I'm posting this for a co-worker of mine who has a problem with his chimney. Whenever we get a real cold snap - like now - water drips from the ashbox. I'm thinking frozen water from previous snow and rain is getting thawed by flue gases. Although we haven't gotten much of either lately. Perhaps it's moisture from the combustion process, itself. Here's what I know so far...

- The furnace is an old hot-water boiler.

- The passive-draft burner was replaced three months ago.

- There are THREE 90° elbows from the furnace to the chimney flue.

- A Magic Heat is in place between the second and third elbow.

- There is no barometric damper, or a tee to accept one.

- It's possible that the nozzle is different from stock.

- There is no water leakage beneath, or around, the furnace.

I'm worried his chimney liner will be destroyed by constant freeze-and-thaw cycles. Is this a legitimate fear?

I'm guessing that the stack temp is too low. So not all of the moisture evaporates; It freezes, instead. This could be from a combination of the Magic Heat, an undersized nozzle, and draft leakage from old flue pipes (one is sagging). It could only one or two of these factors. I don't know.

I've not actually seen the setup - just relaying what my co-worker has seen. I know this is not much to go on. With more info I may know what to look for when I see it. Would measuring the stack temp be a good place to start?

At the least, he could use a chimney cap. That should prevent most moisture from the outside, anyway.

Please let me know what you think.

Marco