Galley Sink draining into Bilge?

[FAITIRA]

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Ok. Some questions here:

What is a one way valve (i'm sorry...)?
Would a manual pump like the Whale Urchin keep water out or do I need a "one way valve" still. Would water flow through it when stopped?

I will most likely go for an electric pump as it's much easier to fit a small switch with pump underneath rather than a manual pump that needs to be operated with a handle.

Looking into centrifugal pumps now...

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One way valve, water will only flow one way.

Water will not flow through an 'urchin' without pumping, but a very few strokes will clear the sink.

The discharge valve in the urchin will act as a nonreturn.

An electric pump, 'especially' a centrifugal pump will be a constant source of problems as it will block/jam very easily, a suitable pump that can handle solids would be pretty expensive and totaly unecessary. imho.

 

[fluffc]

Thanks all for your comments. I have taken the plunge and gone for a Gusher Urchin diamphram pump and a divertor valve so that it can be used for the bilge pumping too.

 

[mixmaster]

Thanks for all your help as well. And sorry if I slightly hijacked your thread fulffc! This is what I understand so far:
If I add a diaphragm pump, whether a manual like the whale urchin or electric, it will not let water in but will let it out (but it is bad practice to rely on this to keep water out of the boat).
I see 2 solutions:
1) Use a y valve diverter so that when in harbour the sink can drain straight down to the through hull and when at sea it is diverted to the pump. Is this necessary?
2) Put the pump straight in line of the hose that goes to the through hull so that it can give the water a pull/push out of the sink. When the boat is upright, will the water "drop through" the pump without running it or would I then always have to use the pump with this set up?

Thanks again.

 

[vyv_cox]

I would go for your 2). Avoid diverter valves if you can in most circumstances. In theory the water would drop through but it depends on head, system resistance and the like. Have a look at the foot operated pumps intended for fresh water supply, might work quite well if they come big enough. If the pump blocks it should be fairly easy to free with a bucket of water in the sink.