"Allen McCann" wrote in message
...
Is a"gate valve" the same as the outdoor faucet on most homes? If so what
is the problem with them?

Allen

Doug Dotson wrote:

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


Answer is yes. You turn the round handle and this screws down a gate across
the diameter of the pipe, sort of like a guillotine.

There are several potential problems with them and I'll just mention a
couple:

-not really intended for marine use so you don't know the type of alloy used
-the attachment to the hull is a weak point and they can be broken off
-you cannot easily tell if the valve is open or closed by looking at it
-they tend to seize up if you don't exercise them frequently and people
don't tend to do this because it is a pain to turn the valve a dozen time to
close/open it

Lots of older boats have them. If you maintain them you can live with them
but lots of folks replace them with proper seacocks.