Trying to help a single mom. She has a shallow well (28' she says) used for a sprinkler system...Very old Sta-Rite. Can't read the HP, but probably is 1. I replaced the broken tank (small), re-sealed all connections, blew out the pressure line from the pump to the NEW 30-50 Square D, and set the 'on' pressure to 28 PSI. Problem NOT solved. No pressure guage on the pump, but its water flow is strong, so, the pump PSI has to be well above 30. I lowered the 'off' pressure as much as possible to where it had to be at or slightly above 30 PSI. Then the Square D contacts would rapidly open and close (off/on/off/on, etc.). Will welcome any suggestions.