I recently had an indirect-water tank added to my multizone gas-powered hydronic heating system. The supply line from the boiler to the water tank heats up considerably every time one of my heating zones is enabled, even when the circulator for the water heater is off. This seems wasteful. I also worry it will cause irregular (and perhaps dangerous) domestic hot-water temperatures, since heat is reaching the water tank in an uncontrolled manner.
Is there a simple piping fix (e.g. heat trap?) that will prevent boiler water from reaching the water tank unless its circulator pump is enabled?
Is this evidence of an installation/design error, or is this a common drawback of indirect water tanks?