On Saturday, March 18, 2017 at 8:22:19 AM UTC-4, Joe Mayer wrote:
I have 120psi water pressure at my house and am having a hard time
getting a complete seal on the water connections of my tub faucet.
I had to use a couple of brass adapters to go from a 1/2" copper line to a
3/4" brass connection, so I have more joints than usual. I am using teflon
tape on all the joints and keep getting a little seepage around the joints.
The previous connections on the old faucet with 1/2" connectors were what I
think are called slip joints, using cone-shaped rubber washer. The brass
fittings do not have any kind of compression joint or washer to seal off the
water, except on the end that connects to the copper line, where a
compression ring seems to be sealing just fine. The other connections
depend on the sealant on the threads. Should I be using permanent pipe
sealer at the threads that do not connect directly to the faucet and the
water line? Or is there something better than teflon tape that I should
use on the joints? I am wrapping about 2 layers of the teflon tape around
the male connectors, starting at the first threads of each joint.

Most household fixtures are not rated for120 PSI. Besides havering trouble with your
fittings, I'm surprised that you aren't damaging your fixtures.

Have you considered a Pressure Reducing Valve to bring the pressure down to something
reasonable, like 60 PSI?