I'm tired of patching 35+ yo galvanized pipe in my house but am on a very limited (fixed income) budget.
I'm planning on replacing all horizontal galvanized runs with 3/4" CPVC all the way to all 1/2'' galvanized vertical drops to kitchen, baths, etc. I'm able to get transition ADAPTERs (brass FIP or stainless MIP or FIP threads) or transition UNIONs w/brass FIP (only)threads. If I use adapters w/SS MIP threads I can go directly into 1/2" 90 els; if I use unions w/FIP threads, I must install a (hex) nipple in each el for the union FIP thread.
I understand unions can handle thermal expansion differences between metal/plastic w/their rubber gasket but the adapter plastic/metal "halves" are bonded together and can be tightened down metal-to-metal w/no rubber gasket; will that also work? Can I use adapters instead of unions for transitioning? Including water heater? Is there any consensus on stainless vs. brass threads on the adapters should those be recommended?
What's the easiest way to remove old putty and debris from the FIP threads in the galvanized 90 els? Should I just replace the 1/2" els? Some will be extremely hard to remove but easy to tie into.
Single story house, simple layout.
I plan on using teflon tape exclusively but is tape needed on unions?
6 of one, 1/2 dozen of the other on all that stuff. If you ever plan on replacing the drop pipes you're gonna have to either cut off or unthread the stuff anyway.
For your question on the union, no you don't need teflon tape on the union nut itself. On the connecting ends however, you do need teflon tape on whatever is threading into the union.
Bit of advice - get enough stuff to replace the risers as well. If you're having problems with leaks, and patching the stuff already, if you unthread something, you're likely to have at least one problem with old threads.
Remember, CPVC needs to be supported every 4 feet.