Barn is now built, called econoburn and asked what size line I should use?? They said 1" is all I need based on the fact that my unit will only produce 100,000 btu's. I bought some Vanguard PEX at Lowe's but I am rethinking that decision...I don't like how much it "grows" when heated and I am thinking that I need the O2 barrier. Has anyone used the Pex Al Pex for underground? I am planning on spray foaming the lines to the house (about 70 feet) and then to the pool (about 35 feet)