i have a deep well with a 1/2 horse power jet pump and a 38 gal pressure tank my problem is my pressure tank isnt filling with water i have water in the house but only running from the pump, the pump runs constantly at first i thought it was the pressure switch put on a new one but no improvement. the presure gauge is reading about5 psi and the pressure tank is real light. it is set for 20\40 i checked for water log problems but no water coming from air valve. tank pressure at tank when empty is reading 18 psi 2 lbs below cut in pressure? what can cause this problem