High Efficiency Furnace Condensate Drain (2022)

The secondary heat exchanger produces water. It collects in a collection box before flowing by gravity through a sloped drain tube. The high efficiency furnace condensate drainis required to release outside the home properly. This design includes a drain trap that allows free drainage. It prevents dangerous combustion gases from escaping the furnace.

The humidity on the evaporator coil either drains naturally or is forced out of the air conditioner. It is done through the condensate drain, a short PVC pipe. A small clog in your condensate drain may quickly become a major issue!

High Efficiency Furnace Condensate Drain (1)

Furnace Condensate Drain

That condensation must be drained out for the furnace to function effectively. Otherwise, it will build up inside the heat exchanger, inducer, and venting. It will obstruct the normal gas/combustion flow of products. Almost all furnaces have at least two internal drains. One is for the heat exchanger and one for the vent. These are commonly located at the inducer outlet or on the activator enclosure.

(Video) Furnace Troubleshooting Condensate Piping

A sensor detects an obstruction inside the furnace’s drain tube. The furnace is automatically switched off as a safety precaution. Here condensation pan switch will help you a lot. To restart the furnace help, restore heating, the blockage must be located and cleared. As well as the drain trap checked and cleaned.

How to Access Furnace Condensate Drain Pipe?

A condensate drain pan is always positioned with your system’s evaporator coils due to the nature of its functions. The location of these components is determined by the type of furnace or air handler you have installed in your home.

High Efficiency Furnace Condensate Drain (2)

The furnace or air handler is in an upright position in a vertical application. The drain pan is situated just below because the evaporator coils are near the top of the unit in a vertical installation.

The furnace or air handling unit is mounted on its sides in a horizontal application due to the restricted space available in this location, dependent on roof pitch. This installation application is most commonly encountered when the unit needs to be installed in an attic. The airflow travels from side to side rather than up and down when the device has mounted this manner. The evaporator coils are near the return air ducts next to the furnace or air handling unit, and the condensate drain pan is below it.

(Video) How to install a drain line for high effecient furnaces.

Clogged Condensate Drain Line

Mold and mildew may grow in a damp environment. The drain pan becomes clogged as a result of these impurities, as well as particles in the air. These obstruct the operation of adrain pan. It is done by stopping the passage of moisture to the drain line and out of the house. Moisture backup is the end outcome. Water supports into the network depending on the orientation of your HVAC equipment. As a result, component damage occurs. Water pours over the borders of the Furnace condensate drain line in this situation, causing damage to the area around your HVAC system. Don’t put yourself at risk of mold and water damage. These are frequently high-cost restoration operations.

High Efficiency Furnace Condensate Drain (3)

When the line is entirely stopped, you may see distressing indicators of water leaks in your home. That is difficult to identify from a plumbing or roof leak. When the condensate pan overflows, this can corrode metal elements of your mechanical devices. Create drywall, carpentry, and flooring damage costing hundreds of dollars. A clogged condensate line can reduce the efficiency of your high-efficiency HVAC system. It will also cause musty aromas from algae and mold.

All condensate drains are collected in a trap. For a high-efficiency gas furnace, condensate traps are required. The drain connects to the exhaust system. Leaving it exposed to the air could result in an exhaust gas leak in the living area. Furthermore, if the inducer motor weren’t caught, it would suck air through the drain. It will affect combustion and prevent correct drainage.

How to Unclog Furnace Condensate Drain?

Your experienced HVAC technician will flush the condenser drain to remove blockages. Such as pet hair, dirt, insects, and leaves during an annual preventive tune-up. You can resist subsequent obstructions by doing the following chores regularly:

(Video) Clean the condensate drain of the 90% gas furnace

  • Clean the area around your indoor unit with a vacuum to remove any dirt or debris that may have made its way into the drain.
  • Keep the area all around the drain’s end clean and clear of debris. Remove leaves and another removal from drain’s terminus regularly if it terminates outside.
  • If the condensate drain becomes plugged, turn off the electricity to your air conditioner at the main circuit breaker. Using a wet/dry vacuum, remove any standing water from the condensate pan. Insert a plumber’s cable or rubber tubing into the PVC drain connecting to the pan to remove obstacles. Then do the same with the drain’s ends.

Why Pay Attention to Condensate Drain Pan?

Your air conditioning system will freeze if a line becomes clogged. Water will be trapped in your air conditioner due to a clogged condensate drain tube. The evaporator coil will eventually freeze to ice as a result of this. The moisture in the drain line can freeze, causing your air conditioner to shut down. But, before it does, it will very certainly be damaged. That is why it is critical to inspect the drain line at least once a month. The Drain Pain will overflow due to a clogged line.

