Hi, I'm new here but looked for years. I am stoked about using a, new to me dumont boiler in the shop. The boiler is piped with 1.5 inch black iron pipe to a 500 gallon propane storage tank. I still need to pipe to existing under floor pipe. The 130 dumont is replacing a memco boiler without storage that was underwhelming. My plan was to run it with 500 gallon storage and add on when I get some experience with the present setup. What I am having trouble with is chimney pipe. The manual says it is under a slight positive pressure with the dumont's induced fan. So I have checked Security chimney and Metal fab positive pressure chimney pipe. The prices for positive pressure pipe is two to three times the price of normal class A. So I wanted to ask if anyone can suggest a safe chimney pipe that is more wallet friendly than $280 per foot. I just need 10 feet through a simple roof and I thought maybe I am over building it. Thanks.