Boiler vent question

Clay lined masonry chimney used to vent both the water heater and boiler both NG. The w/h vent has a liner that extends to the top of the chimney. The boiler is a 12 year old 80+ efficiency that has no liner. Evidence of condensation rusting out galv at point where the vent enters the chimney. Is a liner required for the boiler?

Don’t go there.

Recommend alevel 2 chimney inspection by a qualified person.

As a research project I would acquaint yourself with the boiler mfg. recommendations for the flue.

Yes, it needs a liner or b-vent if it is vented in a masonry chimney.

I agree with the requirement of a pipe. If it was a old oil furnace that would be ok. The exhaust gases are not hot enough to warm the whole mass of cold air in the chimney and it’s causing your rusting issues. Plus if the seal between the pipe and the masonry isn’t good you could be getting spillage back into the structure.