If you do not even know where is the line? Look underneath the AC system’s evaporator coil, the inside unit. After extracting moisture from the air, your air conditioning system deposits it in the pans before draining it down the condensate line. If the line clogs, the drain pan will overflow, allowing microbial growth to flourish.

Other Symptoms of Condensate Pan Issues

These signs also signal the presence of a problem to homeowners:

  • In the home, there is more humidity.
  • The HVAC system emits odors.
  • Mold spores
  • Increased energy costs
  • There is no water in the line.

Ac Condensate Drain Line

The condensate line should drain to the outside. You should notice plenty of water pouring from it during humid conditions. There’s a problem if the water drips someplace else. Check for moisture or exhaust fans coming from the panel’s bottom. Your condensate drain is clogged if you see standing water inside the drain pan! Quickly take action if you observe any water stains or damage to the ceilings, flooring, or furnishings near the Ac. When an air conditioning system is installed above a furnace, the furnace may develop rust. Here are some precautions:

  • Ensure that all condensate-producing components are angled toward the drain. That entails slanting the venting down towards the furnace, as well as slanting the furnace itself! Check your installation handbook. Most manufacturers recommend installing the furnace with a modest forward slant. It helps to allow condensate to drain from the heat exchanger.
  • Slope the drain line properly. To minimize airlocks, avoid double trapping and vent the drain after the trap.
  • It’s best not to run the drain in an area where it might freeze. This includes, if one exists, running it through the natural fresh air inlet.

How Condensate Drain Line Works

Condensation is produced by heating and cooling equipment. The evaporator coils in an interior HVAC system drop to low temperatures. And become cold when the cooling process begins. As a result, the coil can absorb the heat from the entering air and cool it.

(Video) Make your own condensate neutralizer

The wet warm air from your house enters your unit. But as heat is transferred through the evaporator coils, the moisture is eliminated. Condensation accumulates along with the evaporator coils as the AC collects moisture from the indoor air during the heat transmission process. A condensate drain pan collects the water that drips from the evaporator coils of your air conditioner.

Below the evaporator coils is where the condensate pan is mounted. It must be properly installed to catch humidity and prevent leaks. Moisture drains out of your home through the condensate drain line. Excess moisture from your home’s air is allowed to exit your home through the condensate pan. The cooling process leaves you with the extra benefit of moisture control indoors.

Other Damage Can Result From a Blocked Line

The damage caused by adrain line isn’t limited to your ac system. An overflowing drain pan can cause drywall damage, major leaks, and electrical wiring destruction. Pour cup liquid bleach into the drain line’s entrance to prevent clogging. And when the matter gets out of hand, just make sure to contact the best Air conditioner repair contractor.


Your furnace condensate drain line enables moisture to escape the device and into your home. A properly working condensate drain network keeps water out of your HVAC system and your home. Know how your condensate pan works and when to seek professional assistance.


How much condensation should come out of furnace? ›

If the rating is 90 percent or more, your furnace has a cool exhaust and produces condensation, therefore, it is defined as high efficiency. On the other hand, if your furnace has a metal exhaust pipe, it is a standard-efficiency furnace and should not have condensation. It will have an AFUE below 90 percent.

How much condensate does a high efficiency furnace produce? ›

HomeTips.com says a high-efficiency furnace can produce as much as 5 or 6 gallons of water from condensation each day. Most of the time, condensate pipes are set up to carry condensation outdoors through a hole in an exterior wall. The water is able to drain harmlessly into the ground.

Does a high efficiency furnace need a drain? ›

A high-efficiency furnace (also called a condensing furnace) will always have condensation as a byproduct of heating your home. A floor drain is necessary for your high-efficiency furnace because the water has to go somewhere and a floor drain is the easiest and most effective outlet.

Does a furnace need a condensate drain? ›

The condensate trap is absolutely mandatory for a high-efficiency gas furnace. Since the drain taps into the exhaust system, leaving it open to the air would allow for a potential exhaust/flue gas leak in the living space, which is a big no-no.

How much water should come out of the condensate pipe? ›

A typical hour-long operation of your boiler may produce around 2 or 3 litres of the condensate water waste. This waste generally gets released in 300ml increments, and is often the reason you might hear water travelling through your pipes during intervals.

Why is my furnace producing so much condensation? ›

Causes of Furnace Leaks

This can be the result of clogged condensation tubing, breaks in the condensation line or other possible issues with the pump. Humidifier issues are also a possible cause of furnace leaks. A clogged filter or drain in the humidifier can easily cause any furnace to produce unwanted moisture.

Does a high efficiency furnace need a condensate pump? ›

Condensate pumps are used to effectively direct and remove excess water from high efficiency furnaces (as well as humidifiers and A/C units). The pump takes the place of hoses that can and do rupture, and seamlessly transfers water to the appropriate drainage pipe.

