I have a wood furnace in the basement. Water leaks threw the thimble when it is hot, not into the furnace, but at the thimble down the wall. The pipe connects into the wall under the garage slab and the cement block chimney is in the garage. There is no clean out door, just a bunch of rubble under the thimble. The wood is well seasoned oak. There is no surface water puddles outside the garage when it does rain, which has been redirected well away from the house for 3 years. The furnace has been used for about 8 years, and and started leaking last spring. I would estimate about 1 gallon of water in 12 hours. No plumbing near the garage either. Any thoughts? P.S. love these forums 
