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Why Is My Furnace Leaking Water?

February is ending with a few warm weather surprises here in Chicagoland. Some days have even gotten up into the 60s! But we can’t let this deceive us into believing that it’s already time to shut down our furnaces for the season: March is infamous for the way it can throw harsh cold snaps at us, and even April can turn chilly. Your gas furnace isn’t done with its workload yet—and it’s more important than ever to act fast and call for furnace repairs if you should notice any furnace behavior that doesn’t look right.

And water leaking from the bottom of your furnace? Yeah, that definitely doesn’t look right!


My furnace isn’t a boiler—why would it leak water?

This is the whole reason that water leaking from the bottom of a furnace is such a strange sight. Gas furnaces do not use water to provide heat to a home the way a boiler does; they operate through igniting natural gas burners to create hot combustion gas, which then enters a heat exchanger where it transfers thermal energy through the heat exchanger walls to the air from the blower fan.

However, it’s the heat exchanger that is often the source for water leaks, especially if the furnace is a high-efficiency condensing furnace. These are among the most energy-efficient furnaces on the market, able to score an AFUE rating of up to 98.5%. These furnaces contain two heat exchangers; the second heat exchanger condenses the exhaust vapor from the first, and this process creates water condensation. This is removed from the furnace through a floor drain. Like any drain, it can become clogged, and when this occurs, the tubing that leads to it will start to leak. There could also be leaks along the tubing that leads to the drain.

Another possibility is damage to the second heat exchanger that is allowing the condensation to escape and leak around the unit. This usually means the entire heat exchanger must be replaced. For an older furnace, a full replacement is often the most cost-effective solution.

But what about non-condensing furnaces? The source of the water might be blockage inside the flue that allows exhaust vapor from the heat exchanger to escape. The exhaust vapor will start to condense inside the flue pipe, then leak back down as water. If you have a whole-house humidifier installed, it might be the problem, not the furnace. This still requires repairs, however, since the water can trigger corrosion in the furnace, which is bad news!

Call HVAC Professionals without Delay

No matter what the ultimate source of the problem is, when you spot water around your gas furnace, call for furnace repairs in Park Ridge, IL or elsewhere in Chicagoland from our team. Gas furnace work must be left to professionals. It is risky for an amateur to tamper with any appliance connected to a gas line. Stay safe and get your family warm again by relying on our expertise and experience.

Brilliant Home Services: Servicing Chicagoland since 1956. We have 24-hour emergency service for your convenience and comfort.

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