Bilge pump thru hull

[radicalcy]

I've installed two new 12 volt bilge pumps on my classic Columbia Sabre. The single manual pump exited at the head discharge below the water line.I intend to seal this thru hull and route the head to a holding tank. Four other thru hulls all exit below the water line. I want to route the new pumps to a new above the water line thru hull that won't siphon when the boat heels 30 degrees which is just about normal sailing angle for the boat. Should I go to the transom, and install a ball cock with a one way valve?
Larry Wilson
1966 Columbia Sabre
"Wild Swan"
Richmond,Va

[Tim]

If you run the discharges to the transom, you'll be fine for all normal sailing applications. There's simply no option but to run the discharge outside the hull somewhere, on any boat--coastal or offshore. All you can do is look for locations that won't obviously and repeatedly be submerged during normal sailing conditions. Occasional submersion, such as in a counter or some such, is OK, particularly if you can run the discharge hose in a high loop just before the exit. The siphoning pnenomonon happens most often when the pump discharge is located close to the waterline on the side of the boat; heeling can deeply submerge the outlet and may set up an easy back siphon through the pump. But this just doesn't happen with any discharge that is thoughtfully mounted.

One-way check valves are a great idea in concept, but are notoriously prone to failure and clogging. I'd eliminate that from the plan. Putting a true shutoff valve on a bilge pump is a bad idea because, frankly, you never want it closed, and forgetting to open it before the pump ran could lead to unpleasant circumstances. No boat is watertight enough to prevent the ongoing need for a bilge pump, so even in an offshore storm (worst case scenario), I can't imagine wanting to close it off.