Why does city water cause a pink ring at the water line in my toilet ?

The pink ring could be a mineral but also could be a airborne bacteria Serratia marcescens. Is it just in 1 toilet or do you also get it in sinks, the tub, drinking glasses? Here is a link with more information. Hopefully it is not a water quality issue and could just be old pipes.

https://www.ewswater.com/pink-stains-in-your-toilet-bowl-and-bathtub-heres-how-to-get-rid-of-it/

Ugh clean back of tank then add bleach to sit overnight. Ventilate! The in am flush and clean bowl. I believe u have a form of mold.

Good Morning Woodwardsb, What you are seeing is an airborne bacteria that likes damp places, and can live off practically nothing at all, but is particularly fond of feces, hair conditioner scum, soap scum, etc. (can be found in kitchens but usually in bathrooms due to ideal conditions). It can, AND DOES, cause illnesses such as urinary tract infections and respiratory problems, and infections in anyopen wounds (which is why it is always advisable to wear shower shoes IN the shower, and if sitting on tub edge or tub seat for any reason ALWAYS sit on a clean towel even if the water is running, and then wring the towel out, as this stuff is present BEFORE you see the pink). Below is information about it and what YOU can do to limit its presence and hopefully eliminate it all together. Good Luck, and thank you for using HOMETALK for solutions :)

https://www.ewswater.com/pink-stains-in-your-toilet-bowl-and-bathtub-heres-how-to-get-rid-of-it/

http://homeguides.sfgate.com/kill-pink-mold-shower-tile-89604.html

http://www.huffingtonpost.com/thrillist/5-gross-things-in-your-sh_b_8523284.html

https://www.brentwoodca.gov/civicax/filebank/blobdload.aspx?BlobID=23215

It's an airborne bacteria. I find that with any kind of ring in the toilet you need to throw several dental tabs in there and leave it for a day or night. Might have to do it a couple of times to start then you can keep it clean.

Think coke/alka seltzer/ diluted bleach overnight might clean it. I get this 2 & never knew what it was, usually just brush it away. Now I know, I'll prob start lowering lid when flushing.

I've also seen this red (and black) ring problem in toilet bowls where too much bleach is being used in the tank with cheaply made rubber flappers or balls. The bleach will dissolve the rubber and slime the tank and bowl. I replace the flapper and balls, drain and scrub the tank and start fresh.

I would be calling my local city council / water supplier if that was happening to me. However I would first see if it does it with a glass of water - if this does not happen then it is possible you have a build up of something in your toilet cistern. Perhaps you could try pouring in a bottle of vinegar at night and not flushing the toilet until morning and see if that makes a difference (I have no idea if that will work but vinegar is a wonder cleaner).