Any trick to keeping compression fittings from weeping?
I'm replacing the water supply-line valves in my bathroom (hot and cold to
the basin, cold to the toilet). The old ones were 38 years old and I wanted
to upgrade to the new 1/4 turn ballcock design. This is part of a total
The supply lines are 1/2 OD copper pipe and the valves attach to the copper
pipes with a compression fitting (brass sleeve between the valve body and
the compression nut).
Seemed straightforward, after removing the old valves I made sure the supply
lines were not out of round and were not galled. The ends of the pipes were
cut at 90 degrees as they should have been. I used fine steel wool to
remove any surface corrosion and to leave a smooth surface.
Wiped everything down well, installed the valves hand-tight (being careful
to not over-tighten) and turned the water back on.
Two out of the three valves weeped water around the compression fitting, I
could feel moisture where the pipe entered the compression nut. Not enough
to drip, but not a perfect seal. Tightened a little more by hand,
rechecked, and they were still weeping.
I finally removed all the valves, put on new compression sleeves, but this
time I smeared a thin coating of pipe thread compound (Harvey's TFE paste)
around the pipe before I put the compression sleeves on. Tightened
everything hand-tight as before, turned the water on, and no more weeping.
Dry as a bone.
Question: is it common for new compression fittings on old pipes to weep?
My solution worked but is there something else I should have done instead
What would a "regular" plumber have done? I might need to go through this
all again in another bath.
Thanks for your help.