Why is My Furnace Leaking

Nov 5, 2019 | Furnace

Cooler weather has arrived, and soon it will be time to fire up your furnace. As you are giving things a quick once over, checking your furnace’s air filter and making sure the area around your furnace is clean and clutter-free, keep an eye out for any signs of water leaks. Any indication of leakage needs to be addressed right away in order to prevent serious damage to your heating system. There are a number of common issues that can be responsible for leaks but do not try to identify and correct them yourself. Contact a trained HVAC technician immediately to keep your furnace from suffering serious or permanent damage.

There are two basic types of furnaces: conventional and high efficiency. Regardless of which type you have all furnaces have a pipe that carries condensed water out of your heating unit. This is called the vent pipe. If you are uncertain as to which type of furnace you have, a quick glance at the vent pipe will tell you. If the vent pipe is metal, then you have a conventional style furnace. A white PVC vent pipe means that your furnace is a high-efficiency style. Different issues can affect each one, resulting in water leaks.

If you have a conventional furnace one of these issues may be causing a leak:



A vent pipe’s main function is to carry away the gases that result from the furnace’s combustion process before they can cool down and leave condensation inside. If there is a problem with the design of the vent pipe (too large, not curved or sloped enough), then air will get inside and trap the gases. When this happens, the gases are unable the

flow through the pipe and out and away from the furnace. If they stay in the vent pipe condensation occurs and the water leaks into other parts of the furnace, potentially causing serious damage to your heating system.



All furnaces have a humidifier to infuse into the warm air that it circulates throughout your home. A leaky humidifier can cause major problems within your heating system. You can locate the humidifier easily. It is a small device that is attached to your furnace and has hookups for water, drainage, and electricity. If the drain or filter of the humidifier becomes clogged, then water can back up into your furnace and cause damage to your furnace.

If you have a high-efficiency furnace, a water leak can result from one of these issues:


A Clogged Drain Cover

If you discover a leak, check the easy fixes first. Look at the drain cover, also called the trap, where the water flows out and away from your furnace. This is where dirt and debris can build up and clog the trap, causing the water to back up into your furnace. This can be fixed by simply cleaning the drain cover with a shop-vac.


The Drain, Humidifier, Or Condensate Pump May Be The Problem

Older homes generally have floor drains. More modern homes most often do not. In cases where no floor drain is present near the furnace, a condensate pump is attached and a drain line is installed. The line is then run to the drain nearest the furnace. If the condensate pump becomes clogged, then the water has no way out and will back up into the drain and overflow into your furnace.

High-efficiency furnaces feature built-in humidifiers. If the humidifier gets clogged or if it develops a leak, this can lead to big problems for your system. The humidifier, water feed tube, and drain line are all found on the outside of the system. This makes it easy to see if a clog is the issue, but do not try to remove the blockage yourself. You may cause more damage. Instead, contact a professional HVAC technician right away.

The condensate drain is the main means of removal of your furnace’s excess water. This drain tube runs directly into a floor drain from the furnace so that water can be carried out and away. If the drain becomes clogged there is nowhere for the water to go. It will back up into the drain to the condenser pipe and then overflow into the furnace.

An annual inspection and cleaning of your HVAC system should always be performed before you begin using your furnace for the season. An HVAC professional will spot these issues and correct them before they can become serious. If you notice any leakage or other signs of a problem, contact an HVAC technician at once to avoid damage to your system.


At Xenia Heating and Air our fully-trained HVAC technicians are standing by, ready to make sure that your furnace is winter-ready and safe. Call us today to schedule a complete inspection and cleaning of your furnace and your entire system to ensure that everything is clean and in top working order. You can reach Xenia Heating and Air by phone at 937-708-8451, or on the web at www.xeniaheatingandair.com.