Water Pump Not Priming

jviss

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Feb 5, 2004
6,745
Tartan 3800 20 Westport, MA
Here's my new theory. Pump pumps air into the output line once the tank is dry. But, the pump can't compress air to the cut off pressure, 30psi. So, the pump runs, with nowhere to put any water it's picked up.

I bet that if I opened a tap and dumped 2 gallons of water that's in my accumulator, then got to air, the pump would start pumping water again, and would shut off once the accumulator was recharged. I'd rather fix the airlock than waste the water. The air eliminator should do the same thing as dumping the water, or bleeding from a T, as you suggest.
 
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Jim26m

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Apr 3, 2019
579
Macgregor 26M Mobile AL
Certainly worth a try!

The way I was thinking you would waste virtually no water, but automatic is better.
 

Jim26m

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Apr 3, 2019
579
Macgregor 26M Mobile AL
You will likely put the tee in for the auto bleed anyway.

Good luck! Hope the auto bleed gets it.
 

Jim26m

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Apr 3, 2019
579
Macgregor 26M Mobile AL
Right, but the one I'm showing keeps you from bleeding the accumulator while purging the air.

Not necessary for the auto bleed.
 

jviss

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Feb 5, 2004
6,745
Tartan 3800 20 Westport, MA
Right, but the one I'm showing keeps you from bleeding the accumulator while purging the air.

Not necessary for the auto bleed.
Good point, but I've found when I bleed this by unscrewing fittings it fixes itself almost immediately. Then again, when I unscrew the fitting I first shut the accumulator valve (isolate the accumulator).
 
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Jim26m

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Apr 3, 2019
579
Macgregor 26M Mobile AL
That would work almost as well as the check valve. The check would just prevent system drain back too.
 

Jim26m

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Apr 3, 2019
579
Macgregor 26M Mobile AL
One last thought, then I'll quit bothering you.

That vertical 5 ft dry lift may be with an open discharge.
 

jviss

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Feb 5, 2004
6,745
Tartan 3800 20 Westport, MA
Jim, I want to thank you for all of your help on this, you are quite thoughtful and considerate. I really hope I can solve this. It's amazing to me that I haven't come across some marine plumbing standard or best practices yet. Fingers crossed!
 
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Jim26m

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Apr 3, 2019
579
Macgregor 26M Mobile AL
Agree. Always better when you can get more definitive info. I can't even find a good description of vertical dry suction lift for that pump either. The brochure doesn't mention any limitations on it though. There is an impeller pump by xylem that clearly states back pressure will prevent it from self priming. Otherwise, it will dry lift 6ft with open discharge. But the don't say that for the jabsco pump.

I never had to do a dry lift system, so I'm enjoying some new research. Thanks for sharing the issue.

If you had room to move the pump to below the manifold, that would put you back to flooded suction operation. That would likely take care of it.

You'll get it. Let us know when you find the silver bullet.
 
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Jim26m

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Apr 3, 2019
579
Macgregor 26M Mobile AL
Had one more suggestion to throw in the soup. A valve bypass allowing you to dump the accumulator charge back to the suction line/tanks. Eliminates wasting water during purge, and should allow pump to prime.

 

jviss

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Feb 5, 2004
6,745
Tartan 3800 20 Westport, MA
Thank you. That's a good idea, too. I think I'm going to try the air vent first. Then, I was thinking, I'd like a garden hose bib in that locker, for times I want to rinse stuff with fresh water; it would serve the dual purpose of being a vent when this stuff happens.
 
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Jan 22, 2008
8,050
Beneteau 323 Annapolis MD
From the original post, when you shut off the accumulator, do you epen a faucet to let air out. Sounds to me like the accumulator had alreay pressurized the pump output with air, and awater can not pass through. The accumulator is back-pressurizing the pump?y 2 cents.
 

jviss

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Feb 5, 2004
6,745
Tartan 3800 20 Westport, MA
I've tried that, Ron, to no avail. Maybe I didn't wait long enough, but I didn't want to waste a lot of water, nor burn out the pump motor.
 
Jul 1, 2010
962
Catalina 350 Lake Huron
This doesn't exactly fix the issue, but could you pressurize the tank at the fill fitting (you would have to close off the vent) with a hand pump (maybe one for inflatables). That would probably get the prime started without having to tear into the cabinet and disconnect hoses.
 

jviss

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Feb 5, 2004
6,745
Tartan 3800 20 Westport, MA
This doesn't exactly fix the issue, but could you pressurize the tank at the fill fitting (you would have to close off the vent) with a hand pump
Thanks! But not really practical, but I don't think it would solve the problem, anyway. There will still be air trapped on the output side of the pump.

The hoses are all easily accessible in the port cockpit locker.