As I'm sure we're all painfully aware, distilled water is quite expensive and hard to come by here in the uk. So I don't want to waste any of it by cleaning my radiators and leak testing my system with it. Especially since it will just be going down the sink... *cough* ... I mean, being disposed of in a safe and environmentally friendly manner afterwards. So since it is just a small amount of time it will be in my loop and won't be subject to heat. Also it will be getting replaced with a premixed mayhems pastel fluid for the final build. Can I just use tap water?