Shallow jetpump with airtank, runs near empty before pump runs

[educateme]

I had to depressurize and drain the system to replace a leaky drain spigot on the bottom pipe running from my airtank. I pressurized the air tank to 38psi as part of the refill and priming process, my switch is a 40/60 on Sears 3/4hp shallow jet pump to 15 ft well.

When the pump is primed it pumps strong water right away, but if it rests too long near the lower end of the pressure at 40psi, it has trouble getting water flowing right away from a faucet.

It seems the airtank is nearly empty sounding when I bang on its side at 40psi, and the lack of much water in the pipes, or tank at 40psi makes the jetpump labor to get water to self prime quickly to pump back into the tank and pipes up to 60psi. It runs 2minutes to get to 60psi each time it cycles down to the low 40 psi. This is not how it used to work.

It seems the tank should have more water in it at 40psi, and keep a steady amount of water in the pump system and pipes leading from basement to upstairs house faucets.

What should I be doing to correct the lack of water in the tank at 40psi, is there a setting on the pressure switch, airtank, or a way to raise the water level in the tank so it runs and pumps easier, without starving the pump when it drops to 40psi. The pump sometimes puts bubbles in the water as it cavitates when cycling, but it always manges to pull thru after about 10-20 seconds of laboring sounds.

[jadnashua]

Your tire pressure gauge may be reading different than the pump control switch's gauge. With the system pressurized, but nobody running water and the pump stopped, take the pressure reading on the tank. If it isn't the same as the gauge on the switch, compensate with your tire pressure gauge reading so you get the 2 pounds below the turn-on point - whatever the reading is.

[speedbump]

I think you have a screened well, and the screen is plugging up with minerals. That would account for the pump taking longer to pump up, and cause air bubbles. As the pump pulls harder on the suction line and screen, air is pulled through fittings that would would not leak under less vacuum.

Depending on the amount of calcium, magnesium, sulphur and iron you have in your water, gives the lifetime of a screen.

I'll bet that sears pump is even noisier when it's cavitating.

bob...