Stumbled across a 40 litre urn that I was hopping to use to double batch biab but it has some thick "limescale" looking build up on the base and starting to go up the sides. It flakes of in some areas but is pretty firmly stuck. I've given descaler from the supermarket a crack but it would send me broke diluting to correct ratio so that's out. From a search I've read about using pbw if you have it but also vinegar and citric acid. Does anyone have a sure fire method with quantities/dilution I can use. Cheers [emoji481][emoji481]