HERMS coil stain

I am building an electric HERMs setup and water tested the seals on the fittings for the hot liquor tank last night (all weldless valves). It was late so I decided to let it go all night. When I drained the pot this morning, the stainless coil has like a dark stain on top of the tubing. Should I be worried about this or just clean it off an move on?

Try a little scrubbing to see ifn it’ll be removed ? Sneezles61

Clean it with. Muriatic acid paste. That what i use when done with. Stainless steel. Or aluminum welding. Than super cleaning. With sanatising. For food grade products. It will do the trick

Read Appendix B of “How to Brew” at: howtobrew.com

Thanks for the help. I’m going to take some bar keepers friend to it and see what happens.