Rusty Water Heater Vent Pipe in New House
We've been in our new home just 4 months. We have a 90% efficient gas water heater in our basement which is vented through the attic. The pipe has two curves between the basement ceiling and the top of the water heater. Both curves have quite a lot of rust on them plus there is rust on the top of the water heater. We're wondering if the problem is that the pipe sticking out of the roof is too short. The plumber said our rust problem is the worst he's seen. He told us that the vent pipe should be above the roof peak, but it's several feet below it. Is the rust likely from the short pipe or could there be another reason?