Where should I run my condensate drain line? ›

The final place to drain your condensate line is the drain line access point. The access point is most often located inside the home near the indoor air conditioner unit. This access point will also be covered with a PVC cap. Pour hot water or vinegar into the access point to flush the drain line from the inside.

Do high efficiency furnaces create condensation? ›

High efficiency furnaces produce high amounts of condensation moisture in the exhaust vent, which is designed to run back into and through the furnace in order to drain out into either a floor drain or other approved draining system.

Do high efficiency furnaces leak water? ›

When these gases cool down, they also create condensation, which is exactly what makes them more prone to leaking. This condensation means that high-efficiency furnaces need a way to drain the water away from the system. This is accomplished through the use of a drain line, drain pan and floor drain.

Can you drain furnace condensate outside? ›

A furnace produces condensate as it works (it's part of the combustion process), and this condensate must be drained and removed to the outside. If the pipe that runs the condensate to the outside of the house freezes over, your furnace won't be able to work!

Is high efficiency furnace condensate acidic? ›

High efficiency furnaces and water heaters have drains for condensation. The problem is the acidity of the condensation. Condensate formed from combustion gas is extremely acidic and therefore very corrosive. It can eat through copper piping in a matter of months and through cast iron drains in just a year or so.

How much condensation does a gas furnace produce? ›

A furnace can form as much as five or six gallons of water from condensation each day. Usually, condensate pipes are set up to carry condensation outdoors through a void in an external wall through which the water can drain harmlessly into the ground.

What temperature is furnace condensate? ›

“Condensing” furnaces and boilers are so named because they utilize an added “secondary” (typically finned tube) heat exchanger to extract additional heat from the flue gases, reducing flue gas temperature from a typical 500-600°F to around 100°F, and removing the “latent heat of vaporization”, which is the heat ...

Can you vent a high efficiency furnace through the chimney? ›

These high efficiency units use PVC pipe to pull air in for combustion and vent the by-products to the outdoors. Your furnace won't exhaust gases into your chimney anymore. Instead, an HVAC contractor will install the system to expel the exhaust directly outside your home.

Why is water coming out of my condensate pipe? ›

If you see water coming out of a pipe on the side or rear of your home up high, it means your main condensate line is clogged and you need to call for AC service right away.

How much water does a condensate boiler produce? ›

An efficient condensing boiler will generate around 2 litres of condensate water an hour at a temperature of around 30-40°c. This needs to be safely disposed of, within the buildings waste water system.

How much condensate does a boiler produce per day? ›

According to the HHIC (Heating & Hot Water Industry Council), a condensing boiler that's working efficiently will produce around two litres of condensate water every hour.

How do I stop condensation in my furnace vent? ›

How to Mediate Flue Condensation
  1. Adjust the furnace temperature: Make sure that the furnace temperature is hot enough for the gases to freely flow through the flue and out into the atmosphere.
  2. Improve the flue design: Have a professional HVAC tech look at your flue and recommend improvements to the flue's design.
22 Apr 2020

Why is there water on the floor around my furnace? ›

If your furnace's filter is dirty and clogged, it will restrict airflow through the furnace coil. Many times this causes the coil to freeze. However, sometimes it causes water to leak and pool up around the furnace. Make sure you always check the condition of your furnace's air filter and replace it if it's dirty.

Why is there a puddle of water under my furnace? ›

The most common reason for water under your furnace is a clogged condensation drain. Condensate is the name given to the moisture that has been condensed out of the air in your home when the air conditioner is running. once it turns the humidity into water, it ha s to get rid of it.

Is a condensate pump necessary? ›

Without a condensate drain pump, moisture may fail to properly drain from the condensate pan. Some AC systems are installed in basements or crawlspaces. With the evaporator coil being lower than the ground level, a condensate drain pump is required.

What happens if furnace condensate pump fails? ›

If the condensate pump isn't working correctly, it's dangerous to run your air conditioning system because it can cause water damage and other costly repairs in the long run. Knowing how to troubleshoot a broken condensate pump is essential to ensure your system gets the repairs it needs before a bigger issue occurs.

How long does a furnace condensate pump last? ›

Typically, the lifespan of a water pump is between two and three years, though this depends on the quality and brand of the pump. Your usage can also affect how long your condensate pump lasts. If your HVAC system is constantly exposed to debris and dirt, your pump may need replacement sooner than expected.

How long can a condensate pipe be? ›

The external pipe run should be kept as short as possible to a maximum of 3 metres, taking the most direct and “most vertical” route to the discharge point, with no horizontal sections in which condensate might collect.

