Pressure pump with tank on @30; off @50psi. Builds pressure fast, loses it fast as well. Why? What to do?

Question

After observing pump operation for about 30 minutes: average time to build pressure from 30 to 50 psi = 17 seconds. Pump stops, sort of hissing sound inside, though no air coming out of it; pressure drops fast to 30 psi in about 2 minutes, even if there's no open tap. Pump gets water from a big tank, then pumps it into pressure tank. Taps get water from pressure tank. I think it's just ordinary pressure tank, not bladder type (whatever that means). Previous problem: slow pressure buildup, fast pressure drop, so before switching it on, I tried making sure enough water inside pressure tank, though can't be sure how much due to no sight glass. Now this problem. Please help.

Answer 1

Sounds like you have 2 problems. One is free and easy to fix and the other is costly and easy to explain.

Free and Easy: The pressure problem is caused by a waterlogged pressure tank. Make sure the pump is turned off, first. Open whatever valve you need to to drain the tank completely. You may find a small pressure relief valve on top of the tank. In the valve should be something like a valve stem on you car's tire. You will need to open the relief valve to allow the tank to drain completely. Then all you have to do is put everything back, close the valves and turn on the pump. The water pressure compresses the air inside the tank and serves as a steady pressure supply tank.

Costly and easy:

The seals inside the pump are shot, replace the pump.

Answer 2

What has been said about the pressure tank so far is correct, and you should have a small air cushion in the tank to help hold pressure. But I don't think that alone is your whole problem. You said that when your pump brings the pressure up and shuts off, you lose pressure even though you are not using any water. This would indicate either a leak somewhere (which I assume you would have been able to find) or a faulty check valve between the pump and the pressure tank. A faulty check valve could let water bleed back through the pump and back into your source tank. Could be dirty or worn out. Look into replacing this valve.

Answer 3

Your pressure tank should have an air cushion inside. If it doesn't have a bladder you have to get air inside. See if can see what looks like a bike valve. You can charge the line with about 30 pounds of air.

If all else fails,shut the pump off and drain all the water out your tank through the tap. You may get some air into the tank that way.