On Thursday, December 18, 2014 12:52:22 PM UTC-6, wrote:
I'm using RO water in an ultrasonic humidifier to rid the vapor of that white mineral dust, and it works well. However, while cleaning the humidifier I found a pink residue inside. The net says that this is bacterial in nature but I thought I'd check with you guys and assure myself that it isn't something the RO system is leaking into the water.

This is the system:
http://www.uswatersystems.com/system...apro-5050.html

This is the article:
http://www.wrintl.com/faqs.asp#Can_p...icro-organisms



Thanks.

If it was from the RO system the water would be pink before putting into the humidifier, so my bet is on a bio-slime caused by air-borne bacteria. The solution is to periodically clean the reservoir with a bleach solution.