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One of the most common issues on home furnace systems is a leak. A furnace leak can occur at any point in home ownership, but it is most likely to occur for those that are ill-maintained. The troubling thing about furnace leaks is that apart from their impact on the home heating system, they could also cause water damage in the house. Water damage leads to mold and mildew growth. Mold growth can cause a throng of illnesses including bronchial allergies, allergic rhinitis, skin sensitivities, and headaches, among other symptoms.

Given the above-mentioned issues that are likely to occur, it is in the best interest of every homeowner to have his leaking furnace fixed to avoid other issues. When furnaces get leaky, and this issue continues to drag on without professional repair the problem gets even more complicated and costly to address.

This article will discuss the possible reasons why a furnace would leak water, and round up ways to deal with and avoid it.

How does a furnace work?

Before diving into the reasons why a furnace would suddenly leak water, it is best to discuss first the basics of a furnace operation. Furnaces usually start working once the thermostat detects a dip in the desired temperature indoors. Once the temperature goes lower than the thermostat settings, it will signal the control board to commence the heating cycle. The cycle begins by opening the gas valve and switching on the draft fan which in turn paves the way for combustion. Once the combustion heats the heat exchanger, the flue gasses within will get released via the exhaust pipe. A furnace may also have auxiliary heat that is shown on the thermostat, find out what to do if auxiliary heat is shown on thermostat.

From here the blower forces the cool air from inside the house to go past the heat exchanger. This process makes that cold air absorb the heat. Once the air is warmed, it gets forced back into the house through the vents. This continuous process ensures that the house stays warm according to the preferred temperature of the homeowner.

So why will a furnace leak water?

There are two basic types of furnaces. The conventional, which is also known as a non-condensing furnace, and then the High-Efficiency furnace which produces condensation through its second heat exchanger.

Unlike standard efficiency furnaces, High-Efficiency furnaces have two heat exchangers. Since the gasses are further heated in the second heat exchanger, water vapors form leading to condensation. Due to the condensation that takes place, the air gets heated even further, making high-efficiency furnaces, even better at heating. The condensation then exits the system through the floor drain or the condensate pump.

Determining the type of furnace

It is relatively easy to know the type of furnace used in a property. This is usually determined by the type of exhaust pipe. A plastic PVC pipe for instance means that it is a condensing furnace. If the exhaust pipe is made of metal, then it is a standard efficiency furnace. Standard or conventional furnaces do not form water vapors that lead to condensation.

Why will a high-efficiency furnace leak water?

Normally, high-efficiency furnaces do not leak excess water. The condensation formed in the heat exchanger gets expelled through a condensation pump or a floor drain. But when there is a clog somewhere, or the pump malfunctions then the furnace could leak water.

Below are some examples of how water could leak from the furnace:

  • Condensate drain hose leak. Water commonly leaks because of a clog in the condensate drain hose. Over time, the pipes could get slimy, grimy, and even moldy. Dust and debris could accumulate and so condensation could not correctly get expelled within the system, leading to water leaks. It is also likely that the drain hose could get dislodged, cracked, disconnected, or sustain any type of damage.
  • Condensate drain line leakage. It is also possible that furnaces would leak water due to an issue within the condensate drain line. Sometimes it loses its connection, sometimes it could incur damage, or sometimes it gets holes in it and so water will flow through that and leak. 
  • Inducer assembly leak. The inducer assembly is last in the line where the condensation will pass through. After water vapor is formed in the exchanger, it runs down the flue pipe, then through the condensate drain hose, and lastly to the inducer assembly. Unfortunately, the inducer assembly could sustain damage at one point, and commonly these are cracks. Water can seep through these cracks and appear as a leak.
  • Condensate trap issue. While not all furnaces have a condensate trap, those that do could back up and overflow. When the traps are clogged, water will eventually leak as the trap gets overfilled.
  • Leaking condensate pump. Condensate pumps can get clogged, giving way to furnace water leaks. This is the case if the homeowner notices water pooling on the floor of the furnace, or sees rust forming near the cabinet. Since the condensate pump is clogged, water could not properly drain out of the system.

 If the condensate pump is not clogged but is malfunctioning then it is also likely that it is already worn out. Condensate pumps have a life span of 3-5 years, any longer than that, it is sure to wear out soon. Once it fails, water will surely back up into the system and leak through. For this reason, regular professional tune-ups are essential to prevent ill-timed furnace breakdowns.

Why will a non-high-efficiency furnace suddenly leak?

Standard efficiency or conventional furnaces do not usually leak water. Most likely, the leaks that appear to be coming from it are instead from another appliance adjacent to it. For instance, the leak may be coming from the air conditioner. If you also want to know why a pilot light keeps going out and how to fix it you can read more here.

