What are the dangers of brewing beer in a plastic watercooler labelled with a 7 mark?
The “7” (other) plastic is probably safe if it was used for water. There is some leaching of plastic into the wort but, for a stay of a week or two, this is minimal. The problem comes with the ridges (if present) in the jugs. Cleaning them would be next to impossible. What you can do is use the jugs for short-term storage of boiled water. If you have enough of them, they would make a hell of a trombe wall. That won’t help your brewing, though.
