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A Kensington homeowner reached out to Tim Whistler Plumbing about an unlined masonry chimney that was venting both their water heater and furnace. Under current building code (the May 2015 update requires all masonry chimneys used for exhaust to be lined), the setup needed to be brought up to current standards to safely vent the combustion gases from both appliances. We did a virtual estimate the same day they called, and our crew was on site the next morning to install the liner.
An unlined masonry chimney venting gas appliances is a real carbon monoxide risk. Over time, condensation from combustion gases can break down the mortar inside an unlined chimney, opening gaps that let CO seep back into the living space instead of safely venting out the top. The homeowner's furnace exhaust flue also showed signs of corrosion and needed to be replaced as part of the same job. And because both the water heater and the furnace shared the chimney, the new liner had to be sized to handle the combined exhaust load, with a properly built tee connection joining the two flues into the liner.
Two technicians completed the entire job in less than a day. We installed a properly sized metal chimney liner down through the existing masonry chimney, replaced the corroded furnace exhaust flue, and built a tee connection so both the water heater and furnace could safely exhaust into the new liner. All penetrations were sealed with high-temperature cement, the cap was folded and sealed with high-temp silicone to prevent water infiltration, and every connection was tested before we left.
An unlined masonry chimney that's still venting gas appliances is one of the most common code violations we find in older DMV homes, and it's one of the easier ones to fix. A properly installed liner cuts the carbon monoxide risk dramatically and brings the home into compliance with current code.
The homeowner now has a code-compliant, properly lined chimney safely venting both their water heater and furnace, with a new flue connection that's built to last. The whole job took less than a day, with no disruption to the home's heat or hot water. The cost was modest compared to a full venting overhaul because the existing masonry chimney was structurally sound and just needed to be brought up to current code.
If you have a water heater or furnace venting into an unlined masonry chimney, get it checked. Carbon monoxide is invisible and odorless, and the fix is usually a one-day job. Call Tim Whistler Plumbing at 1-866-477-6190 for a quote on chimney liner installation across Kensington, Silver Spring, Bethesda, Washington DC, and the rest of the DMV.
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