Tub only leaks when the water is let out of the tub. Like a small waterfall into the ceiling below. The pipes are lead... This does not happen when the shower is used.. Thoughts?

Is the shower a separate unit than the tub, like a stall? I am 64 years old and never saw a lead drain pipe but I know they did exist in the 20s and earlier. Are you sure that's what you have? This may be what you need http://www.us.kohler.com/onlinecatalog/pdf/105266_2.pdf

The flow through a shower head is much less than the flow of a tub being drained... the corrosion and leak is likely on the TOP side of the pipe.

Where are you located... how old is the building... they will help us guess what you might have.

Located in pa. Home was built in 1940. A plumber looked at the pipes and told me they were lead and I would probably need to replace all the lead drain pipes from the toilet, sink and bath/shower combo.

For that type of work you always want to get 3 bids from licensed plumbing contractors. Sounds fishy if you ask me.

Never heard of lead pipes being used as late as 1940 in the USA.. they might be copper or cast iron. Most likely Cast Iron as copper was scarce for the war effor back then. I've actually seen lead pipes in use post WW2 but that was in Italy.

I agree, not heard of lead used later than the 20s. However, there wasn't much metal shortage in 1940, we were still selling tons of it to Japan and look what they built. In 1940 we embargoed selling metal to Japan and actually had a suplus of metal for the time. By 1942 we started building a lot more war materials.

I am 64 years old and never saw a lead drain pipe And I'm 85 and back when I was breaking into the trade I've seen plenty. In fact, one of the test requirements was to wipe a lead joint. We use cast iron in our new construction in the 40's so Smoothy makes a valid point. However, it's tough for me to swallow that a experienced plumber could mistake any other pipe as a lead pipe.
Bottom line!
If the closet bend is, indeed, lead along with the rest of the drainage it should all be replaced. Chances are the tub also has a drum trap that also should be replaced. As Bob advised, get three estimates and go with the one you're most comfortable with. Good luck, Tom