Water tubing turned green

Yesterday I had to access the back of my 50w laser and noticed that the water tubing has turned light green. I thought it was odd, because I have a CW-3000 chiller and the water level tube on the front panel that I check for any discoloration is perfectly clear.

Went inside the laser tube compartment and all of the tubing inside is also green, but the laser tube looks fine. I dumped the water expecting to see nasty algae filled slime water, but it looks perfectly fresh. The green can be rubbed off, I wonder if it’s some chemical reaction of the silicone itself, but in all of the years working with water chilled lasers, I’ve never had just the tubing go green. I’ve added a bit of bleach to a gallon of water and will let that cycle for a day just in case.
Has anyone else run into this?

Doesn’t look the color of algae.
Does look the color of corroded copper or brass. Any fittings that could be suspect?

Where did you get the water?

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I’m thinking the same as Hank, that it’s copper corrosion. And just in case you don’t know, the CW3000 is NOT a chiller, it is just a radiator with a fan blowing over it so if you are using this on your laser and you are not in an air conditioned room with room air temp set below 25C you will be running your laser too hot.

Also, did you use distilled water? Not de-ionized or filtered but pure distilled water is what you want to use.

You are exactly right, it looks like copper oxidation, the radiator has copper tubing throughout. The odd thing is that it only stuck to the tubes that came with the laser. I opened up the CW and all of the tubes inside of it are squeaky clean.

Yeah, the CW3000 is not ideal, I got it for a decent price and will be modifying it with with an array of peltier modules to get actual refrigeration going. Even like this, it’s been working fine, I’ve never seen it go above 25 degrees, usually stays at consistent 23.4. The water is plain distilled, at least that’s what it says.

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Yes, I have had the very same issue. I think it is due to an issue with the tubing itself. BTW, bleach didn’t clean it out for me.