I just want to review what I have found online about head pressure. Since my EKO 40 will put out about 100,000 btu I think I will need to move about 10gpm. Assuming 10 gpm i belive 1" pex is about 6.1ft of head per 100' of pipe. Since I have 300' round trip I would have about 18.3ft of head in my pex alone. Add say 1 for the boiler and maybe 2 for the extra fittings and storage tank for a total of 22.3ft head. Acording to my taco 011 pump curve chart. 22ft of head is 10gmp. Are my assumptions correct in that I could get by with the 1" thermopex? I don't want my boiler going to idle because my lines won't move enough heat. 1 1/4 thermopex is not available in my area. Foam in trench is still being considered but I am concerned about the foam underground say 15-20 years from now.