60,000 btu gas fired water heater installed by others 4-5 years ago.
3" b-vent dovetails into 4" single wall right at the ceiling line.
the 4" was capped off after it penetrated the roof. total length of
venting is 8 feet
eventually the 4" single wall corroded to the point it split open,
which then dumped the product of combustion into the attic area.
could the non-vented water heater cause water hammer?