Leaks in lead joints

Hey, folks... my apologies if this topic was addressed elsewhere; I searched & wasn't able to find anything.

The story: I'm adding a 2nd bathroom. I've cut into part of the existing C.I. stack and replaced with PVC to accomodate the new DWV... the main floor toilet is still C.I.
I set up a pressure-test & found that I'm leaking air at one of the hubs; appears that the lead joint isn't as tight as it should be. I tried tightening it up by tamping the lead joint down with a hammer and a small bolt, but no dice. I found the correct Fernco donut for the XH cast, so I'm planning on digging the lead/oakum out of this hub-joint and repairing it that way.

BUT... now I find myself looking at all of the other hubs on the remaining cast, and thinking that there's a heckuva lot of potential for more leaks sometime in the future.
Is there a way to seal existing lead joints without replacing them? Any kind of sealant that could be applied over the existing lead to stop smaller leaks?
There wasn't any problem with leaks prior to this, just when 5 lbs. of air pressure is applied.

(Realistically, I know that the most responsible thing for me to do would be to tear out all of the remaining CI and replace it all with plastic. And I might go that route, but I'm hoping there's a quick fix that might get me by for the time being... my wife's losing patience with the job!)

thanks in advance for any help with this!
E.

Sometimes the lead joint did not have the oakum packed in correctly, it is the oakum that makes the seal the lead is there to hold the oakum in place. I have ran across this when we use a reciprocating saw to cut the pipe, seems the vibration loosened up the joint, 9 times out of 10 I was able to use my caulking irons to tighten it back down.

SewerRatz said:

9 times out of 10 I was able to use my caulking irons to tighten it back down.

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...so, what do you do on that 10th time?

I remove the lead and the old oakum and pack in fresh oakum and pour the joint.

Yeah, that's what I was afraid of. Just had to hear it from a pro to know for sure, I guess.

thanks for the help, pal... much appreciated!

Sorry I couldn't be more helpful. I do hope it all works out for you in the end.

Don't air test

Lead joints are not designed to be air tight they are designed to be water tight. Once the oakum gets water against it it will swell and seal the joint, the lead keeps it in place. Chances are your existing lead joint is just fine. the cast iron institute, spokespeople for the cast iron pipe industry, will tell you the same thing. Lead joint systems were tested with a 10 foot column of water, not compressed air.

Yep, near to impossible to do an air test on B&S.

joint

Lead joints were not supposed to be sealed with a hammer and a bolt. A proper set of caulking irons should do the job.

hj said:

Lead joints were not supposed to be sealed with a hammer and a bolt. A proper set of caulking irons should do the job.

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yeah... no argument here. I've made a lot of dumb, rookie-mistakes through this process, and skimping on the proper tools is no exception.
I'm learning, though! (...i hope...)

Ask if you can use a standing water column leak test instead. If he's young, he may not understand the subtle differences in the systems.

jadnashua said:

Ask if you can use a standing water column leak test instead. If he's young, he may not understand the subtle differences in the systems.

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Thats what we do for most commercial applications here. 5 feet of standing water in a 4" pipe does the trick.

test

I could regale you with the process we went through, many years ago, to reactivate a water main system installed before the Great Depression, and then abandoned until the 50's. The city required a pressure test before they would certify it, but after all those years there was no way the leak/oakum joints were going to be "air tight". We went through many gyrations, and a couple of comedy of errors, before they were satisfied.