I got a free Poland Spring 5 gallon water cooler from work.
We've been using the cooler for years, but they got a new one....

I took and home and tried to clean it up, in order to clean it up to meet my wife's cleanliness standards.

As I inspected it, I noticed that there is a brown film/staining on the plastic components of the cooler (in the resovoir, on the plastic baffle in the resovoir). I also unscrewed the hot and cold spigot handles and there was the brown film/staining in there too. It kinda looks like mineral deposits/staining.

It comes off when i run my finger across it....but i can't get my finger in all the nooks and crannies where the staining is.
So, I ran boiling water through the unit. I let the boiling water sit in the unit for over 20 minutes. But that didn't get rid of the brown film.
I tried vinegar and hot water....no luck....
I tried bleach and hot water.....no luck...

Does anyone have any suggestions for clenaing up the brown stain/film?
Or should I not be worried about the staining? Is the stain/film mineral deposits from the bottled water?

thanks.
mike