Pressure tank is empty

[DerekA]

I have a deep well with jet pump feeding a small 8.5 gallon, horizontal, pressure tank. In the cold weather lately I have on two occasions now had a minor freeze up which I determined to be in the small pipe leading to the pump switch. A few minutes with a fan heater has fixed it, and everything seems ok thereafter. Today though when I did this, I noticed that the pressure tank seems to be empty - there is no weight to it. But everything else seems to be ok. Taps run, and the pump goes on periodically for maybe 30-60 seconds at a time, though I haven't checked this thoroughly. The pressure gauge seems to be showing normal activity between 25 and 45 psi.

Why is the tank empty, and where is the water pressure being stored? In the well maybe, or the hot tank? Other than the filter, there are no other tanks in the system. I'm at a loss as to how to proceed, other than call a plumber which I really can't afford right now, so any help would be appreciated.

 

[Valveman]

If your pump is running 30-60 seconds between 25 and 45 PSI, then the tank is taking water, but your pump isn't putting out much. An 8.5 gallons size tank only holds 2 gallons of water, so it feels empty even when full.

The pressure is stored in the 6 gallons of air that is used like a spring to push out the 2 gallons when you need it.

 

[DerekA]

Thanks for your response. It's encouraging, but I'm not sure what is implied by 'pump isn't putting out much'.

I will check the weight of the tank again. I don't recall it feeling like anywhere close to 2 gallons (20 pounds) when full.

 

[Valveman]

If the tank holds 2 gallons and it takes 30 seconds to fill to 45 PSI, the pump is only producing about 4 GPM.

Let the pressure build to 45 PSI and the pump shut off. Turn off power to the pump. Then check to see how many gallons you get out of that tank.