To anyone still watching this thread that could help me out. Is there any way to prevent ghost flow other than a zone valve? In my situation a check valve won't work because of direction of flow. Here's the situation. When my storage to FPHX circ is running, charging storage, it's pulling water through my garage heating loop because the way the storage headers are plumbed. Last year this wasn't a problem because I wasn't following nearly the amount of gpm I am now. With this new plumbing the flow rate is almost 3 times more. Here's some pictures for visual aid. Blue line - supply from storage to FPHX Red line - return from FPHX to storage Orange line - garage loop supply Green line - garage loop return So is there any other option than to put in a zone valve to block flow?