[Duane 70]

What is the proper thread sealant to use for the threaded connections when connecting different types of water pipe materials (i.e. copper to brass, galvanized to brass, galvanized to copper, etc.), pipe dope or teflon tape? I know that tape is used for CPVC but I'm not sure which is best for metals. Thanks for your help.

[majakdragon]

The term "thread sealant" is rather confusing. Pipe dope and teflon tape are thread lubricants. Pipe threads are tapered. If you lay a piece of threaded pipe on a flat surface, you can see this. When piping is screwed together, the taper "seats" and the joint is sealed. Lubricants insure that the joint is properly seated. I use teflon tape on most piping except gas. I prefer a joint compound such as Rector Seal for this type piping. When changing materials such as copper to steel, a dielectric union is warranted to prevent electrolosis which will cause failure more quickly.

[downunder]

I asked this same question recently while picking up some supplies at the local plumbing shop. I do general maintenance work, some plumbing, some electrical, carpentry, etc. for a local parks department.
When I asked the question about the proper sealant for different materials, i.e. PVC coupled with iron pipe, five different contractors, in the same breath, said "Blue Blocker." I think it is a dollar or two more but generally the same price as the yellow.

I figured if all of them gave the same answer at the same time, and they do it every day, I went with their advice.