That's what I am doing MNBobcat. My water on the the Boiler side is already softened so I do't need it there for that. Your needs might be different. I am going to put a strainer of some sort on the flat plate's boiler input side to keep any crud from getting through and clogging the plates. If I cheap out, a wye strainer, if not a Jomar filter valve like the one I just got to put after my storage tank's outlet to catch wayward crud from it's previous life from getting into the system. Those two Webstone valves just arrived a week or two ago from PexSupply.
Mike
Mike