I have had both a dehumidifier and a mini-split HVAC unit plug with slime mold already this summer. The mold forms a gelatinous coating in the condensate tray which eventually plugs the drain line. Water spilling out onto the floor is the obvious indication of the problem. For the mini split, the cure is to suck the tray empty using a wet-dry vacuum at the discharge end of its condensate hose. I used a rag around the condensate hose to get a tight seal. Then remove the front cover of the inside unit and fill the condensate tray with a dilute mixture of chlorine bleach (Chlorox) and water to kill the mold. Let it sit awhile then suck it out. Repeat as necessary. I was lucky this time to catch the overflow before any damage was done.

The dehumidifier (Hisense) has a pump to automatically remove condensate to an outside drain. There is a filter on the suction side of the discharge pump that plugged solid with mucus-like slime. It was gross. Bleach solution and a soft toothbrush cleaned it. The indication of the problem for this brand of dehumidifier is that the bucket fills up and shuts off the unit. Wish the mini-split had the same feature.

I have had condensate drains at various houses and condos plug before. Routine maintenance is expected, but it takes years of neglect to plug it up. The remarkable thing at the shop was how fast the plugging occurred. We are just half-way through the humid season. The dehumidifier was new last fall. The mini-split had its seasonal service less than a month before it plugged. It has only been in service for less than a year. It was a new HVAC tech who may not have cleaned the drain.

I suspect that wood dust is providing food to the mold making it grow faster in the shop than in my house. We have also had a record year for pollen and mold in the air. I think it would help to use my air cleaner’s programmable feature to run the filter occasionally when I am not there, change air filters more often, and schedule drain-cleaning twice a summer.

Hope you all take a moment to pull the front cover of your units and clean as necessary.