Abstract: A drain overflow alarm for a washing machine drain, which alarm is mounted in a vertical drain line offset provided with a check valve and extending from the vertical fixed drain line or standpipe of a structure. In a preferred embodiment the alarm includes a float switch located in the top end of the drain line offset and a transformer, relay, alarm and optical reset button, all provided in a control housing. The float switch is electrically connected to the transformer, relay and alarm, such that obstruction of the fixed drain line causes water to rise in the fixed drain line and through the check valve into the drain line offset. The rising water raises the float element of the float switch and closes the switch to activate the transformer relay and alarm, as well as terminate operation of the washing machine.

Abstract: An air conditioner drain blockage alarm system which is designed for application to both horizontally and vertically-mounted heating and air conditioning units, which alarm includes in a preferred embodiment, both a normally open drain line liquid level switch and a normally closed drain pan liquid level switch for sensing blockage of a drain line in both the drain line itself and in the condensate drain pan which collects condensate from the air conditioning unit. In addition to the drain line and drain pan liquid level switches, the system is characterized by an alarm which audibly indicates a high water condition in either the condensate drain pan or the drain line and a manual override switch for manually silencing the alarm. In a preferred embodiment, the system is wired through the existing thermostat in the heating and air conditioning unit to facilitate deactivating the air conditioning system by the drain pan liquid level switch when the condensate drain pan is subject to overflow.