Non return valve

[Palmtree]

Any thoughts on these, as I will need to fit one in a 3/4inch pipe from the bilge pump. The outlet is only just above the waterline and under the water when heeled over when sailing. The manual pump has a non return system built in but the electric pump does not. If I just join into the outlet pipe alone the manual pump will return the water to the bilge via the electric pump. Are there any better than others?

Ian

[Antares_9]

Follow your engineer's instincts Ian, the simplest valve is probably the most reliable, I quite like the flapper valve,but the safest and most reliable is a seperate line for each pump. Redundancy without intervention for each.