lead (drain) pipe, drum trap questions

We have a bathtub that has a drum trap - which appears to be lead, as do the connecting pipes. (The stack is cast iron.) The trap is leaking.
I'm thinking to cut the lead pipe on the stack side of the trap, use a rubber coupling to join that end to PVC from there to the tub. Is there reason NOT to do this? The alternative would be to unsolder the lead pipe from the stack Y, and connect the PVC there. This looks like it would take big heat, and might never get clean enough for the new joint to seal well.
TIA, George
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buffalo ny: where is the leak? is this a job for epoxy? it is probably not a soft lead pipe. probably a horizontal galvanized drain pipe leak, feeding an iron or brass trap. if you change to pvc you will increase the noise of the drain. look at fernco rubber adapters for your task. there is no pressure only gravity on the tub drain. start the cutout after everybody's shower is done on a weekday business day morning, and take the thing to lowe's or your local plumbing supply shop like davis plumbing supply. exercise extreme caution, this type of activity leads to thoughts of remodeling the bathroom! :) -b see: http://www.fernco.com/
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On Mon, 17 Nov 2008 04:56:01 -0800 (PST), buffalobill

Near the top. The trap cover screws into a (brass?) threaded ring. I think this may be a separate piece, joined (soldered?) to the trap body, and the leak is at that joint. It's not easy to get a good look at it, and I could be misunderstanding things.

The situation is actually more complicated. The joists under the tub are kind of ... distressed. I think they need sistering, which would be easier with the pipes removed. AND, the last thing I want is to have to take the ceiling down again, should an epoxy-ish fix fail.

I could be wrong, but I think it's lead. All the metal is that dull grey color, and none of it is magnetic. The joints have significant build-up of solder. The pipes are curved, in a kind of 'hand-crafted' way. And, the trap wall is kind of flattened on one side.
G
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George wrote:

All lead tub drainage was common from turn of century till 1920's.
I would cut the lead close to the stack entrance and use a Mission-style coupling: http://www.fernco.com/plumbing/flexible-couplings/stock-couplings 1056 series coupling to adapt to PVC. If you can get to the stack connection, put the coupling over the solder thimble where the lead attaches; that will help prevent distortion of the lead. Sealant applied to the lead before sliding the coupling on will help avoid leaks.
Use a PVC P-trap, such as #78515: http://www.dafehr.com/Genova/gentrap.htm#P%20Trap%20with%20Solvent%20Weld%20Joint%20 (H%20x%20H)
There is one with a cleanout: #78415, but the CO may not be accessible.
If there is room, insert a CO TEE: #71315
Jim
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On Mon, 17 Nov 2008 08:13:07 -0500, Speedy Jim

That all makes sense, except it's so tight there. The (lead) pipes are bent to fit.
I see that Genova lists a PVC drum trap (75715). At first blush, that might simplify things. I gather that they're not recommended (and often not code), but would that be a really BAD idea?
And, re the PVC drum: could it be mounted upside down, so the cleanout was on the top? The current drum has an opening in the bathroom floor, which could make the cleanout accessible.
Thanks, G
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George wrote:

Yes, the PVC drum would make sense in your case and put the cleanout on top.
The guys bending lead to avoid obstructions had a big advantage, eh? :)
Use great care cutting the old lead so that you don't disturb it, possibly causing leaks elsewhere.
Jim
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drum traps are essentially obsolete and no longer used.
regular PVC traps can be easily snaked thru the tub control lever location.
you cant snake a drum trap, the snake just winds itself into a knot inside the drum.......
besides the top of the drum is just another leak spot.
do yourself a big favor, dont patch replace it ALL, unless you want to revisit this again,'
piping tends to all fail close in time, design life i guess.
add distrubing things just leads to sooner faliures
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replace drum trap with PVC, replace the part that fits on the tub too, brass is better there.
after repeatred problems over many years i had a plumber replace all the lines from tub and sink too basement.
the cast iron was clogged and rotting, and had a crack, what remained of copper was clogged, it was a mess, that damaged kitchen cieling below. our home was built in 1950
for me the plumber was a good choice i dont want to see that cieling cavatity again
the plumber managed to increase the slope of the sink drain, it emptys better
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sister joints with steel plates, like 1/2 inch thick.
takes up less space, and stronger too
anyone here ever open a drum trap top clean it out.
the plumber who replaced the entire line said even plumbers avoided distrurbing them for fear of leaks
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After reading these posts, I'm leaning toward replacing all the lead, right to the wye, rather than risk a future leak. (On further inspection, some of the soldering is ... 'curious-looking'.) But doing this has its own problems. So, I have to do some thinking, which doesn't go that quickly for me. Fortunately, we have a second shower.
Anyway, this has been very helpful, so thanks to all.
G
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repacing all the line is always best. old stuff is well old and more prone to fail.
a nice all new PVC line will likely outlive you.....
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