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Old 08-26-2008
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Thu Hulls vs Seacocks

This weeks learning part two (since I can not seem to find the answer in print on the internet)...

Seacock’s and thru hulls, easy to see the difference but where and why would you use one over the other. Curiously, both heads and the galley sink used seacock’s and the raw water for the reefer and engine were thru hulls with ball valves as were the cockpit drains (planning changing to side discharge).

We plan to ocean sail but money is what it is and we need what we need...

What do we need?

I'd rather throw all seacock’s at it but the cost is 3-4 times higher and I have 4 thru hulls per head, 1 for the galley sink - (side discharge) and then 4 more in the engine compartment. Cockpit, engine raw water, reefer in and out

I'm not really looking to reduce thru hulls though I know some captains advise just that - I'm looking for the how and why of using one over the other.

Thanks again in advance!
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Old 08-26-2008
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Bruce-

Your OP isn't all that clear, since each seacock has to be attached to a through hull, with a flanged adapter between it and the through-hull.

What are you defining a seacock as and how does that differ from a ball valve and through-hull.

You could really reduce the number of through hulls by using a saltwater manifold system for the seawater coming aboard.
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Old 08-26-2008
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I'm defining a seacock as the upper unit with a brass flange and ball valve incorporated and a thru hull (fitting) as the lower end of a seacock with a nut on the inside of the hull instead of a "seacock"
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So, what you're saying is that his is a through-hull:



And that this is a seacock:



BTW, if your boat has brass for either... you're in trouble... it really should be BRONZE. Brass has no place on a boat, especially below the waterline.
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Old 08-26-2008
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I'm sure it's bronze, I can not view your pictures for some reason but when I said "tru -hull" I meant the mushroom with a backing of some sort on he inside of the hull and a bronze nut - typically a ball valve is attached. A seacock uses the thru hull mushroom but has teh bronze flange and incorporated ball valve. When you mostly work and sail alone many of the right terms can elude you when talking with others.
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Old 08-26-2008
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I think that I know what you mean. You define a thru-hull as the fitting that goes through the hull and to which you can attach a valve of some sort - like a ball valve. You seem to define a seacock and an integrated through hull fitting and valve. If I'm wrong, stop reading.

I personally like tapered Spartan seacocks because they are serviceable. The ball valve, while very reliable is not serviceable (at least in my experience). If anything happens in the way of a leak, you don't have much recourse. Since there are two parts to join (the through hull and the valve), it's just another area for a potential leak. I've serviced my Spartans many times with grease and occasionally with valve grinding compound (in the rare event of a bound seacock). You probably already know this, but do not use a gate valve anywhere on the boat.

IMHO, REALLY humble opinion, this is definitely not an area to save money. I am absolutely rabid about leaks, especially those below the waterline. Since I like to sleep at night, I'd spend the bucks to get the best, like Spartan, but there are others.

In the interest of full disclosure, I'll admit that the raw water cooling inlet to my A/C unit has a ball valve that I plan to replace. Whoever installed the unit used a ball valve and modified garden hose. I installed reinforced hose; the valve is next.

Y'all - Please don't jump on me about this. I know that many manufactures use ball valves and the boats float, but I really like to be able to inspect, grease, and adjust my seacocks. Just my $0.02...
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Old 08-26-2008
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I agree... this is whats on my boat...cant buy better insurance IMHO.
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Old 08-27-2008
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I had the ball valve setup when I bought mine... later after the engine was out, I lightly tripped over the ball valve in the engine room attached to the thru hull and it broke clean off. I was on the hard at the time, since then - 1980 model - I have removed them all for replacement and will be replaceing with seacocks. Thank you for the reply's.
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Old 08-27-2008
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I had a seacock break off in the slip and was able to stop up the hole. After 29 years (Paloma is a 1979 Bristol) it was eaten up by electrolysis - probably the same thing for yours. I replaced all the thru-hulls and seacocks.
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There should be no confusion in terms.

A thru-hull means exactly that: it's the portion that goes thru the hull.

A real marine seacock has a flange for thru-bolting and NPS threads on the bottom side, to mate with the NPS threads of the typical thru-hull fitting. It has NPT threads on the top side, to mate with NPT pipes and hose barbs.

A ball-valve, generally, is a less-expensive device with a lever which connects in some fashion to the thru-hull. Care must be taken to ensure that the threads match (NPS-to-NPS). Since most ball valves come with NPT (tapered) threads, an adapter is required for them to mate correctly to the threaded thru-hull. Groco makes such an adapter.

Failure to pay attention to thread-mating can sink your boat.

Failure to ensure that all metals are intended for marine use (i.e., bronze or stainless) can also sink your boat.

There's an excellent tutorial on seacocks, thru-hulls, etc. on HaleKai's website: Boat Projects Gallery Photo Gallery by Maine Sailing at pbase.com

Bill

Last edited by btrayfors; 08-27-2008 at 08:12 PM.
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