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This is a reply to Gate Valve removal
Been there, done that...
Submitted by Chris Burti of Washington NC on 03/09 at 06:21AM
I did it in the water on my 30-year old Cal's OEM 1-1/4" head
discharge a couple of years ago. I had no problems but proceeded with
much caution and a certain amount of trepidation.
I'm going to set out my procedure as if you are a novice, but I am
definitely not assuming that you actually are one. Some folks that
may be tempted to try this procedure may be.
First, I used kerosene liberally overnight to soak all of the threads
inside and out (it is the 'active' ingrdient of many rust solvents).
I also made arrangements with the yard for an emergency haulout if
things went sour.
I had an emergency bung ready, all parts prepared, batteries charged,
pumps ready and crossed my fingers.
It is very important that your new valve does not have tapered pipe
threads. Through hulls have British straight threads and a pipe valve
will not seal without undue pressure...and even then, you will only
have about three threads engaged, making a very vulnerable joint.
I installed about two feet of hose on the inboard side of the valve
and opened it fully. I then snugged down the nut on the throuh hull
fitting (and was surprised to find that it would actually tighten a
little). As others have noted, you will want to be very careful not
to turn the body of the through hull.
Leave a wrench on the nut when removing and replacing valves in order
to help prevent the through hull from turning and to keep from
damaging the threads by putting a wrench on the body of the through
hull fitting. I was able to wedge that wrench against a bulkhead,
freeing both hands.
Next, is a trick that I learned in my youth while working with a
Tighten...yes...tighten...the old valve with a smart rap of a hammer
on the end of the handle of the wrench. This is the most effective
way of loosening an old thread that I have ever learned. You will
likely need to reverse the wrench on the nut if you are using a pipe
wrench. The old valve should now come off easily.
As you get near the end of the threads, water will start coming in
with increasing pressure. Don't panic...it is far less volume than it
would appear. When the old valve comes free, pop the bung in the
through hull and take a deep breath.
Reverse the wrench on the through hull nut again and ready the new
valve. The purpose of the hose and open valve is to reduce water
pressure while threading on the new valve. The hose should extend
above the water line. As soon as the valve and fitting make contact,
very little force is required to keep the leaking down to a minimum.
This allows you to thread on the valve easily without cross-threading.
When the valve is screwed down all the way, it doesn't require a lot
of torque to fully tighten it...so don't overdo it.
I doubt that I took on more than a half a gallon of water in the
process and have had no problems since.