Hi there. We purchased a house a few years ago that is an older home that had gone through several remodels over 90+ years (some good, some bad).
Anyway, I noticed the other day that the galvinized vent pipe from the water heater in the basement was severely rusted and corroded at the point that it enters a chimney to vent. The water heater itself is located about 8 feet from the chimney and the vent extends mostly horizontally (but properly pitched, I checked), then does a 90 degree turn, then runs into the chimney. Total run for the galvinized vent pipe is about 10 feet until it enters the chimney where it presuably goes out through the roof all the way from the basement. The chimney itself is no longer in use and I cannot find anyplace where a fireplace or anything was ever hooked up to it. There are no other appliances (e.g., furnace) hooked up to the same vent or to the fireplace. The rust and corrosion occurs only at the point of entry to the chimney and not any closer to the water heater itself.
I replaced the corroded pipe with a brand new one and everything looks ship-shape, but I just want to make sure I’m not missing anything. Should I be concerned that, for example, the chimney itself is not venting properly (clogged or something?) and call a chimney sweep or something? Is it likelier that maybe it was just a little rain pentration into the chimney itself and thus not a concern? I have no idea how old the pipe itself was. It was severly rusted and corroded (I could peel that part apart like paper), but the water heater itself was installed in 2013 with permits so I’m assuming that the vent pipe was at least not visibly corroded at that point (if not brand new).
Should I be concerned, or is this something more along the lines of “Watch it to see if it continues to rust and you might need to deal with chimney moisture or replacing the vent pipe every few years (it was fairly easy to replace, so I’d be fine replacing it every few years, but I don’t want to be in danger or something when it appears it is fine/not rusted).
Thanks!
Replies
If the corrosion appeared to spread out from the actual contact point between steel pipe and tile flue, likely the cause is electrolysis. This will be seen anywhere there's a connection between steel and masonry. You could possibly prevent it by inserting a layer of pseudo-asbestos fabric in the joint, to keep the two from touching, but the rate of the corrosion is probably so low that this step is unnecessary.
Could be if you live in a cold climate that the large flue is too big for the water heater. Years ago I had pretty much the same thing happen in an old house I owned. The flue gets cold in the winter, then warm moist exhaust from the water heater hits the cold flue, causing condensation, and can also make it not draw.
If that is the case, you might want to consider a power vent hot water heater, they can be vented with plastic, either horzontally, or vertically.