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Seacock/Gate Valves

I need to replace some gate valves in our boat and I was looking at Apollo Ball valves. They say that they will work with thru-the-hulls. Since thru-the-hulls have straight pipe threads and the ball valves have tapered pipe threads I don't see how this is possible. Am I missing something? I know that seacocks have both straight and tapered threads but a seacock would probably be overkill in this case.
James
May 10
Who is "they"? Chuck
May 10
There are ball valves that have tapered threads and seacock ball valves that have straight threads. Apollo and Groco seacocks have NTP (tapered) top thread and the bottom thread is NPS (straight). krj
May 10
@news.earthlink.net:

> > Yes, to the left.

Larry

Larry
May 10
And you can probably bet that at least the Grocos are made with the right type of bronze, not true with the hardware store variety which is actuall brass (copper and zinc) vs naval bronze which is primarily copper and tin. The issue with brass is that the zinc will disappear over time due to electrolytic action. Wayne.B
May 10
This is one of those things...

The theoretical reasons for not putting a tapered thread ball valve on a straight thread through hull are absolute and irrefutable. All the strain is on just one or two threads. The stress is nearly infinite. The electrical connections is through a very small amount of metal. It will sink your boat. No question.

The practical experience and track record of doing this is also absolute and irrefutable. It's been done for years. I've never heard of a boat sinking because of it. The just retired yard guy I talked it over with a couple years ago had been doing it for over 20 years without a problem.

A proper seacock is always better but I have a ball valve threaded onto an old through hull in my boat. The through hull was rock solid and it was in a place where nothing heavy could fall against it. The threads just deform a small amount and pipe sealant does the rest. I would use a stick type compound that will harden in this case instead of Teflon tape.

Roger
May 10
   

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