Open or closed seacock

[GordMay]

Originally Posted by boris

i have never heard of a "sea chest" sounds brillant what are the down sides, the only thing i can think of would be that you may have more pumping to get the water going

I can only think of a few minor potential down-sides to a “proper” Sea Chest:
- Single water supply (thru’ hull) may become fouled, starving all water supplies.
- Initial through-hull sized to accommodate initial demands, may not satisfy additional loads.
- A large water consumer (engine) may starve other consumers.

[JB]

Sorry...I didn't catch the drains part of the question. Each system served by the sea chest has its own "drain" - the heads normal discharge, the engine and generators discharges through the water lift mufflers, the watermaker has its own discharge. All are siphon vented loops, with loops well above the water line.
Does that answer your question?

[Wotname]

Yup, thanks JB.

[bob kingsland]

I have 2 below the water line thru hulls on my boat: main raw water in, and head exhaust. Because I made both totally accessible, I never leave the boat for any length of time without closing them... it's too easy to even think about not doing it. All others are above the waterline; for example head sink, galley sink, shower, aft cabin sink and reefer drain all go to a sump tank with a float switch which exits above the water line. Gord's point about fouling the main 2" inlet is my only concern, and there's a big strainer downstream of it to help with that. Details on the website under gallery-systems.
Of course, you do have to remember to turn raw water back on before starting engine, as it could get expensive if you don't. But that soon becomes second nature, especially if you hang the key on the valve.
Best, Bob S/V Restless

[GordMay]

Originally Posted by bob kingsland

... Gord's point about fouling the main 2" inlet is my only concern, and there's a big strainer downstream of it to help with that.

Of course, this feature is a two edged sword, because there's only one intake to inspect & maintain.

BTW: it seems we are really discussing an intake "manifold" system, rather than a classic "sea chest".

Originally Posted by JB

Sorry...I didn't catch the drains part of the question. Each system served by the sea chest has its own "drain" - the heads normal discharge, the engine and generators discharges through the water lift mufflers, the watermaker has its own discharge. All are siphon vented loops, with loops well above the water line.
Does that answer your question?

Almost.
My question was a bit of a tounge-in-cheek poke at "marketers" who suggest that the presence of a sea chest or intake manifold reduces all through-hulls to one. Of course, most (tho' not all) thru' hulls are above the waterline, so a sea chest can reduce the number of below-waterline openings to about three (1 intake, & 2 sink drains, & perhaps a sanitary drain = 4).

Do your sink drains have vented loops?

[MarkJ]

If you are talking about the raw water inlet seacock then you aint seen where it is on a Beneteau. To fondle it you need to rip up the mattress in the aft cabin and lift the board under same, lie down on the opening and reach down into a black abyss....

And if you are talking about all the seacocks.... well it would take us all day... there are hundreds of them perforating the bottom!

We leave all on all the time

Mark

[JiffyLube]

I personally only know of one boat that sank in its slip because of seacocks, and that was because the seacocks corroded out between the thru hull and the valve...closing these wouldn't have made any difference.

[Therapy]

Originally Posted by JiffyLube

I personally only know of one boat that sank in its slip because of seacocks, and that was because the seacocks corroded out between the thru hull and the valve...closing these wouldn't have made any difference.

I know of the same situation at Bahia Beach Marina (gone the way of condos) many years ago. Someone noticed her low in the water and saved her.

[bob kingsland]

We had one almost sink in my harbor last summer... a smaller 25 year old Perko inlet strainer, the kind with a top that flips up on a pin going through 2 ears, with wing nuts. The pin corroded away, the lid began bouncing gently up and down, very slightly with each small wake. Battery ran down, and after 2 days she looked a little low in the water. Harbor master asked me to go check, when I got to the boat the water was at the level of the salon cushions. We got her to the dock and got a basement sump pump going, and the owner was very lucky... only needed a new water heater, starter motor, , and some wiring. If he had closed the sea cock it wouldn't have happened... he would have noticed the fault in the strainer when he next opened the sea cock. Bob S/V Restless

[MidLandOne]

I don't know the statistics for sinkings or partial floodings of pleasure vessels from back flooding but a few years back I was involved in asking insurers for items they would like checked when our surveyors (at that time) did inspections.

Top of the list was anything that could siphon back including looking out for hoses hanging over the side (inshore fishing boats usually have a short big dia hose just long enough to hose around the working deck and often just throw the discharge end over the side when not in use). Apparantly, sinkings or floodings when the vessel was alongside the dock was a major cause of claims.

Personally, I would always protect such things myself, that with a ventilated loop or other automatic protection (re automatic protection eg our grey water, which could backflow back through the shower tray and flood the boat, is protected by the grey water pump valving which positively prevents reverse flow plus another non return valve added for "just in case").

[MidLandOne]

Oh, and got a bit carried away , meant to end up with "...And would personally recommend closing all seacocks if the boat is left unattended for other than a short time."

[Celestialsailor]

Loaded question actually...When I'm running back and forth to the boat store, I do not close. When I leave for an extended length of time, I close all below the waterline. The engine inlet is always closed immediately after the engine is shut off.

[GordMay]

Most of the flooding stories (whatever the cause) suggest the use of a high water alarm that publicly signals outside the boat.

[speciald@ocens.]

I have 24 thru-hulls with seacocks - yes , that's 24. We live aboard and never close any seacocks.

[S/V New Sensation]

Closed every time. Recently had a wake up call on why this is important when the vented loop on the shower sump plugged. My wife had just finished cleaning up and I was doing some boat projects before taking a shower. Heard an odd running water noise and there was the shower sump siphoning back into the sump. Just another reason I like a closed valve in lieu of relying on the automatic system.