[Public-List] Cockpit Drain Seacocks

[Don Lang]

Another important consideration is that thru-hulls have straight thread and ball valves have tapered pipe thread.
A ball valve screwed directly on to a thru-hull will have at best, three threads engaged, typically just two.
Groco does make an adapter flange that is installed between the thru-hull and ball valves for retro fitting vessels without the need for discarding existing ball valves (if they are serviceable) and at considerably less expense than a seacock.  Picture of one here on my blog:  http://alberg30.blogspot.com/2008/12/thru-hulls.html

In regards too water in the ball freezing and causing damage; we have seen this on three vessels here over the years (fresh water boats, one sunk as a result), it seems to be more predominant with the larger valves above 2" but one was a 1.5" valve.
If there is not a drain screw one can pour some anti-freeze down the hose into the valve and close it while pouring capturing some of the anti-freeze in the ball. A preferred method (more environmentally sound) is to blow compressed air through the hose clearing the ball valve of water and then closing it while the air is flowing through it. We use a rubber "cup" from a set of outboard engine "flush muffs"  and can accomodate any hose size with it.


Cheers, Don   #473 



      
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