Bilge pump non return valve

[Andrew_Trayfoot]

I am in the process of fitting a new manual bilge pump.
The strainer has a non return valve unit in.
Would it be a good idea to fit a second one between the pump and the skin fitting?

 

[JumbleDuck]

I am in the process of fitting a new manual bilge pump.
The strainer has a non return valve unit in.
Would it be a good idea to fit a second one between the pump and the skin fitting?

There is no point in doing so.

 

[sarabande]

I'd consider adding an upward loop (inverted U bend) just before the pipework exits the hull.

 

[neil1967]

U bend with syphon break absolutely essential if there is any chance of the skin fitting being immersed - we had water syphoning into the bilge when strong winds kept the yacht heeled over in a marina and the skin fitting was held under water (though an oversight the bilge pump was off).

 

[duncan99210]

There’s no point in doing, as JD says. First off, you’ve already got a none return valve at the strainer. Secondly, the pump, if it’s the normal diaphragm type, will also act as a none return valve.

 

[lw395]

The skin fitting should be somewhere on the hull which is only rarely underwater and never for long.
Under the gunwhale close to the transom is a popular choice.
Or you can put it lower in the transom in which case a raised loop of hose is a good idea.
An extra non return valve beyond the two in the pump and the one in the strum box is just extra exercise for the person doing the pumping.
I race a bit on open boats which leak. The difference that convoluted plumbing makes to getting the water out is quite tangible.

 

[Andrew_Trayfoot]

Thanks for the input.
Skin fitting will be just under the gunwhale right aft.