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Don Flowers
seacock or gatevalve
I would use a seacock versus a gatevalve on my vessel if those were my two choices. I have always heard that gate valves tend to leak after use. Although, it is a good question. I think one of the problems with a gate valve is that when the wall is lowered in the grooved seal area junk can be in that groove and not allow for complete closure. If you are looking for options other than a seacock I have also used stainless steel ball valves with great success; they (ball valves) don't tend to freeze in position such as seacocks often do when not rotated or serviced often.The stainless ball(in a ball valve) rotates inside a silicone seal which resists sticking. Hope I helped.
I would use a seacock versus a gatevalve on my vessel if those were my two choices. I have always heard that gate valves tend to leak after use. Although, it is a good question. I think one of the problems with a gate valve is that when the wall is lowered in the grooved seal area junk can be in that groove and not allow for complete closure. If you are looking for options other than a seacock I have also used stainless steel ball valves with great success; they (ball valves) don't tend to freeze in position such as seacocks often do when not rotated or serviced often.The stainless ball(in a ball valve) rotates inside a silicone seal which resists sticking. Hope I helped.
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Tom Ehmke
Ball valve was OEM on my Oday 272
I replaced it last week after I discovered that the side had split (apparently from water freezing inside the valve) before last season. I had noticed that when I rotated the handle to open or close it, it would leak in the open position... so I kept it closed during last season. The one I replaced it with has a plug in the bottom to allow for end of season drainage before winter. As an aside to your question, the valve operated my overboard holding tank discharge which is illegal on Lake Erie. I should have gone the cheap route and bought a female plug rather than the new valve as I decided not to reconnect the hose which was there for overboard discharge. I was fixated on keeping the boat in its original condition and not really thinking of the need for the valve until a friend reminded me that I spent a lot of money for something I don't intend to use. Tom
I replaced it last week after I discovered that the side had split (apparently from water freezing inside the valve) before last season. I had noticed that when I rotated the handle to open or close it, it would leak in the open position... so I kept it closed during last season. The one I replaced it with has a plug in the bottom to allow for end of season drainage before winter. As an aside to your question, the valve operated my overboard holding tank discharge which is illegal on Lake Erie. I should have gone the cheap route and bought a female plug rather than the new valve as I decided not to reconnect the hose which was there for overboard discharge. I was fixated on keeping the boat in its original condition and not really thinking of the need for the valve until a friend reminded me that I spent a lot of money for something I don't intend to use. Tom
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Scott
Gate valves and ball valves vs seacocks
Gates and Balls mostly all have tapered threads which do not mesh with the straight threads on the through-hull fittings. I was amazed at how many 'professionals' I spoke with who didn't think that mattered and suggested that it was no big deal. Try screwing a tapered (NPT) valve on your below the waterline through Hull with its NPS threads and you'll find it will only go about a turn and half before it jams. This means you have about 2-3 threads, only one of which is really meshed between you and a new submarine. My 85 H-34 had gates on it and everything I've read from Calder to this site to the ABYC unanimously warned that 'gate valves sink sailboats. Period. I replaced them all this past weekend with Conbraco Seacocks --even the one that discharges the holding tank that I'll never use. Check the archives on this site there is a wealth of experience here.
Gates and Balls mostly all have tapered threads which do not mesh with the straight threads on the through-hull fittings. I was amazed at how many 'professionals' I spoke with who didn't think that mattered and suggested that it was no big deal. Try screwing a tapered (NPT) valve on your below the waterline through Hull with its NPS threads and you'll find it will only go about a turn and half before it jams. This means you have about 2-3 threads, only one of which is really meshed between you and a new submarine. My 85 H-34 had gates on it and everything I've read from Calder to this site to the ABYC unanimously warned that 'gate valves sink sailboats. Period. I replaced them all this past weekend with Conbraco Seacocks --even the one that discharges the holding tank that I'll never use. Check the archives on this site there is a wealth of experience here.
