Check valve???

Project_Mayhem · Thursday at 6:45 PM

I know someone is going to say that check valves can get clogged so what about loop to trap some water? You'll probably end up with an air/water mixer for a few seconds but it's better than straight air. Or maybe a large raw water filter could act as a buffer?

Dare I say it... Shouldnt you close your through hull when you leave the boat?

dlochner · Thursday at 7:16 PM

No check valves on the intake. The water in the intake line will be at the waterline of the boat. So long as the hoses to the raw water pump intake are at or below the water line and the raw water pump is at or below the water line, everything will be fine.

Ralph Johnstone · Thursday at 9:45 PM

Project_Mayhem said:
Dare I say it... Shouldnt you close your through hull when you leave the boat?

How can you bring yourself to say something so simple and straightforward ?

How is anyone supposed to argue with something that uncomplicated ? Now what do we do with all this spare time ?

You know, I would hope, that idle hands are the tools of the devil :facepalm:

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jssailem · Friday at 2:20 AM

The concern is a non concern if you check and replace your impeller on a regular basis. It is considered a consumable piece of gear. It can run dry for a short period.

Project_Mayhem said:
Shouldnt you close your through hull when you leave the boat?

Straight forward resolution to the concern.

I solved the run dry fear be installing a strainer that has water in it, and shutting the valve on the thru hull when leaving the boat.

Behold the Groco ARG750 series .

Easy clean, easy to tell you have water in the system.

Davidasailor26 · Friday at 3:00 AM

I agree you’d be adding another potential point of failure for no value. The impeller itself is a positive displacement pump and should have limited backflow as long as the vanes are intact. Every inboard powered sailboat for the last 50 years has been built without check valves and impellers work just fine unless the intake gets blocked.

sailme88 · Friday at 3:16 AM

Interesting thought on a problem solve.. But before the solve, the why should be known. Hoping that you are always closing the raw water intake valve when leaving the boat. I hate to use this word.... but ASSUMING that the impeller is good. If so, it should act like a thumb over the end of a straw and create a vacuum within the feed line. So, IF you are closing the valve and IF the impeller is good, then the issue must be with the feed line. Check the feed line connection to the pump body for a tight seal. Like with the straw, a hole at the furtherest end will still hold fluid to that point. But up near the thumb...not so much

AS stated above....KEEP THE INTAKE VALVE CLOSED....many an insurance claim gets denied because of this!

Captain Larry-DH · Friday at 3:29 AM

sailme88 said:
many an insurance claim gets denied because of this!

I have not heard of this. It’s not stipulated in any policy I’ve ever had, and boats under sail don’t close them.
In practice, I don’t close them if we’re planning to return to the boat within the same day/night or sleeping aboard. However, it’s prudent to close them before leaving the boat for a longer period of time.
If the intake hoses don’t have an air leak and the impeller/pump is serviceable the system won’t lose prime, and if pulled from the water (or opened, such as when cleaning the raw water strainer) will quickly regain prime after launch.
So the answer to OP is that he has some maintenance/fixing to do.

dlochner · Friday at 3:52 AM

Closing the seacock, while an oft recommended practice, isn't necessary if the hoses are in good shape. Siphoning isn't an issue either providing the engine is plumbed correctly with a vented loop between the heat exchanger outlet and the exhaust elbow.

Terry Cox · Friday at 4:02 AM

Good morning, Fred. Several helpful poster comments thus far, and I agree with most. No need for a check valve unless you have issues up stream; such as missing impeller vanes, leaking hoses that need replacing, etc. I keep my engine sea water through hull valves open always [all others (heat pumps, toilet, etc.) I keep closed when not in use]. Both sea water strainer input ports (main engine and Genset) are above the water line. Since the system remains sealed, there will always be sea water in the line after engine shut down. Likewise, sea water will remain in the line between the engine and pump. The pump impeller that has been in use since before our purchase in 2002 looked like new when I replaced it a year ago. Even after splashing when the boat has been out of the water for several days, I've never had to prime the system. Given these factors, I would say go ahead with a check valve if it gives you comfort, but unnecessary, IMHO.

east coaster · Friday at 4:06 AM

Regarding insurance, you never know what questions or documentation you will be asked until you submit a claim.

