I'd like to get feedback on my proposed Garn hydronic design from all the experts out there! I tried to simplify the design by keeping it unpressurized. I plan to heat 2 houses, a 25,000 gal salt pool, and a 500 gal hot tub. My focus at this time is on the larger of the 2 houses. The smaller home can be delayed until next year. We are completing the construction of a carriage house which houses a Garn 2000 and its location was strategically chosen because it is between the 2 houses and on one of the highest locations on the farm which is 3' above the bottom floor of both houses. While I want to make it simple, I am open to suggestions about how to make it better even if I have to scrap the entire design. Fortunately, I have my wife's support and I'd like to keep it that way by getting it right on the first attempt . I was hoping to draw from all the wisdom from those who post on this site so I can hopefully provide insight for others who might make the plunge and become more self-sufficient. I guess the biggest unknown for me at this time is whether a solenoid would be sufficient to keep water elevated at the highest point in the system which happens to be where a 17x20 and 20x20 supply plenum need water coils for the updraft propane furnaces. The bottom floor has 10' ceilings and the second floor has 9' ceilings. All 3 DHW tanks and a 14x20 propane furnace are in the attic at the level of the 2nd floor which is the level where any pumps and manifolds would be installed. However, the 17x20 and 20x20 propane furnaces are above the ceiling of the 2nd floor which is 16' above the level of the Garn's slab. So, this means that there is an additional 5' to raise water to those 2 supply plenums. This puts me 5' above the maximum 16' rise mentioned in the Garn design manual. I was hoping that zoning with circulators might offset this additional 5'. Could this work or should I just incorporate a FPHX and pressurize?