So, I spent most of the day refreshing myself on Thermodynamics and Fluid Flow from my school days, to then do some ground loop calculations. I've done a couple whole-house load calcs, and I'm coming up with 22,000 to 26,000 BTUs heat loss for our county's 26F winter design temp. So, I've been sizing my ground loop for 3 tons to account for DHW that's not accounted for in the load calcs. With that my ground loop design: Soil type: Sand down to hardpan at 5 feet, where my loops will be. Soil Thermal Conductivity: 0.6 Btu/hr ft F (Annual rainfall = 70 in. almost all in the winter, and I'm putting infiltration trenches in-between the geo trenchs, so it could be greater than 1.0 at times) Loops: Four 800' loops of 3/4" HDPE, 8 pitch slinky in Four 100' long 3' wide trenches Design Ground Temp: 52F 20% propylene glycol mix Design Loop Flow: 3.2 gal/min Pump Flow: 12.8 gal/min Loop Head Loss: 24.8 ft Now, I need to find a pump. What's the typical head loss in the manifolds and heat pump? I don't want the pump to be undersized because I'm getting pretty close to laminar flow in the loops.