Humm. Thank you for your reply. We plan on burrying the pipe about 24 inches because freezing is a problem. However we will also plumb a fitting to drain the system. The owner of the ranch, bless her heart, wants water in the cabin even in the winter, so we plan on burrying the supply system and then adding drain taps to the shower and sink.
The owner of the ranch suggested 1.5 inch pipe but I said, guessing, that would be "over-kill." However, it also occured to me that bigger is always better. :-) If they can afford the 1.5 inch pipe, I'll install it. I think polyethylene will be used since that is what is used on other parts of the ranch (there is water already going to The Big House and also water going down here in the bunk house where I live).
Your system uses a pump; the cabin where the ranch owners want water does not have any electricity (nearest power line is 22 miles away) so it must all be gravity fed. Elizabeth wants hot water, however, so an on-demand propane heater will probably be used. Since there will be no tanks at the cabin, perhaps we will skip the pressure relief valve.
Thank you for your reply.