My reservoir managed to stay clear for a remarkably long time running nothing but distilled water. I originally flushed once overnight with a full bucket of tapwater and a whole bunch of milky/oily crap came out.

I decided to add some zerex and almost as soon as the zerex hit the water (which was completely clear) it went milky :| The Zerex in my bottle is transparent purple.

I have a PA120.3 btw and only copper components.