Why Is My Furnace Leaking on the Floor?

October 15, 2023

Every homeowner in Michigan needs a reliable furnace. Here, we depend on our HVAC systems to keep us warm in the cold winters and cool in the hot summers. Normally, your furnace should not leak water. If you check your furnace and see water around it, you know there is a problem.

The first question you probably ask yourself is, why is my furnace leaking on the floor? Furnaces have many components that require maintenance to keep them working properly. Understanding these parts can help you identify the issue and determine the right repair. Here are five common reasons that might explain why your furnace is leaking.

1. Condensation and the Drain Hose

If you live in the Greater Metro Detroit area, you are used to tough weather conditions. During the fall and winter, you need your furnace to keep your home warm and comfortable. Yet, using the furnace more can lead to condensation buildup within it.

The top reason why your furnace is leaking could be that condensation has blocked the drain hose. This is a very common problem with high-efficiency furnaces or those that have a 90% or higher annual fuel utilization efficiency (AFUE) rating.

High-efficiency furnaces are great because they have a second heat exchanger that converts fuel to heat more efficiently, provides additional heating power, and lowers costs. But these furnaces are also known to produce condensation, which is why they are also called condensing furnaces.

The second heat exchanger burns fuel longer and more efficiently, which means the gas produced has time to cool down before being expelled. This is why condensation develops.

The more you use your furnace, the more condensation it produces. This condensation is meant to be drained away in a condensate drain hose or line. Yet, condensation buildup can clog this hose and result in water spilling out of the bottom of your furnace.

As you rely more on your furnace to heat your home, condensation often builds up and can create a blockage. You can blame it on weather and long-term use, but maintenance or repair is probably required if you see water on the floor.

If your furnace is frequently turning on and off, and there’s water on the floor, the most likely reason is water condensation buildup. It’s best to get your furnace checked by a professional. Not attending to the leaking water can lead to larger issues with your furnace and the rest of your HVAC system.

2. Leak in the Condensate Pump or Floor Drain

As with the drain hose, the condensate pump in your furnace can get clogged and leak water. In furnaces, condensation and water are supposed to drain down through the drain hose into the condensate pump and the floor drain. Yet, if the condensate pump or drain gets blocked, a leak will result.

Condensate pumps are located where condensation and excess water are meant to drain. These pumps are designed to pump and lift water away into a floor drain. When a blocked pump or drain disrupts this process, the furnace will leak.

A pump that is also not working properly for another reason can make water build up and leak on the floor. Both water on the floor and rust stains on the furnace cabinet are signs that the condensate pump is not operating the way it should.

Like the drain hose, it’s best to have these pumps repaired or replaced if you see these conditions. Condensate pumps usually last three to five years. If your pump is more than five years old, that is a likely reason for your water leakage.

3. Humidifier Issues

Furnaces can come with built-in humidifiers. If this humidifier has a leak, that could also explain why there is water on your floor. Water is supposed to drain out of the humidifier, but if a crack or leak occurs, the water runs out instead.

Cold weather leads to low humidity. Humidifiers are often attached to furnaces to provide moisture in the air during the cold winter months. If your humidifier has a broken part or a clog inside of it, it will produce water. Conventional or standard efficiency furnaces are prone to humidifier malfunctions, including cracks in the water lines. If you have a conventional furnace, this may be the first thing to check for.

Humidifiers can also have minerals and other debris build up over time and create a blockage. Having a humidifier with your furnace is a helpful part of your HVAC system, but it could also be the reason why you’re seeing water on the floor.

4. Furnace Filter

As in a car, the filter in your furnace is another one of its essential parts. A dirty or clogged furnace filter could lead to the water you see on the floor. Dirt and debris can get caught in the filter, which can lead to reduced airflow through your furnace’s evaporator coil. In turn, too much moisture or ice can build up on the coil and eventually drip to the floor below your furnace.

An unclean filter can lead to water leakage and larger problems with your furnace and HVAC system. For these reasons, the filter is another possible cause of a leaking furnace.

5. Furnace Exhaust Pipe

The furnace exhaust pipe is the final possible reason for the water on your floor. This part is also referred to as the flue pipe, and it is in charge of venting the gas exhaust from your furnace to the outdoors.

A high-efficiency furnace uses a white plastic (PVC) exhaust pipe, which could have cracked or become clogged. Under normal conditions, when your high-efficiency furnace releases exhaust gas, it also creates condensation. This moisture is usually released through the exhaust pipe, but a damaged exhaust pipe often results in water leakage.

Exhaust pipes also may not fit correctly, and sometimes, they are not placed in the appropriate upward position. Either of these situations can also explain the issue and are common with conventional furnaces.

Standard efficiency or conventional furnaces come with metal exhaust pipes and usually do not produce condensation or leak through a hole or crack. So, if you have a conventional furnace, the issue may be with the placement of the pipe, not the pipe itself.

If the culprit is your exhaust pipe, there could be other indications, such as condensation building up on a window or rust near the pipe. A professional can determine if this is the case and replace the part.

Rely on Us for Furnace Repair Services You Can Trust

Feel free to contact us at C & C Heating and Air Conditioning for more information on keeping your furnace in top condition. Based in Roseville, we provide furnace repair, maintenance, and installation to the Detroit metro area counties of Macomb, Oakland, Washtenaw, and Wayne. We also offer HVAC cleaning and replacement and AC services. We are here for all your HVAC needs.

company icon