My BIL who sells commercial units told me to put a couple of pennies in the pan near where it drains. Seems to kill whatever was growing in mine.
Actually, this is a good unexpected post.
Maybe even more effective, not knowing how much copper is in pennies anymore.
Get a short length of copper wiring and strip it down to the copper. Enough copper in the system will kill bacteria.
On our last house that had two units what I did was from outside the house with my hand, hold the garden hose up against the pipe and reverse flush it but not too long, so it would overflow the pan up in the attic, then the water would rush down the pipe and take out whatever junk was in it
We had two drain lines one for each unit.
That’s all that took for 16 years.
We are now going on our third year in our new coastal home and come to think of it. I never flushed anything yet.
However, if I don’t use the above method, I would just probably pour a couple caps of bleach in the plastic pipe up in the attic, but not in the pan.
I might have to rethink that with a nice thick piece of copper though
