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Bilge pump issue

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Created by Cockpit A week ago, 27 Nov 2019
Cockpit
96 posts
27 Nov 2019 7:02PM
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Hi all,
I noticed today that my auto bilge pump although activating when I lift the float switch is not actually pumping water out into the cockpit.
If I remove the pipe connected to the pump itself and activate the switch it will pump water into the bilge but when I reconnect the pipe although it still sounds like it's working nothing comes out of the other end. I have taken both ends of the pipe off and blown down it and there does not seem to any blockage at all.
So I can only think that the pump is not now strong enough to pump the water up through the pipe? Which means a new pump unless anyone has any other ideas?
One other thing, the pump has what looks like a small breather on top with a very small plastic ball under it, this was blocked and I did clean it but still not sure what it does exactly?
cheers

Cabron
NSW, 269 posts
27 Nov 2019 10:10PM
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Bilge pumps have good volume but very little head pressure, meaning they can't pump uphill well. What's the height from pump to cockpit? The height also decreases volume, so best to keep the exit(and all the pipe) as low and short as possible. Best to exit a through hull fitting just above the water line. Though, the issue when sailing or choppy moorings, water can flow back down...my current situation. I'm going to put a small loop in pipe just above through hull fitting to decrease the back flow chances. Secondly, smooth bore pipe is much more efficient than corrugated pipe, as the friction again decreases volume, and in effect the head pressure possible.
Hole on top... no idea, maybe a photo?

Jolene
1084 posts
28 Nov 2019 5:01AM
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The small tube with the plastic ball is an air bleed to discharge air from between the pump and check valve. The plastic ball is a float valve that seals the tube once the air has been discharged. It's basically to ensure that the impeller and pump housing are flooded.
If you have an airlock between the pump impeller and a check valve the pump may not prime.

Cockpit
96 posts
28 Nov 2019 7:25AM
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As can be seen it is pumping water but doesn't seem to have much pressure even though it looks ok in the photo.
The hole at top is where the plastic ball goes along with a small cap with holes in it. I did try it both with and without the ball and cap with the same result, it appears to be working but no water out the other end of the pipe and the pipe run has been the same for years so I'm not sure that altering it will help?

Cabron
NSW, 269 posts
28 Nov 2019 10:27AM
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Select to expand quote
Cockpit said..



As can be seen it is pumping water but doesn't seem to have much pressure even though it looks ok in the photo.
The hole at top is where the plastic ball goes along with a small cap with holes in it. I did try it both with and without the ball and cap with the same result, it appears to be working but no water out the other end of the pipe and the pipe run has been the same for years so I'm not sure that altering it will help?


Check voltage at pump, if a corroded connection it can still run but not at full speed or power.

Yara
NSW, 922 posts
28 Nov 2019 10:37AM
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Select to expand quote
Cabron said..

Cockpit said..



As can be seen it is pumping water but doesn't seem to have much pressure even though it looks ok in the photo.
The hole at top is where the plastic ball goes along with a small cap with holes in it. I did try it both with and without the ball and cap with the same result, it appears to be working but no water out the other end of the pipe and the pipe run has been the same for years so I'm not sure that altering it will help?



Check voltage at pump, if a corroded connection it can still run but not at full speed or power.


+1 That taped wire looks like a potential problem. If there is a joint in that, it is probably corroded, producing a voltage drop.

Harb
WA, 151 posts
28 Nov 2019 9:44AM
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Haven't pulled one like yours apart so this may not apply but if the voltage is alright I'd check the impeller housing for blockage or a broken blade on impeller.

Cockpit
96 posts
28 Nov 2019 9:45AM
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Cheers, will try checking the voltage when next down at weekend.

Trek
NSW, 875 posts
Tuesday , 3 Dec 2019 10:04AM
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I had that situation more than once with those red and blue bilge pumps. Both times It was a broken coupling between the motor shaft and the impeller. With no load it would appear to pump OK because the tiny friction between the motor shaft and broken plastic where it was meant to couple onto the impeller could get the impeller going. As soon as the output of the pump was blocked a little (with finger) the impeller wouldnt spin and water output would stop. I think the theory about the wire being high resistance (corroded) could be right too.

Cockpit
96 posts
Tuesday , 3 Dec 2019 6:46PM
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Select to expand quote
Trek said..
I had that situation more than once with those red and blue bilge pumps. Both times It was a broken coupling between the motor shaft and the impeller. With no load it would appear to pump OK because the tiny friction between the motor shaft and broken plastic where it was meant to couple onto the impeller could get the impeller going. As soon as the output of the pump was blocked a little (with finger) the impeller wouldnt spin and water output would stop. I think the theory about the wire being high resistance (corroded) could be right too.


I didn't get down at the weekend but that sounds exactly like my issue so will try both ideas when down again. Cheers



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