Foamy drinking water on city water - solved

I know this has already been discussed but the conclusion there seems to be that antifreeze got left in a corner of a line somewhere. That isn't the case as our RV hasn't been winterized for several years.

The water was really fizzy running on city water but not from the fresh tanks. Water sitting in a glass was cloudy with bubbles for several minutes.

Long story short, we replaced the white drinking water hose and the problem went away. Somehow it must be breaking down and contaminating the water.

I saw several people comment that there might be a leak that's letting air in. I don't get that - if there was a leak, water would come out not air in???