I tried buds first. then a scourer. Then I cut a small piece apart and tried a knife to scrape it. Clearly the discoloration is internal to the tubing and it cannot be removed. It appears to be part of the tube itself now.
The stangest part is - where the tubing fitted over connectors it has remained clear (Transparent) and clean. The rest of the system parts (Blocks, connectors, etc) are all clear and clean.
I have only used Koolance Tubing and I only have Koolance tubing in my stock.
I made a huge mistake a few years ago and bought a Gigabyte Mercury Case with in-built cooling IT WAS MY FIRST WATER COOLING. I got hooked on Liquid Cooling and really enjoy building the systems and setting them up. Within a couple of months I was looking at what was out there. After many months and reading all the huge contaversy about Koolance products back then I happened on some Koolance stuff at a friends place and soon I spent a wack on Koolance - it is quality stuff - and have been with Koolance ever since. As soon as I got my kit I stripped the Mecury case and played - That system is still running today and beside cleaning filters and fans it is spotless and clean.
I have only ever bought Koolance myself, although others I have helped build have bought other stuff and some of it is also good stuff (In january I was given 2 EK Memory cooling blocks as gift - they are the first Other I have ever owned) and I am about to put them into a new build. Not neccesary but they will look good I think.
I have not really done much - built a few for myself and also for a few friends and helped others build. Mostly They go with Koolance first and then off on their own they break, flood, burn and cry.
The discoloring is internal to the tube and cannot be scrapped away, boiled away or wiped away. Neith can a multitude of detergents remove it. WHAT MUST BE NOTED is that the system blocks and connectors and radiators all appeared to be spotlessly clean and in good shape when dismantled - It is just the tubes that are not.
ANOTHER STRANGE THING IS - where the tubing fitted over connectors etc. it is still as clear (transparent) as it was the day it went on... ???? Only where the UV Blue liguid flowed is discolored. Also the system had no UV lights in it.
I got really pissed by the absolute palm-off by Koolance Tech especially the first response - change the liquid as soon as you see color change. Heck I went into emergency shutdown
All I wanted was some supportive direction or pointers and I got zip. A mountain of it could be, but never seen in Koolance products - that may be - all I want to know is what went wrong here or find out what is going on.
Hope the Lab comes up with something - but I get a lot of mouth around here and little action on just about every front - but lets see.