I'd normally go directly to my geo contractor about this, but figured I'd post it here in case someone else had the same question. I just got my geo w2w system running. Previously, I was running a boiler system which had a taco radiant mixing block(rmb) located right before my zones. My rmb was used for a few things. 1) outdoor reset 2) prevented my boiler from condensation 3) mixed my exiting water temp from my zones with the boiler water to mix at a designed water temp. Example: boiler temp =150 deg, exiting zone temp= 100, desired mixing temp =120. I noticed last night that when trying to send 100 deg into the loop, when my exiting zone water was mixed with the buffer tank temp (100 deg), my entering loop temp would be reduced to 91-95 deg. My concern is now that I'm no longer mixing with such a high water temp, unless I increase my buffer tank temp, I'll never send the desired temp into my loops. My solution ,if needed would be to remove my rmb and install a circulating pump. Now my real question is whether it's more efficient to use 1 circulating pump for all zones, or is it better to have a smaller circ pump for each zone? Keep in mind my geo is still bringing the house up to temp, so I still have to see how the rmb performs once I'm at desired temp.