Non return valve on bilge pump

I have a manual bilge pump. I was going to fit one at the end in the sump. I hope it will stop water draining back down the tube when i stop pumping
 
As usual, it depends. If the pump is a diaphragm type there is no benefit in a NRV because the pump has valves that work in the same way. If the pump is a centrifugal type it helps to have the NRV at the lower end of a column, where the weight of water will help to close the valve. Be aware that a NRV will reduce the flow and head of the pump.
 
skipper681 said:
Is it a good idea? If so where would it go? In the bilge beside the pump or high up on the transom where the water exits?
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Be aware that if you have a long pipe run between bilge and outlet (my boat as built has about 20 ft) any non-return valve will soon become not quite perfectly sealed and slowly leak the column of water back into the sump, re-triggering auto bilge pump. Repeats infinitely. I thus never leave the bilge pump switched on to auto.
 
I should have explained it was a Rule centrifugal pump, Steve you don't need one in a manual pump as they already have them built in, like Whale etc. vYv your answer makes so much sense thank you, I was wondering this forever but when you mentioned the weight of the water It struck me, I should have thought of that lol.

If I may ask one more question.... Would running the electric pump through the hand pump tube be a good idea? (through the Whale gusher that has the valves built in)
 
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jwilson said:
Be aware that if you have a long pipe run between bilge and outlet (my boat as built has about 20 ft) any non-return valve will soon become not quite perfectly sealed and slowly leak the column of water back into the sump, re-triggering auto bilge pump. Repeats infinitely. I thus never leave the bilge pump switched on to auto.
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You could maybe raise the float switch.
 
You can pump through the manual pump but will lose the facility to run both together. I decided to fit a separate outlet for my electric pump with a nrv fitted near the pump outlet. Never had any trouble although a bit of grit can cause it ti leak back a bit. As Vyv says a nrv will reduce the flow so fit a bigger pump.
 
If there's enough water in the delivery pipe to raise the level in the bilge when it drains back to a level that switches the pump back on, the pump will continue to cycle on and off till your battery runs down. So you're forced to fit a nrv. (in my opinion)
 
ghostlymoron said:
If there's enough water in the delivery pipe to raise the level in the bilge when it drains back to a level that switches the pump back on, the pump will continue to cycle on and off till your battery runs down. So you're forced to fit a nrv. (in my opinion)
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Yes, but the first tiny bit of grit or hair lodging in the seal of the NRV will break the perfection of the non-return seal, and the water in the pipe will very slowly trickle back. If you have a big wide bilge base it is unlikely to be enough depth to re-trigger the float switch, but if a small sump and a long pipe run the float switch will trigger the pump again, on and on till the pump dies or the battery is flat.

And in response to the suggestion to raise the float switch, all that does is vary the level of water left in the bilge. Fortunately my hull itself does not leak, but the occasional drip from the calorifier pressure relief valve, condensate from the bottom of the fridge, and seawater getting in when you clean the log impeller mean there is always some bilgewater.
 
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