Home · Cleaning · Best practice · Condensate trays, drains and biofilm
Cleaning best practice
The short answer
A cooling coil produces water, and the tray and drain that carry it away are warm, dark and wet — ideal for biofilm, which is where AC smells usually begin.
Most complaints about an air conditioner that smells are not about the ducts at all. They are about a few centimetres of standing water below the coil.
How it is done
- Clear and flush the condensate drain rather than only wiping the tray.
- Check the fall on the drain line; standing water means it is not draining.
- Clean the coil face, where growth takes hold first.
- Look for water staining on the ceiling below, an early leak sign.
Why it matters
Left alone, a blocked condensate line eventually overflows into a ceiling void. The smell arrives months before the damage does, which makes it a useful warning.
questions
Asked about this
Because the biofilm was killed but not removed, or the drain still holds water. Mechanical cleaning and proper drainage are what make it stay away.
Legionella is chiefly a concern in water systems and cooling towers rather than split units, but any warm standing water deserves attention.
references
Background reading
- Biofilm — Wikipedia
- Legionella — Wikipedia
External encyclopaedia entries for the underlying concepts. They explain the science; the practice above is how we apply it in UAE properties.