House is spring fed and pressure is assisted by a pump mounted atop the pressure tank. The pressure switch is a 30/50 and the pump is cutting off at 45 and back on at 40, this occurs about every 30 seconds. The water has not been used for several months, the air pressure in the tank was low (about 15 psi) so I added air to bring it up to 28psi. and that did not help. The air pressure has held at 28psi for the last four days. I replaced the pressure switch and there is no difference. I have checked the lines for leaks and cannot find any. I would appreciate any suggestions to help with this problem.