How often should you change CO₂ laser coolant, and what goes in it?
The water cooling your CO2 laser tube sits warm, in the dark, under laser light, all day. That’s a greenhouse. Change the CO2 laser coolant every month or two with distilled water, and if the shop can freeze, mix in propylene glycol, never past 50/50.
Applies to
- Process
- Water-cooled CO₂ laser tubes (pump-and-reservoir or chiller)
- Water
- Distilled only
- Antifreeze
- Propylene glycol, 20–50%, never over 50/50
Why it matters
Warm water plus light is exactly what algae wants. Steve Makes Everything changes his every month or two so nothing grows in the tube’s water jacket.
Cold shops add a second risk. Water that freezes inside a glass tube can crack it, so in winter he mixes in propylene glycol. It’s the low-hazard antifreeze that’s even used in food production.
Then the bubbles. Air trapped in the tube leaves part of it uncooled. Always run the pump after a refill and look.
What good looks like
- Clear coolant, no green or cloudy tint
- Tube water jacket full, with no air bubbles
- Glycol share right for how cold your shop gets, and no more than 50%
How to apply it
- Unplug the laser and the pump.
- Pull the return line (water coming back from the tube) and put it in a bucket.
- Plug the pump in and let it push the old water out. It doesn’t need to be perfect. Don’t let the pump run dry for long.
- Unplug, reconnect the line, and empty the reservoir.
- Add propylene glycol if you need it, 20–50% of the total, then fill the rest with distilled water.
- Run the pump, top up, and run it a while longer. Check the tube for air bubbles before you fire the laser.
Exceptions & tradeoffs
Warm shop that never freezes? Plain distilled water is fine. Steve’s shop rarely gets cold, so he runs less glycol than the max.
If your tube or chiller maker specifies a coolant, use theirs. Their warranty is reading the manual, not this page.
Common mistakes
- Topping up with tap waterDistilled only; tap water carries minerals and grows algae faster
- Going stronger than 50/50 “for extra protection”Cap propylene glycol at 50% of the mix
- Grabbing car antifreeze off the garage shelfPlain propylene glycol, unless the tube maker says otherwise
- Firing the laser straight after a refillRun the pump first and clear every air bubble
Frequently asked questions
- How often should I change the water in my CO₂ laser?Every month or two. Warm water under laser light grows algae, so Steve Makes Everything replaces his on that schedule.
- Can I use tap water in a laser chiller?Use distilled water. Tap water brings minerals into the cooling loop.
- What antifreeze is safe for a CO₂ laser tube?Propylene glycol, mixed at 20–50% with distilled water and never over 50/50. Use less if your shop only gets cool, not cold.
- Why are there bubbles in my laser tube?Air gets in when the loop is drained and refilled. Run the pump until they clear, and don’t fire the laser while any remain.
Unplugging, pulling the return line and pumping the old water out — Laser Machine Maintenance ↗ at 10:36.
Replace the water every month or two; warm water and laser light grow algae — Laser Machine Maintenance ↗ at 11:29.
Propylene glycol at 20–50%, never over 50/50 — Laser Machine Maintenance ↗ at 12:38.
Distilled water only; run the pump and check for air bubbles — Laser Machine Maintenance ↗ at 13:13.
The schedule, the drain method and the glycol range are Steve’s. The car-antifreeze warning is ours. It’s the mistake I’d have made.