Noticing water dripping out of your furnace or pooling up around the unit can be quite disconcerting. If you ever find yourself in this situation, surely the first thing you’ll want to know is why it is happening and how to stop it. Water leaking out of a furnace typically indicates that there is some issue with the unit’s condensate drain system, but it can also be a sign of a much more serious problem. Let’s now look more closely at these various issues and also how you can tell what is causing your furnace to leak.

Determining What Type of Furnace You Have

To determine why your furnace is leaking, you first need to know what type of furnace you have. The two main types of units are conventional and high-efficiency condensing furnaces. If you’re unsure of what type of furnace you have, the easiest way to find out is to look at its label to see what its AFUE rating is. If the AFUE is 90 or higher, then it is a condensing furnace, while an AFUE of 89 or lower means you have a conventional furnace.

You can also determine what type of furnace you have by visually inspecting the unit to see if it has a condensate drain system. With a condensing furnace, you will see a white or black PVC pipe coming out near the bottom of the unit. This pipe typically runs from the furnace to a nearby floor drain, but it may also run directly outside of the building if your furnace is on the main floor or in the attic.

Another simple way to tell what type of furnace you have is its age. All furnaces installed in Canada from 2019 onward are required to be at least 95 AFUE. The previous minimum was 90 AFUE, and this was set back in 2009. This means that the only homes in Canada with conventional furnaces are those where the furnace was installed prior to 2009.

Conventional vs. Condensing Furnaces

Condensing furnaces are sometimes prone to leaks as these units cool down the combustion fumes they produce to the point where any moisture condenses into water. As a result, condensing furnaces need a condensate drain system to handle this water and transport it away from the unit.

Conventional furnaces are less efficient and can’t capture as much heat from combustion fumes. This means that the fumes exit out through the exhaust flue before they can ever cool down to the point where condensation forms. As a result, conventional furnaces seldom show signs of a leak. If you do have a conventional furnace that is leaking, you should immediately shut off your heating system until you can have a certified technician inspect it.

The reason is that any water on or around your conventional furnace indicates that the exhaust system isn’t working correctly, and the carbon monoxide and other fumes aren’t being vented outside of the building. This typically happens because the exhaust flue is blocked or damaged. If the furnace isn’t vented properly, it means that the carbon monoxide will be trapped and start seeping back out into your home. This is obviously something you will want to have fixed immediately due to the huge potential for carbon monoxide poisoning.

What Causes a Condensing Furnace to Leak?

Condensing furnaces can leak for several different reasons, all of which are related to the unit’s condensate drain system. When water condenses inside the furnace, it first drips down into the condensate drain pan. A pipe is connected to the bottom of the drain pan that then carries the water away from the furnace and into your sewage system or out of the building.

The most common reason that condensing furnaces will start leaking is due to a clog somewhere in the condensate line. The combination of moisture and heat from the furnace often leads to mold and algae beginning to grow inside the condensate line and start clogging the pipe. Even if the pipe is only partially clogged, sometimes the volume of water will be more than the system can handle, causing water to start overflowing out of the drain pan. Contact us, and we’ll clear the line for you.

Another reason that condensing furnaces can leak is that the drain pan itself is damaged or corroded. Drain pans are typically made from plastic or metal, and either type of pan has the potential to leak. If the damage is fairly minor, the drain pan can typically be repaired. More serious damage usually requires replacing the pan. However, this is not possible on all furnaces as some units have the drain pan welded in place. In this case, the only option that remains is to replace the entire furnace.

If you notice water pooling around your furnace, one of the first things you should do is inspect all of the drainpipes. This is because there is always a chance that one of the pipes is damaged or a fitting between two sections of pipe is no longer properly sealed. If this is the case, the problem can quickly be solved by having a technician repair or replace the drainpipe.

If your condensate line empties out into a floor drain, there is also a possibility that this drain itself is clogged. This is something that you can easily test for by trying to pour water down the drain. If the drain is clogged, then you will either need to clear the clog with a drain cleaner or hire a plumber to unclog it for you.

How to Prevent Condensing Furnaces From Leaking

The best and easiest way to ensure that a condensing furnace doesn’t start leaking is to have it professionally maintained every fall before you turn it on for the first time. Furnace maintenance involves inspecting and cleaning all of the unit’s components, and this includes clearing the condensate drain system on condensing units.

You can also help to prevent mold and algae by occasionally pouring vinegar or hot (not boiling) water down the drain pipe. The system should be set up so that there is a cap located near where the pipe exits the furnace that allows access to the drain line.

An even easier way to accomplish the same thing is by using drain pan tablets, which work to prevent sludge and algae from forming. All you need to do is put one tablet into the drain pan every month, and it should help ensure that your drain system doesn’t become clogged.

Vancouver’s HVAC Experts

If you’re noticing leaking or experiencing any other issues that decrease the lifespan of a furnace, Western Pacific Heating, Cooling & Airflow is here to help. We repair and service all makes, models and brands of furnaces as well as air conditioners, heat pumps and other HVAC units. If you need to have your furnace or AC replaced, we specialize in residential and commercial heating and cooling installation as well as water heater and air purification services. Contact Western Pacific Heating, Cooling & Airflow today!

Western Pacific Heating, Cooling & Airflow

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