Resmed AirSense 10, humidifier discoloring on bottom?

[Melman]

I am a microbiologist and worked for years with high purity pharmaceutical water systems that produce water of a much higher purity then what we buy at the supermarket. Microbial growth is a significant problem in such systems if they are not properly controlled because distilled water is not just H2O. It contains some organic carbon, often lot's of inorganic carbon in the form of CO2, and many trace minerals and ions. There are numerous species of bacteria that grow well with only trace amounts of organic nutrients and species that need no organic nutrients. So there are bacteria that will grow in distilled water.

That being said, they are not a threat if reasonable hygiene practices are followed. I seldom clean my humidifier  with detergent.  I don't even empty it completely daily. I top it off daily with distilled water and completely drain it every couple of weeks. I have seen no indication of microbial growth. If I let it set undisturbed for a month or two, however, I'm sure I'm sure a slimy layer of microbial growth would occur.

Sorry for the lecture but I don't like to see incorrect information (and I know it's well intentioned) in the forum. Also, bacteria don't explode in warm water. They are sturdy little devils.

[SarcasticDave94]

FWIW my ResMed AirCurve 10 ASV with 59.7 hours on it has 2 spots of slight discoloration on the metal bottom of the humidifier tank. Note that I run my humidifier only on manual and the lowest setting I've tried is 4. It's never ran out of water. Do I think it's a big issue? No. Just saying this discoloration happens. Oh and I've only used distilled water.

[toadisland]

how much water is used from the humidifier is strongly dependent on the ambient humidity

[SarcasticDave94]

I agree in nightly usage varies per user and even per night as I've seen. Again I'm using mine in manual mode. I did try auto mode the 1st night but it was not enough humidity for me. And FWIW I have to run a window A/C overnight every night to keep the bedroom at 68° F. This bedroom is finicky in temps besides. Of course YMMV
Dave B.

PS so far on setting of 7 with heated hose on 85°, I've used half a tank or just under per night.