I had the same problem shortly after I moved in to my current
apartment. I knew someone who, in her own words.. "makes the
water for the town". I guess it's a treatment facility. At any
rate, she'd never heard of it. She asked her supervisor and neither
had he. Within a week, in their professional pulication, was an
article about pink stain. It was somewhat vague, but what I gathered
was that it was a bacteria that grew in hot water only. Similar to
mold, you just keep it clean. However, the root cause could be in my
hot water heater. My concern is... how safe is it. It reccomends not
drinking the hot water. I stick my face in the "bacteria"
hot water every morning in the shower, as does the rest of my family.
If their was mold coming out, I certainly wouldn't be bathing in
it!!! If it is of concern, I should think the landlord shoud replace
my hot water heater. Although it could be in the pipes, as well!!
Sorry, I am not of much help!! Good Luck