What is the white stuff leaking from my AC indoor unit

Most commonly it's water from your AC's condensate drain line backing up or the drain pan overflowing. This is not an emergency. AC systems produce water as a byproduct of cooling and drain it through a small pipe or pump. When the drain clogs with algae or dust, water leaks into your home.

How to check the drain

Locate the small drain line from your indoor unit, usually a half inch plastic or copper pipe. Follow it to where it exits your home, typically at a basement window, crawlspace, or exterior wall. If water is backing up inside, the line is blocked. Clear the drain by flushing it with a wet or dry vacuum, pouring bleach solution through it, or using a plumbing snake. If you see clear water with no odor, this is safe to handle yourself.

When to call a technician

If the leak smells sweet or oily, it's refrigerant, not water. Stop using the system immediately and call a technician the same day because refrigerant leaks require professional repair. If you see wet yellow, pink, or blue material that looks like insulation, stop using the system and call a technician because this indicates fiberglass contamination in the refrigerant loop.