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by ridgeguy 2778 days ago
CPAP with humidifier user here. About nondistilled water:

My humidifier has a heated metal plate in the bottom of the tank. Its temperature is set on a humidifier scale of 1-8, plate temperature increases from 1-8.

Evaporation of nondistilled water will leave mineral deposits behind. Deposits decrease thermal conductance between heated plate and water. This will reduce evaporation rate, reducing effective humidity for a given setting.

If the control loop is smarter than usual and includes humidity sensing, there's a potential for thermal runaway. Doubt this is an issue, it's probably a simple temperature loop. I don't think you'd "fry the entire machine in days".

There may be more bacterial growth potential with nondistilled water. Don't know.

Using distilled water is a little less convenient, but could avoid some issues.

2 comments

It's really not a big deal to use tap water, I did for years until I lost enough weight that my sleep apnea went away.

1.) Fill the tank with regular cheap vinegar to get rid of the mineral deposits. Maybe there is a problem with some tanks, but mine were all plastic or stainless steel and vinegar didn't seem to have any affect on them.

2.) Usually the tanks hold enough water for two nights, maybe a little more, at the settings I used them at. Dumping out the water in the morning kept the mineral content from becoming concentrated due to evaporation, and kept the buildup down to more manageable levels. If I didn't dump the tank every morining then I have rapid mineral buildup. I know it sounds silly, but it took me an embarasing amout of time to figure this out.

Once I worked out those two things I had no trouble with using regular tap water in the humidifier.

> Evaporation of nondistilled water will leave mineral deposits behind

This is true, but it will take weeks or months, depending on your water quality, and is easily cleaned if you know how.

Days in seattle
OK. I realize tap water composition vary.

I normally use distilled water, but if I'm traveling and don't have it handy, I'm not losing sleep over using tap water 1-2 nights.