Why not just do it the right way? NPS thruhull to NPS valve.

Doug

"Roger Long" wrote in message
...
Calder and other authorities are dead set against putting NPT ball valves
on NPS through hull fittings as is often done when replacing gate valves.
The geometry of the thread engagement gives me the willies as well because
all the load is on just one or two threads due to the taper.

My boatyard tells me that they do it all the time however as does everyone
else. The gate valves on my 1980 boat haven't broken off yet either. I
just threaded a one half inch ball valve and through hull together and it
doesn't look or feel as bad as the theory.

Except for a couple of above waterline drains, the seacocks I'm going to
put in will be flanged and bolted. I'm just curious though, has anyone
ever heard of a NPT valve on a NPS through hull breaking off or leaking?

--

Roger Long