I have a "blacklight" to check for dirt and noticed the water in the toilet bowl and a sinkful of water in the same bathroom had a distinct greenish color? I poured a lot of bleach into the toilet to clean in out and the water then looked colourless under the blacklight (with the bleach). After cleaning and flushing a couple of times, I was looking at that greenish water again under the blacklight. This is actually serious because I am quite ill and one of the bacterial infections I have has some ability to fluoresce. I tried to get some information but it was way over my head and I don't know where else to turn at this point.

I suppose my question would be: what is the normal color of water when it is exposed to a blacklight? Should it change at all and if it does, is there something to be concerned with? Your help will be much appreciated.

  • Is this a city or private water supply? Where are you located?
    – gregmac
    Jan 4, 2015 at 21:03

2 Answers 2


You should take a sample of the water to a lab for analysis if you're really concerned. There are minerals that fluoresce under UV light, so it could be that and not bacteria. But I doubt that anyone other than a lab will be able to offer more than speculation on the matter.

  • 1
    I agree. It's relatively inexpensive to have a basic water quality test done, including bacteria.
    – Hank
    Dec 30, 2014 at 3:29
  • Fluoride is a common mineral added to water that will fluoresce.
    – diceless
    Dec 30, 2014 at 17:45

The chlorine in the water will kill any bacteria. Lots of things fluoresce, most are harmless.

Get a water filter maybe.

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