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Old 03-23-2015, 10:31 AM   #1
MYTraveler
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City: West Coast
Join Date: Apr 2014
Posts: 1,790
Holding Tank Problems

My 100 gallon holding tank is pumped overboard by a Whale Gulp diaphragm (good thing for spell check, or I would have left out the silent "g") pump, which takes 20-30 minutes. During the last 6 years the diaphragm broke once, but otherwise no problems with the pump.

However, on two or three occasions, despite pumping for 60 minutes (by design, the pump can run dry without damage), the gauge continued to show full. I wasn't sure whether the gauge was bad or the pump had failed to pump. In both cases, I left the pump on, flushed the heads a few times, and ultimately the gauge showed empty.

Well, it happened again yesterday (with the gauge reading 3/4 full), so I added water (through the heads) until they wouldn't flush any more. Then, about an hour later I noticed the gauge was down to about 1/2 full, and 10 of 15 minutes after that, it was showing empty.

So, I suspect a "blockage" (the pump draws through a 1-1/2" tube that draws from the bottom of the tank), that resolves itself over time. Has anyone experienced this? Any suggestions?

I have two ideas. First, I may put a clear section of hose (probably after the pump so that the pump's suction doesn't collapse it, so I can see if it is pumping. Second, I may put a T-fitting and valve in front of the pump so I can force water backwards into the system. I am also thinking of putting a second valve so I can force the water through the diaphragm pump -- I don't see how that could damage it, right????

Any thoughts, suggestions, etc., greatly appreciated.
-Rick

One detail that might be worth mentioning -- my boat has a separate holding tank to service the day head. Same exact set up -- same head, same macerator, same type tank and draw pipe (different dimensions, 40 gallons vs. 100), and same diaphragm pump. This head has never had a problem.
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