Pump losing pressure mystery

[sjc]

I'm using a General Pump and feed the water to the pump from a tank (gravity fed). The pressure is dropping off significantly after the water level drops (even just a foot or so) in the tank. I ran a garden hose to the pump and the pressure was excellent. I redid the plumbing, and replaced the valves and packings and it made a difference for about a month, but now it is worse than ever (though still excellent when water is pressure fed to the pump).
I have checked all filters, and the water flow is not restricted.
What else could be causing the problem?
Thanks for any suggestions.
Stephen

 

[north coast]

Is it a belt drive or a direct drive? Sound to me like it is a direct drive which would need a pressurized water source. You may need to add a small 12v pump to supply the pump from your water tank.

 

[Mark]

What size hose are you running from tank
to pump, and how long is the run.

What model General pump?

 

[DAFF]

Sounds like a suction or air lock issue. Gravity feed pumps will work great under normal conditions, check hose for a small pin hole on the suction side(pump to tank). Are you using a water screen? If not you could have a piece of debris stuck in one of the intake valves(bottom side of pump). Do a simple check by pulling off the cap and using a needle nose plyers to pull out the valve. Check that it seets correctly and the O ring for wear (inside the hole).


GOOD LUCK

DAFF