We use Harbor Freight $10 water leak alarms to let us know if there is water in an area that should be dry. Water Overflow Alarm (http://www.harborfreight.com/water-overflow-alarm-92334.html)
Good areas to monitor for water leaks are behind toilet, water pump, water manifold, dump valves, behind fridge, hinge side of bottom step. Alarms have saved us several times.