Water heater riser pipes

[Joshua L. Frederick]

I know that the riser pipes at the top of a water heater should be rigid/sem-rigid (min. 18" I believe?), especially on a gas water heater near the draft hood. Anyway, can anyone show me any documentation/wording/pictures etc. to support this? I'm having trouble finding any information.

Thanks in advance.

[Jeffrey R. Pope]

Probably because there is no such requirement. . .

[mnahrgang]

They just have to be installed according to manufacturers instructions. If you google the make and model you might be able to find a digital copy of them, and confirm that your instance is according to those...