Would a flow check valve here (see red arrow) prevent thermosiphoning through my mixers

ThatF_inGuyInNY

And would it allow me to avoid using check valves on two mixers?

EdTheHeaterMan

I believe so.

Are you posting an "As Built" existing system, or are you still designing and want to cover all the bases?

Just want to know if we are solving a problem or if this is a hypothetical

ThatF_inGuyInNY

EdTheHeaterMan said:

I believe so.

Are you posting an "As Built" existing system, or are you still designing and want to cover all the bases?

Just want to know if we are solving a problem or if this is a hypothetical

All hypothetical. Im designing and want to cover my bases. I'm honestly not sure how important it is in general (i.e. how much heat I would actually lose in standby with this setup). But Im looking at one giant radiator on this wall and thinking a single $75 flowcheck would probably pay for itself eventually.

NOTE: I am planning to use pumps with IFCs.

hot_rod

No need for a check.I. The circulators will have checks. That covers the supply side. Those mixers have enough flow resistance inside that you will not get any unwanted gravity flow.

You technically don’t want checks on the inlet/ suction side of circulators anyways.

Also the hydroseperator provides a hydraulic disconnect between the boiler side and the distribution. As well as top to bottom flow within the sep, when no circs are running. So no gravity or ghost flow up the return side piping