Water in Chimney cleanout - can I seal it with concrete and close off the cleanout?

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tom w

Member
Feb 22, 2015
19
upstate ny
I have an older brick chimney that my oil furnace vents to. The previous owner had also had a woodstove connected to the same chimney, but years ago I had that changed to a steel double wall stovepipe for the woodstove. So the chimney is jsut for the oil furnace, and the furnace venting enters the chimney about 12" above the cleanout.

Just recently, for the first time in the 28 years I've lived here, I got water dripping out of the cleanout door at the bottom of the chimney. I had about 2" of water there, in a depression in the middle of the cleanout. Vacumed the water out a week ago, kept an eye on it. We've had about an inch of snow which melted since then, and now I have even more water. than before. No way this is condensation. And I think I now see the problem... 2 years ago I had a contractor install a french drain that runs flush with the outside wall of the chimney. At the end of the cleanout, it's open...there's just a little dirt and I can actually see the plastic of the french drain! I'm contacting the contractor, because they should have seen there was a hole in the back of the cleanout, or maybe they made the hole accidentally. But before I do, I'd like some ideas on the best way to fix it.

The opening at the end of the cleanout up to the chimney is small, only about 3-4" deep x the width of the cleanout which is about 10". So my questions are:
-Do I really need the cleanout... can I just seal it off?
-If I don't need it, what's the best way to fix this?
-My thought is to seal that open wall of the cleanout with hydrophobic concrete, from the inside of the trap (ground is forzen, no way I'm digging down there now). And in doing so I'll probably seal the upper opening to the chimney flue, it's unavoidable given how little depth that opening has.
-Is there a better way?
Thanks for any ideas!
 
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