Captain Larry-DH · Friday at 5:59 AM

east coaster said:
Regarding insurance, you never know what questions or documentation you will be asked until you submit a claim.

Not a lawyer, but they should pay that claim if they don’t stipulate something in the policy or application. They might argue “gross negligence” but that’s debatable. Whether it ends up in dispute probably depends on the carrier.

Project_Mayhem · Friday at 6:19 AM

How's a liveaboard supposed to use the head if it must be closed? I'm sure some boat out there has a seacock on a bilge pump.

I have had a couple of seacocks with a slow leak when closed. Water would seep in/out over the course of hours or days

jssailem said:
The concern is a non concern if you check and replace your impeller on a regular basis. It is considered a consumable piece of gear. It can run dry for a short period.

Straight forward resolution to the concern.

I solved the run dry fear be installing a strainer that has water in it, and shutting the valve on the thru hull when leaving the boat.

Behold the Groco ARG750 series .
View attachment 231987
Easy clean, easy to tell you have water in the system.

This is exactly what I had in mind but then again, I own one

dlochner · Friday at 6:57 AM

We're drifting way off topic with insurance considerations. Since it has been raised....

Liability insurance only won't cover the loss of a boat sunk because of a failed sea cock, hose, or whatever. It may cover cost to salvage the boat.

Yacht policies, with Agreed Hull Value, usually have a "consequential damage" clause. This covers damage to the boat that is the consequence of something not covered. So, if the boat was damaged because a hose had not been maintained or a seacock failed, the repair cost would be covered except for the failed hose or seacock.

Davidasailor26 · Friday at 9:14 AM

fred1diver said:
Yes I do always close the valve, even when under sail.

I don’t think I’d be comfortable closing the seacock when sailing, at least not around here. Every once in a while there’s commercial traffic or some other reason to beed the engine relatively quickly. Pretty sure I’d forget to open the seacock then, or at least I wouldn’t want to spend the time on it. The risk of a hose failing and causing a serious issue when you’re on the boat and awake is pretty minimal relative to the risk of needing the engine.

Stu Jackson · Friday at 9:32 AM

fred1diver said:
Yes I do always close the valve, even when under sail.

That makes no sense, and is dangerous if you need to start your engine in a hurry. I once found a wind hole right in front of a ferry!!!

thinwater · Friday at 10:30 AM

Captain Larry-DH said:
I have not heard of this. It’s not stipulated in any policy I’ve ever had, and boats under sail don’t close them..../QUOTE]

Most policies have a contingent damamge exclusion; they cover the incident itself, but not damamge due to wear items and not damamge that happened due to, for example flooding, after the event.

In the case of leaving a seacock open, the flooding was probably caused by failure of the hose, which unless it was knocked off during a roll-over or collision, is the result of neglect and is an excludes wear item that is not covered. The flooding of the boat happened as a result of the hose failing. The result can be no coverage, since there was no accident.

Some equivalents. Your house has water damamge because the roof was old. Neglect, poor maintenance, no coverage. If a tree landed on the roof, that is an incident. Your car gets a flat. You continue driving it to an exit ramp or to the shop, the tire shreds, the rim is dented, and body work is damaged. The flat tire is a non-covered road hazard, and the rest happened because you didn't call for a tow. No coverage.

It depends on the policy, but if your boat sinks due to a failed hose or bad clip, there may be no coverage. So close the through hulls. I always have. If you are afraid you will forget to open it, hang the key on the valve. You can also add (many engines have this) a no-flow interlock with a short time delay.

Rich Stidger · Friday at 11:30 AM

While it's true that water in the cooling circuit will seek the sea level, if the water level in the hoses drops, that suggests to me that there is an air leak somewhere.
I would find an fix that leak.
BTW, how do you know the water level drops? The hoses are usually opaque.

Check valve???

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SBO Weather and Forecasting Forum Jim & John

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