The majority of the rentals are chemical plant employees and most construction has been delayed.

I know that we don't have the best water because of lead and other chemicals. 

Your ac condenser and evaporator coil were not designed for different mixtures of crappy Chinese refrigerant and the two different chemicals will react. as all chemical compounds do when you mix them.

@James Lord My grandpa was on the chemical engineering team that patented these!

I tried multiple chemicals including Comet to remove it, but didn't worked.

Do you guys have your cleaning service take care of rhe cleaning and chemicals?

I have also asked her to send me information of what chemicals she used to bomb the unit as well as dates.

Cheaper options include using chemicals like Odoban or trying an ozone machine to clean the area.

You couldn't be bothered to use a 50-year-old weed control chemical on an overgrown yard because you believed some quack somewhere that told you it might cause cancer.Now you're hypothesizing that your dirty tenant brought a breeding population of rats with him.Come on, Peter.

I live in the CENTER of 6 major chemical plants including BASF, Dow ,BP... the rental market here is KILLING IT, because you have the average Joe making 75-125k a year!