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Tim
valves
Seacock: http://members.cox.net/building.galene/Images/TagSale/ThruHull.jpg Note the bolts holes for attaching to the hull and the large handle for opening and closing. The pressure from the handle is against the bolts not the thread stem of the through hull. Ball valve: http://www.rittenhouse.ca/images/products/commercial/big/bvalve2.jpg Note the large handle. Gate valve: http://www.sabrebright.com/gate%20valve.jpg Note the rotary action to close. The chief problem is the lack of a positive closing mechanism combined with an easily jammed gate that slides across the pipe opening. http://www.mymcad.com/Gate-Valve.gif
Seacock: http://members.cox.net/building.galene/Images/TagSale/ThruHull.jpg Note the bolts holes for attaching to the hull and the large handle for opening and closing. The pressure from the handle is against the bolts not the thread stem of the through hull. Ball valve: http://www.rittenhouse.ca/images/products/commercial/big/bvalve2.jpg Note the large handle. Gate valve: http://www.sabrebright.com/gate%20valve.jpg Note the rotary action to close. The chief problem is the lack of a positive closing mechanism combined with an easily jammed gate that slides across the pipe opening. http://www.mymcad.com/Gate-Valve.gif
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MArk
The problem with gates
The problem with gate valves is that their failure mode is catasrophic. What I mean is, it could work perfectly for years then, one day the handle turns, the shaft travels down, but where the gate plates attach to the shaft has corroded away. The shaft goes down but the gate stays up so the valve stays open even though looking at the shaft, it should be closed. Ball valves and seacocks (which are usually flanged) will fail eventually also. Their failure mode is to develop progressively larger leaks over long periods of time. This is much easier to spot and less critical than the internal failure of a gate valve. (See link below) Happy (fusion powered) sails *_/), MArk
The problem with gate valves is that their failure mode is catasrophic. What I mean is, it could work perfectly for years then, one day the handle turns, the shaft travels down, but where the gate plates attach to the shaft has corroded away. The shaft goes down but the gate stays up so the valve stays open even though looking at the shaft, it should be closed. Ball valves and seacocks (which are usually flanged) will fail eventually also. Their failure mode is to develop progressively larger leaks over long periods of time. This is much easier to spot and less critical than the internal failure of a gate valve. (See link below) Happy (fusion powered) sails *_/), MArk
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Debra B
always use seacocks or at least ball valves
you won't be disappointed. They can fail; I had 2 that were just not working - they have been replaced. But both gate valves were frozen.
you won't be disappointed. They can fail; I had 2 that were just not working - they have been replaced. But both gate valves were frozen.
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Dale I
Time & $$
The previous owner of my vessel has the replaced the gate valves with ball valves onto the original thru-hulls. While on the dry this past year I contemplated the replacement of the entire units. This would have involved not only the replacement of $30 balls and $40 thru-hulls with $85-95 seacocks, times (8) each... In addition to the parts I would have had to glass in new wooden backer plates to accomodate the larger base plate on the seacocks.... The bronze thru-hulls that I removed for inspection appeared to be like new and so I swapped out most of the ball valves and called it good. Reinstallation with liberal wrapping of Teflon tape and lots of torque had no leaks what so ever. Good luck.
The previous owner of my vessel has the replaced the gate valves with ball valves onto the original thru-hulls. While on the dry this past year I contemplated the replacement of the entire units. This would have involved not only the replacement of $30 balls and $40 thru-hulls with $85-95 seacocks, times (8) each... In addition to the parts I would have had to glass in new wooden backer plates to accomodate the larger base plate on the seacocks.... The bronze thru-hulls that I removed for inspection appeared to be like new and so I swapped out most of the ball valves and called it good. Reinstallation with liberal wrapping of Teflon tape and lots of torque had no leaks what so ever. Good luck.
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Tom Ehmke
Same experience here, Dale
difference being that I only replaced one which was cracked. 8 sounds like a lot of work and $$$. Tom
difference being that I only replaced one which was cracked. 8 sounds like a lot of work and $$$. Tom
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