Non return valve to suite 1 1/8th pump outlet

theoldsalt

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I thought pump outlets were fitted with one way valve (NRV ?) as standard.

Or do you mean on the pump inlet? If so then fit one to the strum box.
 
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GrahamHR

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My (centrifugal) bilge pumps allow water back into the bilges when they stop running; not a huge amount, just what is above them in the outlet pipework. No valves. They are in the lowest point in the bilge cavities.
 

vyv_cox

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I suggest that it will never happen. Pumping a bilge totally dry is impossible, the pump cannot pick up once some air is being drawn into its inlet. The only way is to use a sponge or cloth for the last dregs.
 

pcatterall

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I suggest that it will never happen. Pumping a bilge totally dry is impossible, the pump cannot pick up once some air is being drawn into its inlet. The only way is to use a sponge or cloth for the last dregs.
Yes that is fairly obvious but the pump gets my bilge nearly dry but then a lot flows back when the pump is stopped ( a lot of sponge fulls!!)
 

pcatterall

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David2452

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Many new centrifugal pumps including Whale and Rule actually come with a joker type valve on the outlet spiggot. I tend to leave them on "low head" installs and remove them where the pump has a harder job. The only time they really do any good is where enough water is allowed to flow back and re trigger the pump but that is better addressed by using a pump or switch with a time delay like the new Rules that run for 30 seconds or so after normal switches would turn off
 

lw395

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Non return valves seem to become 'slow return valves' as soon as a tiny amount of dirt is added to the water.
I've got one of those plastic stirrup pump things, mostly used for emptying the dighy, but also good for emptying the shower sump etc. With adapter down to quite small hose it would do what you want?
Alternative is another manual bilge pump rigged with small hose, it will be better at pumping a mix of air and water?

The only proper answer is to cut off the souce of bilge water....
 

VicS

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Yep! makes sense...... all that standing water in the discharge pipe is too much for the pump but then( second thoughts?) once the pump has re-filed the pipe isn't it having the same work to do?

will pump against that head but perhaps not designed to start against that static head
 

Len Ingalls

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A manual "whale" type pump with a rectangular strainer that lays as flat as possible to bilge bottom works decently. Still have to sponge the dregs,but mine will suck down to 1/4" (6mm) or so. / Len
 

ghostlymoron

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If its a centrifugal pump, it will 'slip' until its built up enough pressure to commence discharging. 'Cycling' is a big problem with an automatic pump which will restart if there's enough water in the discharge pipe to raise the water level in the bilge sufficiently to re-trigger the float switch. Its unlikely that an nrv will seal positively enough to stop it unless it's a spring loaded one (which then will reduce the pump output).
Perhaps the answer is to fit an additional small capacity, non automatic pump to remove the residue after the main pump has stopped.
 

pcatterall

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This is not a ‘main’ pump just a little one sited right in the lowest part of the bilge. It is not automatic. I think I will just keep a small hand pump to pump into a bucket for the times I want to get my bilges really dry.
Thanks all.
 

lw395

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This is not a ‘main’ pump just a little one sited right in the lowest part of the bilge. It is not automatic. I think I will just keep a small hand pump to pump into a bucket for the times I want to get my bilges really dry.
Thanks all.
My old boat has a little sump from which the main bilge pump drew.
I used to empty the sump with a 4mm bore tube on the end of a big syringe, after cleaning the bilge or if any rain or spray got in, or when we'd chucked wet kites below etc.
Getting the bilge as dry as you can makes a big difference to the freshness of the boat if you leave it shut up in warm weather.
 
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