A leaking rooftop AC unit on your commercial building is more than just an HVAC problem. If it isn't addressed, you may also have a roofing and structural problem.

Symptoms and Problems

Standing water and leaks are the most obvious symptoms of AC water issues. Your maintenance crew may discover damage to the roofing membrane around the AC unit, which is caused when water seeps beneath the membrane and causes adhesion failure. There may also be standing water on the roof near the unit or mold and algae growth inside the unit itself.

Inside the building, the most likely symptom is water damage. Water stains may appear on the ceiling directly below the rooftop AC unit. The insulation in the ceiling below the AC may also get wet, which can lead to mold and mildew growth in the insulation. Another major issue is water damage and rot, which can weaken the roof below the AC, leading to structural issues or even a roof collapse.

Common Causes

The most likely cause of the leak is a blockage somewhere in the condensate system. Usually, it is a matter of debris getting stuck or biofilm and algae growing inside the condensate drain line or in the drain pan itself. This forms a blockage that won't allow the natural condensation that forms to drain away from the roof properly, and instead, the drain pan overflows and causes water damage to the roof.

Other issues include damage to the condensate pump, which means that the collected condensation will collect in the unit instead of being pumped into the drain line. Clogged filtration systems and dirty AC units can make matters worse, as they will be prone to producing more condensation compared to clean units. 

Repair Methods

Repair typically begins with the condensate drain system. The pan will be inspected and the drain opening cleared. If the pan is damaged and leaking, it may require replacing. A blocked line may be replaced or cleaned out, depending on the severity of the problem, then your repair tech will ensure it routes the moisture safely away from the roof. 

If the pump isn't working, it will be either repaired or replaced. Then the unit will be completely cleaned out and the filters will be replaced so that the unit can run efficiently with the minimum amount of condensation production possible. 

Contact a commercial AC repair service if your rooftop unit is leaking water.