Water turning plastic pink/brown - why?

Old 02-06-16, 10:44 AM
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Water turning plastic pink/brown - why?

I bought an old house about a year ago and noticed that my clear plastic items in my dishwasher, and plastic in my shower is getting stained pink/brown. Photos below. It doesn't scrub off of dishwasher items. It can be scrubbed off in the shower. Maybe associated with hot water, since it's shower and dishwasher? I have a tankless double boiler hot water system, about 35 years old. I have lived in this town for a while and I didn't notice this problem at other homes (city water supply doesn't seem to be an issue, but who knows...). What could be causing this, and how could I fix it?

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Old 02-06-16, 12:10 PM
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Welcome to the forums.

If it were just red stains I'd say iron but that pink residue is not usually a rust issue.
The pink stains are usually caused by the presence of pink biofilm. The pink is not hazardous. Any product containing bleach will remove it.

Biofilm is typically composed of many different microorganisms and bacteria held together by biological polymers that improve the ability of bacteria to adhere to and proliferate on wet surfaces. Most often found in shades of yellow or brown, biofilms can be many colors, including pink, orange, salmon, or coral. Because they thrive in the presence of water and the most minute trace of nutrients, biofilms are found virtually everywhere there is water.

You can read more here... page attachments//Pink_Stains.pdf
Old 02-06-16, 02:31 PM
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Have the water tested of you really want to know what it is.
Old 03-02-16, 05:35 PM
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The pink coating on the shower plastic scrubs right off. So I agree that is probably the pink biofilm. However the orange/pink discoloration on the dishwasher items like the plastic baby bottles and accessories does not scrub off. I've soaked it in strong bleach solution, and also tried a baking soda solution, soaking with each for a few hours. Neither did a thing. Could these be two separate problems? Or could it be the same problem that affects different types of plastic differently? I do plan to contact my city water department to inquire. Lastly, is there a way to fix it, like with a whole house filtration system?
Old 03-03-16, 06:04 AM
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The dishwasher heat may be causing a chemical bond to take place causing the plastic to stain permanently. You can try an experiment. Take one of those clear bottles and put it into a larger bottle full of water. Then put that into dishwasher. When it's done is the immersed plastic bottle still clear?

PJ...What made you come up with the biofilm idea. Very clever and very good. I would never have thought of it.

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