I am looking for some input on the placement of flow check valves on an indirect water heater when used on a boiler system with zone valves.
I was on a service call the other day and the indirect water heater was returning water to the boiler return and also sending heated water to the heating loops because the zone valves were open on a call for heat. The circulator was on the return. There was a check valve on the feed to the indirect water heater. I was thinking that the one inch return should also have a check valve to prevent water flow to the heating loops, is this really needed and what would be the recommended type of valve. Is this overkill?
I have seen many indirect heaters with no check valves at all. Thanks.