I’ve got the distilled water I need for the cooling system.

I’ve got the distilled water I need for the cooling system. But now I’m wondering about the white residue in the tubing that came with the K40 laser. Should I be concerned about it? Related question: it is in my garage and while it rarely snows here in the Seattle area, the temperatures can sometimes drop below freezing at night. Any suggestions to help mitigate freezing water destroying my laser tube? I know I cannot use anti-freeze. Would it be safe enough to blow compressed air through the tubing when I’m done to purge most of the water? How do you folks handle such situations?

You can try flushing the system a couple if times but personally I would get new tubing. I’ve seen where someone, in a similar situation to you, would keep the pump running and used a light bulb to keep the water above freezing. You could also probably use an aquarium heater with the pump running Just keep in mind to drain the tube if there is a power outage at the same time as below freezing temps. As long as most of the water is out then it should be fine.

I cleaned the white stuff from my tube by adding white vinegar to the water and letting it run overnight as recommended by @HalfNormal , worked great.

Thanks for the reply guys! Ok, so it sounds like this plan would be good: 1) just use some tap water mixed with white vinegar, run it through the system for a few hours, drain it (probably with some compressed air), then 2) put in the distilled water with about a capful of plain old Clorox bleach (to keep algae from growing) and run that for a while to make sure no bubbles are present, and in the meantime 3) order an aquarium heater that I can turn on if the forecast says the temperature might get too low. Sound like a plan?

I wouldn’t use the bleach…I use Tetra AlgaeControl

@Steve_Clark Why not use (a very small amount of) bleach? Please explain.

I live in Monroe and put a fish tank heater in my water with the pump. Both have been running 24x7 for the last 2+ years with zero issues.

@SirGeekALot Algecide has the least impact on the waters conductivity. I would expect that you will have to tilt the machine to remove the bubbles.

Here is the background: http://donsthings.blogspot.com/2016/07/k40-k40-s-tips.html

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@Jim_Coogan what’s the wattage of the heater you are using? 50W?

@SirGeekALot Don’s report is the reason. Thks’ Don.

Also be aware that bleach or vinegar could probably etch the inner glass surface of the tube when used for longer time. You would get blind glass like sometimes in a dish washer.

Don’s report is why I thought bleach was ok. I’ll get the Tetra Algae Control. It looks pretty cheap:

I have no idea why it says, “Robot Check”. That is the link to Tetra Algae Control on Amazon.

That’s the right stuff. I have no idea about the ‘robot check’ either. The link worked though.

The white stuff is as some have already pointed out probably lime / calcium carbonate from your hard tap water. It should go away with little acid (citric acid for preference). With higher temperature the precipitation will increase, so most fallout will be in/after the laser tube.
In the industry deionized water is often used for closed cooling solutions, but you have to be careful, because it could cause corrosion due to lack of buffering function of the missing ions. For the K40 , there are only glass, silicone/plastics and maybe a bit brass from couplings.
Since corrosion is no issue for our K40, the conductivity should also be no issue as long as you don’t throw in pure salt.

The microbiology will come automatically as soon as you have contact to the (non sterile) air, so even the purest water would not help as long as you could not guarantee a complete sterile cooling circuit. Algea will show up on bright spots (photosysthesis), so try to use opaque hoses and containers.

Bleach (containing hypochlorite) is also a good disinfectant, but comes often with detergents which could cause even more bubbles.
Also oxidative compound as clorine, ClO2, hypochlorite, peroxides will rapidly increase the decay of your plasic components!

My recommendation:
clean water (preferably deionized or softened) to avoid lime scaling.
Closed circuits for less ingress of dirt and microbiology
Dark/opaque tubing
regular water changes
fouling: anti-fouling biocides , algea control or (pure) disinfectants
bubbling: defoamers (e.g. siloxanes) or wetting agents

source: water treatment engineer

@Sebastian_C Good info, thanks! Regarding the white stuff, I have yet to run water through the system–the white stuff came with it. I’d also say they would have to be using some pretty damn hard water to make that much of it. So unless I got a heavily used laser tube (!) I think something else must be the reason for it.

In other related news, I have a brand-new 5 gallon bucket and lid from Home Depot, 5 gallons of distilled water, and some Tetra Algae control. I also have 10 feet of new silicon tubing from LightObject in case I feel brave enough to change the tubing. EDIT: Now I just need to find the time, which is to say probably not until after Valentine’s day. :frowning:

Random thought/question: could the white stuff be residue from silicone caulk or similar sealant? If so, then it would be firmly adhered to the tubing by now and is perhaps much ado about nothing, right? EDIT: I don’t think there are any large “chunks” that could clog things up if they detached from the tubing.

No white stuff is mostly likely mineral deposits due to the laser manufacturer using tap water during testing. We have seen videos of some of these Chinese places making tubes and it’s not pretty.

@Nedman Yikes. I wish I could say I was surprised. Any tips/gotchas on replacing the silicone tubing?