Water alarm for monitoring floor moisture

Claim 1

A self-contained water alarm for monitoring floor moisture comprising: a housing having a plurality of support feet for supporting the housing on a floor with the bottom of the housing in close spaced relation to the floor; a plurality of pairs of printed circuit sensor electrodes, each electrode pair being mounted on the outside of the bottom of the housing in a position protected from floor contact by the support feet, the sensor electrodes of each pair being in closely spaced relation to each other immediately above the floor on which the housing is supported, the resistance between the sensor electrodes being very high when the floor is dry and much lower when the floor is covered with water to a depth sufficient to contact the electrodes; an electrically actuated audible alarm device, mounted within the housing; battery mounting means for mounting a battery within the housing; and an alarm circuit, mounted within the housing and interconnecting the alarm device, the battery, and the sensor electrodes, the alarm circuit comprising: a solid-state switching device, connected to each pair of sensor electrodes and actuatable from a normal non-conductive condition to a sustained conductive condition in response to a low resistance condition between any pair of the sensor electrodes, the switching device having a main discharge path connected in series with the alarm device and the battery; and an auxiliary pair of sensor electrodes mounted on a small pad and electrically connected in parallel with the housing-mounted pairs of sensor electrodes through an elongated extension cord to permit simultaneous monitoring of floor moisture and of the water level in a sump or in a standpipe, the housing including a storage compartment for storing the auxiliary electrode pad and cord when not in use.