I am kicking around installing a geothermal system myself and I am planning to use an open loop system. Just in case that the open loop doesn't work out for some reason, I want to be prepared to install a horizontal loop. I have plenty of pasture land right behind my house to install the system so that will not be a problem. I also have a backhoe and a trencher so digging will also not be a problem. My 14 year old son loves to operate equipment so telling him to go out and dig some lines would be like telling most kids to go and play their playstations. So basically all I will have in this is the price of the pipe and pump system and a little fuel. Is there any real drawbacks to having more pipe that you actually need other than cost? I have read where they usually use HDPE pipe. I was just wondering why they don't the usual poly pipe like you use for underground water lines? Also I see where most people use around a 600 foot loop of pipe for 3/4 inch pipe for each ton And the loops are connected to an 1 1/4 manifold pipe underground before it goes to the house. If it is not very far from the house to the geo field, why couldn't you just run all the 3/4 lines into the house and connect to a manifold inside. This way, if one got a leak or something, you could just shut that one off until you got a new one installed. Also I see where a lot of these trenches are 6 feet deep going out and they return at 4 feet deep. I would think that you would want it the opposite. It would seem to me that you would want the water to be as warm as can be just before it returns to the house in the winter. And the warmest ground would be at 6 feet not 4 feet. I am not talking slinky loops here, just straight runs. Wouldn't it actually be better to run both lines at 6 feet deep ? My property is 500 feet wide and 1000 feet deep so I really don't care how much area it takes up. I just want it to be effecient.