Raw Water Anti Siphon Vented Loop

[wingssail]

Originally Posted by HeinSdL

Checking the proper operation of the anti syphon valve yearly is thus to be recommended (extremely simple, it's just a spring loaded device allowing air into the system when the pressure inside drops). The small valve can get stuck in place leading to problems.

I recommend a different type of syphon break, that of a small pipe coming out of a "T" at the top of the loop with a small adjustable petcock on it. This pipe can go into a cockpit drain or a sink or somewhere. You adjust the petcock until only a small spray or dribble of water comes out when the engine is running. That water runs harmlessly into whatever drain you have. When the engine stops air goes into the petcock and breaks the syphon.

Wit this system you get used to the sound of the water flowing out of that little pipe and you know no blockage has occurred. If you don't hear the water running you need to clear the line, usually by opening then slightly closing the petcock.

if this is in the cockpit drain then you might want to close that petcock if sailing in severe storm condition with the engine off so that water does not fill the cockpit and then begin filling your vented loop.

[FPNC]

A sailboat needs a vented loop in the hose that injects water into the exhaust. Done period.

That vented loop should be as close to center line as practical and at least 18 inches above the highest water line. The highest water line may be when the boat is heeling. Or, it may be highest while sailing offshore with a heavy following sea. You have to place the vented loop for the worst possible scenario. Not tied to the dock.

[rowansmith]

Originally Posted by FPNC

A sailboat needs a vented loop in the hose that injects water into the exhaust. Done period.

That vented loop should be as close to center line as practical and at least 18 inches above the highest water line. The highest water line may be when the boat is heeling. Or, it may be highest while sailing offshore with a heavy following sea. You have to place the vented loop for the worst possible scenario. Not tied to the dock.

What happens if the vented loop cannot be 18" above the water line?

What's the impact if it has to be lower due to the height available in the engine room and the layout of the vessel?

[FPNC]

Originally Posted by rowansmith

What happens if the vented loop cannot be 18" above the water line? What's the impact if it has to be lower due to the height available in the engine room and the layout of the vessel?

Then your risk of shipping water through the raw water circuit increases.

[rowansmith]

Originally Posted by FPNC

Then your risk of shipping water through the raw water circuit increases.

But presumably it would be less than the risk of having no siphon break? Eg it wouldn't make the situation worse?