Old unused flue

[BigJ273]

I posted before about this but didn’t get much response. Seeking advise from anyone who’s had previous experience w this

Back in November we replaced an oil boiler with a condensing boiler, no longer needing to use the chimney flue. The flue was sealed at the bottom and the condensing boiler hung on the wall over the opening, making it no longer accessible. The flue has a rain cap on top, allowing for ventilation at the top.

There’s no visible evidence of anything so far, but is there a real risk of moisture buildup in the flue or am I worrying for nothing? It is vented at the top through the rain cap. My major concern, and where I’m kicking myself in the butt, is allowing the boiler to be hung over the bottom flue hole that was sealed. Now it’s no longer accessible from the bottom end, which is a little unsettling.

 

[begreen]

Is there a cleanout below the blocked-off flue hole?

 

[BigJ273]

Is there a cleanout below the blocked-off flue hole?

There is not. The blocked off hole is a short horizontal clay tile thimble that connects to a vertical clay tile that runs to the top. Nothing below it. It’s a 90 degree angle

 

[begreen]

Is it an interior or exterior chimney? If it is an interior chimney, just cap off the top.

 

[BigJ273]

Is it an interior or exterior chimney? If it is an interior chimney, just cap off the top.

Its exterior. The door u see on the bottom right is an ash Cleanout for the other fireplace flue.

 

[BigJ273]

The yellow line shows the path of the old boiler flu

 

[BigJ273]

I was wondering if I could have some type of Cleanout/inspection door installed on the outside. But I don’t know how that would work with the clay tiles

 

[BigJ273]

Any opinions? Didn’t get many responses

 

[begreen]

It's most likely not necessary, but could a new hole could be made below the boiler or on the other side of the chimney in the basement?

 

[EatenByLimestone]

I probably have a different perspective than most as if I have to work on a chimney, it’s probably been neglected a long time. Bats, raccoons, wasps, or squirrels have taken up residence.

That said, I see lots of bad crowns and pointing that have been letting water pour into voids for years. By the size of some of the bat colonies, 50+ years. Most of these chimneys do not have weep holes or drains on the bottom. They are still structurally sound. The water must be seeping out pores in the brick and mortar. If you capped the top and the bottom is sealed, condensation will leave the same way.

 

[begreen]

*> There’s no visible evidence of anything so far, but is there a real risk of moisture buildup in the flue or am I worrying for nothing?

The boiler take-off is to the side according to the diagram. If there is going to be an issue, I would expect it to show up in the main chimney.

 

[BigJ273]

It's most likely not necessary, but could a new hole could be made below the boiler or on the other side of the chimney in the basement?

No basement. And the crock from the old boiler runs 90 degrees horizontal, then goes straight up, like the yellow line shows. The only solution I can think of if we ever needed to access it (besides taking the boiler down), would be to bust a hole in the outside brick. Of course, that would be a crap show. So far it’s been good, but we also haven’t hit the humid season.

 

[BigJ273]

The boiler take-off is to the side according to the diagram. If there is going to be an issue, I would expect it to show up in the main chimney.

I’ve never noticed any issues in the main chimney. It’s lined now with ss for the wood stove. But for 30 years it was just a clay liner and the chimney was never used. So I would agree w u, if it was gonna be an issue it would have also been an issue there. Never thought of that