Why the furnace flue in a Bradley bungalow was full of rust flakes

By Jacob Dove, Friendship Chimney Sweep

The symptom

A homeowner south of Broadway in Bradley called because the small cleanout door at the base of the chimney kept filling with reddish grit. The chimney had not vented a fireplace in decades; it served the gas furnace and water heater, the way most of Bradley’s old factory-town houses do. They were worried about a nest. It was not a nest.

What was happening

The furnace had been replaced about twenty years ago with a mid-efficiency model. Its exhaust is much cooler than the old furnace’s, so instead of rising hot and dry up the flue, it condenses on the cold clay tile in winter. The condensate is mildly acidic. Over twenty winters it dissolved the mortar between the tiles, and the mortar, plus flakes of the tile face, fell to the bottom. The camera showed joints that were open all the way around for the first ten feet, with tile pieces sitting on the cleanout ledge. Left alone, one of those tiles eventually drops across the flue and the furnace exhaust backs into the basement.

The fix

The flue got an AL29-4C stainless liner, the alloy made for condensing gas exhaust, sized for the combined input of the furnace and water heater with the connectors reworked so both vent properly. It went in from the top in a morning. The old tile stays in place around it, no longer doing any work. The homeowner now has a flue that will outlast the furnace, and no more grit in the cleanout.

If your Bradley house has a gas furnace venting into the original chimney and you have never had the flue scanned, this is the inspection to book before the heating season. It is quiet damage until the day it is not.

If this sounds like your house: we handle chimney relining for gas appliances across Kankakee County, and our Bradley page covers what we usually find there. Call (815) 449-4264, 7am to 9pm, any day.

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