Hi Jim,
I am a newcomer here but have been researching rocket mass heaters, mainly on line, for a little while.
Just getting geared up to build a water heater with ibc as thermal store. Your thread highlighted a couple of concerns I had, legionella being most important.
Does your system circulate from the heater directly through the ibc or does it work indirectly through a coil? If the latter, and assuming all other inputs and takeoffs are indirect, could the water in the ibc be treated with a chlorine bleach? I know that chlorine dioxide is used to kill legionella but I don't think there is a simple, cheap way of introduing it to the system.
Martin.
