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Old 17-01-2010, 16:52   #1
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Sea Chest Check Valve

I currently have a sea chest there is a vent line it is approx 18 inches above the water line. I belive I am getting water out of it while sailing dues heeling and maybe some bubbles of air entering the intake. Need to figure out a soultion to this. Short term solutions plug the vent line or add a check valve long term would be to raise the height of the vent.
1. Is a vent required by ABYC standards?
2. If yes to # 1 should it have a check valve on it.
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Old 18-01-2010, 14:31   #2
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If the vent is to vent the sea chest I think you do need it.
Where is the other end...seems it could just go through the hull near the gunnels...I don’t know what difference it would make if it gets air or water in it....Am I missing something?
I thinks plugging and putting a check-valve are not the right thing to do.
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Old 18-01-2010, 22:14   #3
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Not sure I see a reason for the vent, how many boats have the sea water line for the engine vented? The air if any will get out through the engine raw water wash down pump, or genset raw water or in port AC. Having the vent allows air out at the high point but also allows water into the boat. The other end is inside the boat 12 to 18 inches above the water line. I do/can see a problem when you are hauled and go back in to the water.
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Old 19-01-2010, 05:29   #4
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Quote:
Originally Posted by Gudgeon View Post
I currently have a sea chest there is a vent line it is approx 18 inches above the water line. I belive I am getting water out of it while sailing dues heeling and maybe some bubbles of air entering the intake. Need to figure out a soultion to this. Short term solutions plug the vent line or add a check valve long term would be to raise the height of the vent.
1. Is a vent required by ABYC standards?
2. If yes to # 1 should it have a check valve on it.
A check to stop water from going out the box via the vent would basically stop it from being a vent (except for leakage). While not just make the vent higher up ensuring it is on ceneterline of the boat?
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Old 19-01-2010, 11:49   #5
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I'm pretty sure the vent needs to be there other wise you will have pressure differential in the box...it should be at atmospheric pressure.
I agree with Don and you ...add to the hose and extend it up further.
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Old 19-01-2010, 19:29   #6
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A check to stop water from going out the box via the vent would basically stop it from being a vent (except for leakage). While not just make the vent higher up ensuring it is on ceneterline of the boat?
No in some hydraulic apllications we have check valves that are open wnd the flow will shut the check. There are applications for ponds and irragation that are flapper type valves that also do this. Currently raising the height is not an option, it will never be on the center line. a float valve would also work if I cold find one in the correct configuration.


"I'm pretty sure the vent needs to be there other wise you will have pressure differential in the box...it should be at atmospheric pressure.
I agree with Don and you ...add to the hose and extend it up further"

What type of pressure difderential do you think there will be at 3-4 feet of sea water maybe 1 half of pound. I still see this as a hole in the boat to the ocean.
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Old 19-01-2010, 19:39   #7
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You need the vent.. A sea chest is prone to air locks if the vent is blocked. Without a vent, entrained air in the chest can eventually accumulate with sufficient pressure to prevent further water inflow. Either extend the tube or lead it overboard above the waterline.

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Old 23-01-2010, 01:51   #8
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Gudgeon
I can see where the chest could fill with air and actually push the water line down to the point to where the pick-up lines would no longer be in the water.
Why is raising the height of the vent not a option?
Any pictures?
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Old 23-01-2010, 03:41   #9
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Just found this thread...hope it helps.
No Underwater Through-Hulls?
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