Make sure your tenants don't use harsh chemicals  to clean the tub or any of the liquid drain cleaners!

That's what they do all day and typically are good at, not to mention all the different chemicals and whatnot involved with this.

Consider an environmental study due to contaminated waste and chemicals used in the medical field.

But first I would make sure it is operating on a salt water system, no chemicals needed, just add salt which the the cleaner will take care of.

I assume you are based on your price, but if that's just chemicals you are getting hosed.

Dry cleaning stores seem to pose a whole new set of problems due to the chemicals they use that can seep into the ground and contaminate residential water supplies. 

; unusually higher rainfall recently; changes in the occupants water use, laundry use, food/drinks, chemicals; a sock or something flushed down the drain; a combination of these or something else.

I am able to admit if I am making mistakes, and maybe I do need to be a little harsher when it comes to giving notices.  

My name is Akash and I graduated college 4 months ago as a chemical engineer from UCSD.  

We continue building in unsafe areas, injecting toxic chemicals into the ground, poising our environment with petroleum based products, extinction of plant and animal species, and enslaving and killing each other.