Alarms such as you mention are familiar to many folks in the Poconos. There they have to do with dousing tanks, following the gravety fed holding tanks (septic tanks), that fill about 25% and are pumped into elevated drain fields (locally called "Turkey Mounds"). If the pump fails to empty the tank, a separate alarm circuit goes off in the basement when the tank is 75% full. Likely you have a pump or wiring problem!