I'm installing a new fuel oil water heater in a home we've just purchased. The unit calls for Type L, which has been difficult to source in my very rural area - and postage from mail order outlets is prohibitive, but may be necessary.
My understanding is that Type L is designed for continuous burn not to exceed 570F, and Double & Triple Wall Stove Pipe is designed for 1000F continuous burn.
Can I substitute Double Wall Stove Pipe for Type L?
In either case, I would be using a Tee with a Barometric Damper.
In an attempt to be ultraconservative, I've already tried to make-work Metalbest Class A Insulated Chimney Pipe, but limitations on fitting angles won't allow for flue connection from the unit.