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Fresh water pump runs continuously

Mikebat

Member III
My fresh water pump (ShurFlo, late 80's model) runs continuously if the breaker is on. It seems to have air on the pressure side, but I have bled at least 10 gallons of water through all the taps, and yet the air is still in there. I checked the intake strainer today, and saw that it had a bunch of bubbles bouncing around inside it when the pump was running. Pulled it, cleaned it, and found a crack in the hose barb base. So I replaced it, tried to bleed the system again, and now there are no more bubbles visible inside it, but the pump still runs continuously and air+water is still coming out of the galley cold water tap, and the head cold water tap. Both hot water taps seem free of air. I guess this is because the hot water tank collects any air in the lines, but the cold water taps are connected directly to the pump outlet, with no tank to collect the air.

I can't find any fresh water leaks while the pump is running. There is a very slow drip of water coming off the pump body while it runs (can't quite tell from where), but it's hard to imagine that this is enough flow to cause a pressure drop and keep the pump running. It might be enough to introduce air, however. I wonder if I need to pull the pump and replace the diaphragms? Or maybe it's the pressure switch that's busted? Any other ideas?
 

cruis-n

Member II
Freshwater Foot Pump

If you have a freshwater footpump plumbed into the supply from the tank that also feeds the pressure pump, this could be the source of the air. Sometimes the pressure pump can draw just enough air through the footpump spigot to cause the symptoms you describe. Try placing your finger over the footpump spigot while the pressure pump is running. If there is a vacuum, this could be the source of the air. If not, keep looking. I found a crack in the tank supply line to the pump that showed up as a couple of drips just as the pump was shut off (small back pressure when the pump shut off, otherwise just sucking air).

Hope this helps.

Paul
 

chaco

Member III
The Pump Switch !

Hi Mike,

Had the same problem on my 74' E35-II.
Replaced the switch.....same problem....
Alas! I finally figured it out.
The diaphram that operates the switch was to close to the switch (on).
I had to shim the switch away from the diaphram with nylon washers.
And...the most important part. Your pressure tank needs to be inflated
to the turn on pressure of your unit (on 20-30psi / off 40psi).
Put a pressure guage on your tank and watch the cycle.
Inflate the tank to the pressure that activates the pump.
Shut er' down and inflate the tank to that pressure with a bicycle pump.
This will get you up to operating pressure sooner without the long pump
cycle. Check the tank again the next day for LEAKS ! If the tank does not
maintain pressure under static (off) condition the the tube inside the tank
leaks.

good luck

dan :egrin:
 

erobitaille

Member II
Mike,

I had the same problem on my E-381. Chased it for two weekends and found the same as Paul. THe foot pump would drain and leave an air gap. I just installed a PVC ball valve form Home Depo on the foot pump line and everything works fine. It did take what seemd like a long time for the pump to get all the air out of the system. Pumping the fresh water foot pump at the same time helps. :egrin:
 

CaptnNero

Accelerant
I have an '88 E34 originally with a Shurflo.

I didn't have the air problem but the diaphram in the pump needed to be replaced last year. It pumped but not enough pressure to depress the cutoff switch in the pump. So after an exhaustive search I found it was out of production and the spares market was dried up. Funny thing, the manual said if the switch stops working, just cycle the power switch.

A hundred bucks later I swapped in the latest model and it works fine.

-- neal
 
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