Moe Jones wrote:

"Phil Again" wrote:
After a couple people made similar comments, and seeing similar stuff
on the web, I managed to find the piece of code for my locality
(Montgomery County, MD). Turns out you're not allowed to discharge
AC condensate into the sanitary sewer system.

It is not allowed because if the drain goes dry then you could suck sewer
gases into your home.

That doesn't apply if the condensate drips into free air space before
trickling into the sewer drain. In fact, it can help ensure that a
seldom used drain trap doesn't run dry.

I know of an instance in an office building where a return air plenum
access panel was inadvertently left open, creating negative air pressure
in a fan room where the floor drain trap was dry. The result was sewer
gas being distributed throughout the building. Phew! That might not
have happened if condensate was going down that drain (and if the HVAC
tech was more conscientious).