAVE used as a sealant on older cast iron is roofing/flashing tar. This conveniently comes in tubes for a caulking gun, and the better grades never really dry out and are pretty thick.

Anyhow, if you can't get the leak to stop, here's what you do..

1) Search for a old post by me about cutting cast iron. Search on "cast iron" and "diamond" There are some pictures which may be helpful.

2) Get a "no-hub" connector of the right size. This is a neoprene (not rubber, but similar) and stainless steel clamp/boot arrangement. Some are made by Fernco but there are other brands too. Link: Fernco, Inc.

3) Get a new closet bend, a butt connector and a short piece of PVC pipe, and replace the leaky bell/spigot joint altogether. Do this by cutting the cast iron just behind (or more, as convenient to access) the bell.

4) Do NOT forget to support the cast iron pipe near the cut! Assuming this is a horizontal pipe, you probably want a split-ring hanger. Here's a link:
Grainger Industrial Supply
This one has a picture of a complete hanger: Plumbing

Good luck!

~aaron

speedball1 · Aug 12, 2007, 07:23 AM

What Mowerman fails to realize is that this isn't the case of two bald pieces of pipe joined by a No-hub Clamp that you can place a rubber boot over but a hub with a Duel-Tite neoprene gasket that the PVC pipe has been inserted into. Since Duel-Tite Gaskets were meant to join cast iron pipes and PVC's thicker then cast iron the PVC has to be beveled and the ridges in the gasket have to be shaved down to allow the PVC to slip into the gasket. Add all this up plus the fact that the gasket wasn't seated correctly almost guarantees a leak in time especially if the PVC's cocked a little.
Several options come to mind. You may break the connection and install it again or wrap the hub and joint with Stop-Leak tape or cut off the hub and connect the two bald pieces with a Fernco Shielded Coupling or a No-Hub Band. Good luck in whatever you decxide. Tom

jmbox80 · Aug 12, 2007, 09:40 PM

The one thing I didn't realize in reading all the previous posts was that the Dual-Tite was meant to join a PVC that was > or = to the thickness of the cast iron it was being joined with. Mine isn't. The PVC diameter is actually smaller and it slips inside the cast iron. So maybe this ISN'T a Dual-Tite gasket?

Since a picture is worth 1000 words, here goes: