Hi All – I just posted recently seeking advice on a leaky sink-drain seacock I discovered on my Catalina 30. The yard pulled the boat and its been sitting on the hard for a week…I am thinking they may not get to this one by the weekend so I should just replace the thing myself and save some money in doing so. What is the best way to go about this? I want to replace with a bronze thru-hull and bronze ball valve. There is no wood backing plate on the hull right now….looks like that may be the culprit for the leak. What is the best type of wood I should use? Should I saturate the wood backing-plate in glass-resin and then use 5200 on the thru-hull and backing plate to hold / seal everything? Thanks – appreciate the advice here. Rob
Thru-Hull and Seacock Replacement
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Pipe threads & thru-hulls
I'm not a plumber, but I believe that the designation NPS indicates a straight, non-tapered thread. The "normal" thread used on plumbing fittings is designated NPT , the 'T' meaning tapered. The two are not compatable and will not make a reliable joint, but if the thru-hull is a standard NPS thread and the ball valve is also NPS of the same diameter, they should mate OK, no?
I'm not a plumber, but I believe that the designation NPS indicates a straight, non-tapered thread. The "normal" thread used on plumbing fittings is designated NPT , the 'T' meaning tapered. The two are not compatable and will not make a reliable joint, but if the thru-hull is a standard NPS thread and the ball valve is also NPS of the same diameter, they should mate OK, no?
Striaght threads
Straight threads and straight threads need a compression or flare type of fit to keep water out or in the case of a sea cock a flanged base slathered with 4200 or similar. NPS (straight thread)is used on flared or compression plumbing fittings and NPT (tapered) threads are used for a water tight thread to thread fitting with teflon tape and/or pipe dope. Think of straight threads like threading a nut and bolt together. What would keep the water out or what would keep it tight or from spinning every time you turned the BV handle? As far as I know, and I have searched, no one makes a through hull, without a flange, that is NPT (tapred) threaded... Using an NPT BV with an NPS through hull is dangerous and so is using an NPS through hull with an NPS BV because there is no pressure fit. Many, many insurance companies are now requiring proper sea cocks and not a BV on a through hull with mis-matched threads...
Straight threads and straight threads need a compression or flare type of fit to keep water out or in the case of a sea cock a flanged base slathered with 4200 or similar. NPS (straight thread)is used on flared or compression plumbing fittings and NPT (tapered) threads are used for a water tight thread to thread fitting with teflon tape and/or pipe dope. Think of straight threads like threading a nut and bolt together. What would keep the water out or what would keep it tight or from spinning every time you turned the BV handle? As far as I know, and I have searched, no one makes a through hull, without a flange, that is NPT (tapred) threaded... Using an NPT BV with an NPS through hull is dangerous and so is using an NPS through hull with an NPS BV because there is no pressure fit. Many, many insurance companies are now requiring proper sea cocks and not a BV on a through hull with mis-matched threads...
Because..
With the Groco flanged adapter plate you can very easily replace the part that always goes bad. The valve! I also use the flanged adapters in areas where I don't have the height and need a 90 degree valve of which no one makes a sea cock that is 90 that I know of. I did use three Groco flanged sea cocks, where I had the vertical space in the head under the sink, and then three flanged adapters with Groco BV's in areas where height was a restriction.
With the Groco flanged adapter plate you can very easily replace the part that always goes bad. The valve! I also use the flanged adapters in areas where I don't have the height and need a 90 degree valve of which no one makes a sea cock that is 90 that I know of. I did use three Groco flanged sea cocks, where I had the vertical space in the head under the sink, and then three flanged adapters with Groco BV's in areas where height was a restriction.
Maine Sail. I know you are sticking with Bronze
But Forespar makes Marelon "Seacocks" with a 90 degree valve. See page 12 of the link I had below
But Forespar makes Marelon "Seacocks" with a 90 degree valve. See page 12 of the link I had below
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