How to fix this leaky old bathroom drain trap?

[AerixJ]

We returned from a family vacation to find water leaking from the upstairs bathroom all the way down into the basement (and all over my tools!). I was able to get access to the problem area through a built-in cabinet in the dining room and found the problem:

The drain pipe coming from the drain trap is leaking right where it's welded onto the trap. This is an old house -- built in the 20s. The pipe is not fitted onto the trap (unless it's under the weld material?), but appears welded on with what looks like lead. Here's a closeup:

What can I do to fix this leak? It's pretty bad -- you can actually move the pipe a bit where it is supposed to be attached to the trap. I've considered using a patching product called Waterweld, which I've used with luck on steam pipes and such. But this is a pretty big area and a joint to boot.

I'd really appreciate some insight on this. Even if I have to call in a pro, it's helpful to know what I'm dealing with. Thanks.

 

[Mikey]

My guess is that it's a lead trap, with the arms soldered to the trap body. The whole affair should have been slightly flexible, but apparently after 80 years whatever caused the arm to flex relative to the body finally was too much for it. That supporting board looks to have bent over the years.

How are your soldering skills? I'll let an experienced old pro continue with the details, but I'll bet it's repairable, although you'd probably be better off replacing this with a proper modern trap setup. God (or the aforementioned pro) knows how you'd do that.

 

[Sponsor]

 

[Jadnashua]

Does the shower drain well? It looks like things have to go uphill to get out of that contraption. I'll bet it is full of hair, and nasty scum.

are the shower and sink individually trapped?

Looks like you could cut the drain pipe near there (the cast iron) and patch in a proper, legal connection, but you might need to add traps to the sink and shower if they don't exist.

That might be an old drum trap, which are no longer legal, and didn't work that great when they were.

One of the pros will have some thoughts if you wait...

 

[AerixJ]

Fixed the leak for now, but still curious about the best repair . . .

I did some research at the library and ascertained that the join there on the drum trap is indeed lead, using the old "lead wipe" method for joining cast iron pipes. So this wouldn't be a soldering repair, but a matter of cooking up some lead and pouring it on there -- not really doable in that location.

I used plumbers epoxy putty to repair the connection between the drain pipe and the drum trap, applying the material both inside the trap and outside on the pipe. So far so good.

As for the shower and sink, the shower does not have its own trap, but does drain very well. (And it's only the camera angle that makes it look like an uphill climb from the shower; it does flow downhill actually.) The sink does have its own trap -- it's the original sink, a pedestal unit that isn't even attached to either the floor or the wall.

At some point down the road this will all have to be redone, so even though I've fixed the immediate problem, I'd love to see more comments on what I've got going on here and what I could do about updating it. My biggest question is how to go from cast iron to PVC (if that's what's advisable).