So now that the heating load is off (or mostly off), and I've been burning for a little while just to heat DHW most of the time, I've noticed something about my setup that I didn't notice in heating season. When the boiler is out & gone cold, and I get a call for heat that sends hot water to a zone (right now my sidearm), I'm pulling some water through my boiler. I think most is coming from storage, but it is enough to put most of the now-cold boiler water through my sidearm & partly into storage. So I'm losing heat. I checked out the diagrams in the 'simple storage' sticky, and I can't figure out what would stop the same thing from happening there too - although I'm not sure what the little square doohickey is in the top of the wood boiler supply piping. I could stop this by closing the ball valve in my boiler supply pipe after the boiler has cooled off but I'm not fussy about that in the event I forget to open it some time I'm building a fire in a hurry - although my dump circuit would still be active. I thought the LK810 would prevent some of this, but it goes right through it - which kind of makes sense too though as it is also supposed to allow convection flow in power outages. So for starters, why wouldn't this happen in the 'simple storage' sticky scenario?