Primary drain pans inside of HVAC units discharge approximately 8 to 12 gallons of condensate per day during the summer months and often become clogged after years of service. Secondary drain pans are usually installed under these units when they are placed in an attic or above living space. When standing water is found in the secondary pan, this is an indication the primary pan has either failed or become clogged. The secondary pan should either have a drain line extending to the exterior of the building or a shut off float switch installed to shut down the unit to protect from any possible water damage.