I've had a stand alone type of whole house humidifier for many years. It has two 2.75 gallon white plastic water bottles. In addition to using an anti-bacterial with each fill-up, at the end of each winter I put some water in each bottle, add a little bleach and shake it several times. Then I rinse the bottles out, get as much water out as I can through the small openings and let them sit open for 1-2 weeks to thoroughly dry. Finally, I put the caps back on and store the unit away.

Yesterday, when I took it out to set up, both water bottles have large areas of brown discoloration inside as shown in the photo. I don't think it's mold. Could it be deterioration of the plastic? I'll be getting new bottles anyhow, but would like to know what happened to prevent a recurence.

Water Bottles

  • Why are you concerned about this? Don't you just normally dump the condensate down a drain? Commented Dec 19, 2020 at 14:59
  • 3
    @GeorgeAnderson If it's a humidifier, it's adding moisture to the air so these bottles are used to supply water, not collect condensate.
    – JACK
    Commented Dec 19, 2020 at 15:46
  • I almost asked the same question as George good catch @jack. A good sanitizer is hydrogen peroxide I would use a stronger solution maybe 8-10 % and rinse out.the great thing about hydrogen peroxide is if you don’t get it totally rinsed it breaks down into water and oxygen.
    – Ed Beal
    Commented Dec 19, 2020 at 15:49
  • LOL! Oops! good catch both of you! Here in western Washington State we don't generally have to worry about humidifying the air, it's plenty humid already. Thanks for the comment and correcting me! Take care and stay safe! Commented Dec 19, 2020 at 18:01
  • @GeorgeAnderson Growing up in Chicago we had the dehumidifier on in the summer and the humidifier on in the winter because of the furnace being on..
    – JACK
    Commented Dec 19, 2020 at 18:07

2 Answers 2


I called the manufacturer today and it was their opinion that the plastic had deteriorated.

  • Thanks for posting your answer; if it's the best one, you can accept it by clicking the checkmark. Commented Dec 21, 2020 at 16:42

That looks like iron staining to me. See also almost any commercial building with lawn sprinklers against the wall.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.