Water is leaking from the air conditioner

The AC can leak due to several reasons. The most common culprit include clogs, frozen evaporator coils, drain line issues, damage in the drain pan, and more. Check below for a brief discussion on each of the common reasons why air conditioners could leak water:

  • Drain pan damage. A damaged drain pan can cause water leaks if it has a crack or hole. The drain pan is usually situated underneath the evaporator coil t catch condensation, and then beneath that is a secondary drain pan, although not all units may have it. If any of these drain pans are cracked or get a hole then water will surely overflow.
  • Frozen evaporator coils. Evaporator coils get frozen when there is something wrong with the airflow or refrigerant levels. When this occurs, water will surely leak through especially when the ice gets thawed.
  • Clogged drain line. Like a high-efficiency furnace, air conditioners also have a drain line. Once this line gets blocked with dust, debris, mildew, or whatnot, it will result in spillage that makes water leak through the system.
  • Condensate Pump failure. HVAC systems do have a condensate pump, and if this malfunctions, water will overflow and leak through the system.

Water is leaking from the water heater

Apart from the air conditioner, it is also possible that water is leaking from the water heater. If the water heater has a crack or if it has drain valve issues then water will surely leak from it. Unfortunately, if it is installed next to the furnace, then homeowners could think of the pooling water to be coming from it.

The water leak is coming from the humidifier

It is also possible that the leak is coming from the humidifier. Some homes that have a whole-house humidifying system could experience this. If the humidifier is installed next to the furnace then it is easy to think that the water is coming from the furnace instead.

The built-in humidifier within an HVAC system could spill water when there is an issue with the water supplied to it through the plumbing system. The issue occurs when the water line is damaged, corroded, cracked, or gets blocked due to ill-maintenance.

Is a leaking furnace dangerous?

A furnace that is leaking water does not pose an immediate threat to safety, as opposed to gas leaks. However, if servicing is postponed it could surely have an impact on the comfort levels around the house and could also worsen the existing problem. Leaving this issue unaddressed could result in more expensive and more complicated repairs.

The initial consequence of water leaks is rust. Rust can lead to several issues, including the corrosion or decaying of otherwise working parts of the furnace system. When this occurs, the furnace becomes less efficient, and eventually breaks down.

Likewise, the location of the rusting can also have an impact on the degree of damage that could occur to the furnace. For instance, the worst place where it could occur is in the heat exchanger. If the rusting could cause a hole or damage there then dangerous carbon monoxide gasses can seep through the hose and present an imminent threat to the health and safety of everyone in the household.

Moreover, water leaking from the furnace could drip through internal components within the furnace system. When any of the electrical fixtures get wet, the furnace could malfunction. For instance, if the circuit board is subjected to a water leak then it could fail to give correct functioning signals to the furnace components. Besides, if water gets into the control board, it will not be long until it would need to get replaced.

The best thing to do upon discovering water leaks from the furnace is to immediately call for professional help. The consequences would not be great in terms of overall comfort, and the complicated and expensive repairs can be stressful. Do not shrug this issue off.

What to do if the furnace is leaking water

Step 1: Do not panic. Instead, turn off the power from the furnace or the HVAC system. Switching off the power would stop water from leaking further. This can be done either through the thermostat, the switch next to the furnace, or the breaker panel.

Step 2: Remove the water that leaked. Mop or clean with a rug, the water that spilled because of the leak. If the water level is substantial then using a wet vac is a good idea.

Step 3: Remove the front panel of the furnace. Remove or unscrew the front panel of the furnace system to remove the water that got spilled inside because of the leak. Although the leak is not visible from the outside, this step is important to prevent mold from growing inside the furnace.

Step 4: Call up an HVAC professional, like us at Reliable Standard Heating and Repair.

How can I prevent the furnace from leaking in the future?

After going through the repairs and inconveniences of a furnace that is leaking water, it is important to know what to do moving forward to avoid a recurrence of the issue. Fortunately, there are easy steps to take to make sure that this will not happen again. Scheduling a professional tune-up on a routine basis is the key to preventing future leaks. Furnace technicians or HVAC professionals can easily spot possible issues and repair them even before they become full-blown issues.

Schedule an appointment for a furnace tune-up if it has been more than six months since the last one. HVAC maintenance checks must be carried out twice a year – once before the heating season, and again before the cooling season commences.

We got you covered!

At Reliable Standard Heating and Air, we make sure that you and your family remain comfortable throughout the seasons of the year! We have helped countless San Diego homes and businesses resolve leaking furnace issues and made sure that the issue will not recur.  

We will be more than happy to offer you regular furnace tune-ups that will ensure your home heating system will not break down on the chilliest of nights. We can also offer you our furnace or HVAC maintenance plan that automatically schedules bi-annual tune-ups so that they are never forgotten. This package helps you prolong the life of your furnace and AC, ensures they work at optimal levels and helps maintain heating or cooling efficiency warding off unnecessary spikes in utility bills. Moreover, subscribing to this maintenance plan gives you priority repair appointments, waived emergency servicing fees, and discounts on parts and supplies. Get in touch with us today!

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