Domestic Hot Water Header Tank For FV or Mash Tun

[alan.monaghan]

Is there any reason why a plastic header tank for a household hot water cylinder would not be suitable for a fermenter, or even a mash tun? I assume they're food grade, although as they are not usually used for drinking water I may be wrong. I'm guessing that the lids can provide an adequate seal to allow an airlock to be fitted for fermenting Also I'm not sure whether they will withstand mashing temperatures, although they must allow for heat transferred from a hot water cylinder. Has anyone used one?