What's "spring". We use A/C most of the year here. It is the heat that only
gets turned on a couple days a year. :-)

As for the drain line I am only repeating what I have heard. My wife worked for
the biggest Trane dealer in the 3 county area for 5 years and another dealer
before that so there are a lot of people who are doing it wrong here.
The company that she works for now, building houses, is saying the same thing
although the rich *******s who can afford her houses won't be doing anything to
their A/C units except telling the maid to turn it down.
I know bleach is nasty stuff but people do sling it around a lot here for mold
and mildew.
I even see people using pool chlorine which is double strength bleach. Tilex is
between those.
Roughly 5%, 7.5% and 10%
I certainly agree you don't want this on metal, any metal. My wife toasted some
"lifetime guaranteed" Delta faucets with Tilex. Delta replaced them anyway.
I will pass this on and see what the local HVAC guys say.