Siphon Loop

[Billy654]

Have a 1980 Catalina 30. The vented loop is under the galley sink. The hose at the top of the vent goes back down into the bilge. I noticed that when the engine is running that water is coming out of the hose in the bilge. Is this a problem? What do I need to do?

[BELLATRIX1965]

Wow! You need to install a new check valve at the top of that loop - ASAP! If there isn't one there now (hard to tell), there should be! The loop is a vacuum breaker, and should not allow liquid to flow back to the bilge! Also, those hoses all look pretty nasty (old and cracked!) - I'd do myself a favor and change them all with approved "exhaust" grade marine hose before you find your boat on the bottom! Happy plumbing!

[Billy654]

Bellatrix1965

Hoses are going to be replaced. Wouldn't routing the vent hose back down to the bilge defeat its purpose?

Anyone know if this is where Catalina Places their vented loop?

[svHyLyte]

I find it hard to believe that Catalina would have installed a vented loop in such a half-as_ manner. The top of the loop and the end of the vent line need to be above the water line on all points of sail. The vent line should permit air to enter the loop but disallow water to emerge. If it does, the valve is fouled and should be removed and cleaned. Some can be restored to functionality but many cannot and need be replaced. FWIW you might want to take a look at Servicing Raw Water Vented Loop - Vetus - Cruisers & Sailing Forums