What water should be used in a water jacketed CO2 incubator? The manual says to use "sterile distilled water", and when asking VWR by telephone, or looking at ThermoFisher online, they say it should be 50K - 1 M Ohm, and pH 7-9. We have a MilliQ machine for ultrapure water, nevertheless we ordered Poland Spring distilled water since the ultrapure is 18 M Ohm. However, I looked up the specs, and the Poland water is pH5. Calling VWR they didn't resolve it. They want the given parameters, and he worries about the effect of adding something like sodium bicarbonate.

Is everyone else simply not worrying about this? What do you use?