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post #1 of 6 Old 07-05-2012 Thread Starter
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Troubleshooting Fresh Water System

Hello fellow boaters

I have a Jabsco model 36800 electric fresh water pump and need help understanding where to start troubleshooting my problem

After initial priming the system, when I run a facet the pump runs fine and shuts off. But after not using the water for a period of time, when I run a facet, it starts out fine then losses pressure and starts to spit air. then the pump does not shut off until I "re-prime" or let the pump come back to pumping water and no air.

any ideas?
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post #2 of 6 Old 07-05-2012
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Re: Troubleshooting Fresh Water System


It sounds like the pump is drawing air. Have you serviced the water system recently? Have you changed filters or anything like that? If so, check what you did first. If not, you'll have to check each fitting, from the tank to the pump. I had a similar problem a few years ago. It started right after I cleaned a strainer before the pump. When I put the strainer back together I tightened it too much and cracked it. The crack was very fine, but enough to let air into the system and the pump would never turn off because of that.


Good luck,

Barry Lenoble
Deep Blue C, 2002 C&C 110
Mt. Sinai, NY

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post #3 of 6 Old 07-05-2012
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Funny, I had a similar problem a number of years ago. Check the inlet side of the pump make sure water is running freely to the point of the pump, ie make sure nothing is restricting the water from the tank. I actually found a butt connector stuck in the water line.
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post #4 of 6 Old 07-05-2012
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Re: Troubleshooting Fresh Water System

do you have a vent on the tank? if not, crack the fill cap on the tank slightly.

It's 5 o'clock somewhere:

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post #5 of 6 Old 07-05-2012
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Re: Troubleshooting Fresh Water System

We just dealt with a similar problem. We noticed after de-winterizing that we had intermittent spitting of air (but not always!); pressure variation, at times quite low, then would flow with more pressure, then repeat; and unless water was flowing really well, pump would not shut off (prime). With all these symptoms, and no obvious water leak or visible problem with system, we were stumped and thinking we had to replace the pump, or pressure switch was shot, or debris in pump... our research made the possibilities seem endless.
Then, thinking it through led us to realize that just because no water is leaking out, air can still be leaking IN. Start with that. We have two tanks, with two runs of hose (with a strainer each) into our water pump. Because we did have the "spitting air" symptoms, we thought we should consider that as the cause first. We looked at both strainers for loose cover or hose fitting or a even a crack. nothing. Then, my husband tightened each clamp on the hoses connecting to the water pump from both water tanks. just a little tightening. VOILA !! System is now working fine, no air spitting, pump shuts off like a charm as soon as you shut off faucet. Pressure is consistently good! All our problems seemed to be caused by a minimally loose hose fitting. Because we have two tanks feeding the pump, and a line that extends to galley sink, head sink, bow washdown and stern shower, we were overwhelmed when considering how to troubleshoot this situation. LESSON LEARNED: start with the simplest (and most likely) cause first. Start from your tank(s) and tighten the clamps and inspect each connection. Just because you don't see a leak doesn't mean that air isn't leaking INWARD. Don't make our mistake and jump to the worst case scenario that pump is shot! All of the symptoms we had were ultimately caused by a leakage of air into the system, before the pump. Check that first! and Good Luck.
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post #6 of 6 Old 07-06-2012
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Re: Troubleshooting Fresh Water System

Just answered this question on a similar post. If you have both a manual pump and electric pump using the same water line from the tank, you must close the valve to the manual pump to prevent air from being drawn into the system. It worked for me.

Good Luck,

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