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.

Question:

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.