manual bilge pump not sure if it works

[ErikKiekens]

My dear fellow sailormen,
on my brand new 2nd hand dufour I have tested the manual bilge-pump which was not easy. I had to connect a piece of hose and put that in a bucket of water.
Now if I pump I feel only air in the pumpbody. When I give up trying, half a bucket of water runs out of the pipe back into the bucket. Wondering if that's normal (I have never ever had to use a bilge pump in 30 years) I tied up the piece of hose and filled it with a few liters of water. I quickly felt water in the pump after a few strokes. After that, the pump was happy to empty the bucket without hesitation.
Is this normal behaviour? Is the pump body sucking air and should it be replaced? Or is it normal that it works only after some time and after some depth of water is established?
The electrical pump works fine.
Looking forward, as always, to your comments

Erik

 

[Seadawg33]

No it is not normal. I think you need to check the hose to see if there is a hole.

 

[vyv_cox]

I suspect that the discharge valve is not seating properly. It's easy to strip these pumps to check, and it's something well worth practising, as if you ever need to use it in anger the valves are certain to block with debris.

 

[Deleted member 36384]

It may be normal depending on the bucket test volumes. My bilge pumps will lift water when there is air in the pipe. The initial point when water and air meet the pump diaphragm is noticeable by the air and strangled bubble sounds but only for a very brief time. Then when 100% fluid is being lifted it sound just like water but with an air stream - sort of gurgling whoosh

When the bilge empties there is a period of air and strangled bubble noise as the pump lifts both air and water in slugs. In fact the faster you pump the more water comes up at this stage.

When I stop pumping a lot of water falls back down the hose into the bilge. I guess this is the water that was being part lifted as the air rushed by.

On your bucket test it may have taken half the bucket to get the hose filled followed by the pump drawing in air, so you never really experienced a good volume of water to test the pump. I reckon my pump takes about 4 good strokes (once up and once down on my pump is a stroke as it is single acting).

If you have any doubts open up the pump and inspect the valves and diaphragm. Stick a longer hose over the side and into the sea if you want to test it properly.

 

[rob2]

I've had similar problems with priming even a brand new pump. The two things I have done to solve the problem were to fit a strum box with integral non-return valve (stops the water running back down) and learn to "throttle" the handle so you can pump ridiculously fast until the water gets there.

Rob.

 

[lw395]

I used to race on a keel boat where you had to put your hand on the bilge pump outlet as a non return valve to get it to prime.
It's very common for them not to prime, especially if the hose to the bilge is long. A small bit of dirt stops the pump working with air.