A standing water alert system comprises two conductive wires or a float extending into a drain and connected to an audible or visual alarm that is triggered when standing water is present. A drain alert system and method comprises a plurality of sensors, such as pressure or acoustic/vibration sensors, at various locations within a plumbing or fluid filtration system to measure pressure or an acoustic profile at that location and a control system to compare the measured parameters to a threshold value or range and/or to other measured parameters from nearby sensor locations. A signal is sent to a remote user or computer or an alarm is triggered when the comparison shows a potential blockage, a leak, or indicating that a filter needs to be replaced or cleaned. An approximate location of the blockage, leak, or fouled filter is determined by comparing measured parameters at nearby sensor locations.