I found a brass coupling that has a rubber washer on the inside of the cylinder. As you tighten the two pieces of the coupling together I guess it compresses the rubber washer around the lead pipe to make the seal. Do you know if there is some kind of sealant that I could put near the rubber washer (around the lead pipe) to make a tighter seal. I would really like to make sure that this part of the connection is sealed as tight as possible. Optimally something that doesn't eat away at the rubber washer. Thank you so much for all of your assistance. I has been so helpful. Good luck to you.