Does condensate drain need a vent? ›

no vent. per se, is required on the condensate line itself, unlike sanitary drains, which must be vented to prevent siphonage at the traps and possible collaspe of the sewer pipe due to possible negative pressures created when no vent is present.

Can you run a condensate pipe into a waste pipe? ›

Yes, a condensate pipe can be routed into a waste pipe. This is best done after the trap on the waste pipe in case of blockages.

Do high-efficiency furnaces dehumidify? ›

High-efficiency furnaces, also called a sealed combustion furnace, are better at keeping your humidity even. They take all their combustion air from your home's exterior, but it stays contained inside the sealed furnace. As an extra bonus, they keep your home more comfortable while using less energy.

How many years does a high-efficiency furnace last? ›

A well-maintained furnace can last at least 15 to 20 years, but completing annual maintenance and being diligent with repairs can extend its life even longer.

Does a furnace need a floor drain? ›

Without proper drainage, that condensation from your furnace would accumulate in the heat exchanger and in the vent, making it difficult to heat the air properly. In fact, many high-efficiency furnaces have two drains: one in the secondary heat exchanger and one in the vent.

Where do you drain a high efficiency furnace? ›

Then there's the obvious answer: drain the furnace condensate into the sewer line instead of pumping it outside the house.

How do you winterize a high efficiency furnace? ›

  1. Clean Or Replace The Filter. ...
  2. Vacuum The Furnace Interior. ...
  3. Check The Blower Belt And Oil The Blower Motor. ...
  4. Make Sure Blower Doors Are Replaced Properly. ...
  5. Check To See If Vents Are Unobstructed. ...
  6. Check The Exhaust Flue. ...
  7. Contact Horizon Services.
11 Oct 2013

Where does furnace condensate drain go? ›

The condensate drains out through a pipe, usually on the bottom of the furnace. Most high-efficiency furnaces also have a secondary drain line that comes out of the flue pipe. This secondary line is used to drain any residual moisture so it doesn't leak into your furnace.

Is furnace condensate water toxic? ›

Furnace condensate is not a toxic liquid; however, it is an acidic solution that consists of water, carbon dioxide, nitric acid, and, in some cases, traces of metal, mold, and mildew. This condensate is corrosive and has to be neutralized before getting drained into the wastewater system.

How often do you change condensate neutralizer? ›

The neutralizing media should be replaced when the pH level drops below the minimum level of the local water authority, when the float rises (see figure 4 below), or after one year, whichever comes first.

What pH should condensate be? ›

Most condensate from natural gas appliances will have a pH of between 2.0 and 4 with 7 being neutral. The actual pH will vary according to the actual chemical makeup of the fuel that is being burned.

How much condensate does a condensing furnace produce? ›

The amount of condensate produced by a high-efficiency furnace is approximately 1 gallon per 100,000 Btu/h. For example, a 150,000 Btu furnace running eight hours per day would create 11 gallons of condensate.

How do I stop condensation in my furnace vent? ›

How to Mediate Flue Condensation
  1. Adjust the furnace temperature: Make sure that the furnace temperature is hot enough for the gases to freely flow through the flue and out into the atmosphere.
  2. Improve the flue design: Have a professional HVAC tech look at your flue and recommend improvements to the flue's design.
22 Apr 2020

Why do I have water leaking from my furnace? ›

Water leaking from a conventional furnace is typically a symptom of either a malfunction with the built-in humidifier or an ill-fitted exhaust pipe. The humidifier empties excess water through the furnace drain line. If the drain line is clogged, the water will build up, leaking from the humidifier into the furnace.

Does heating produce condensation? ›

Furnace Condensation and High-Efficiency Furnaces

When all the heat is extracted from the combustion gases, they condense to a liquid, and since water vapor (surprisingly enough) is one of the main byproducts of combustion, the condensate is mostly water.

Why does a high efficiency furnace produce water? ›

Although a furnace doesn't use water to run, special high efficiency furnace produces condensation during combustion. This is because a high-efficiency furnace collects vapor in the heat exchanger from the cooled-off combustion gas rather than venting the gases out a flue.

Do high efficiency furnaces produce water? ›

A conventional furnace, also known as a standard efficiency furnace, does not produce water. However, if you have a high efficiency furnace, (90 % efficiency), condensation will arise due to the addition of the second heat exchanger.

Can you drain furnace condensate outside? ›

A furnace produces condensate as it works (it's part of the combustion process), and this condensate must be drained and removed to the outside. If the pipe that runs the condensate to the outside of the house freezes over, your furnace won't be able to work!

Is it normal to have condensation on air vents? ›

Occasional condensation on A/C ducts is not a problem, but keeping an eye on the situation is recommended. Persistent ductwork sweating may eventually lead to water damage. Excessive condensation can also create conditions favorable to mold or mildew forming in areas surrounding the duct itself.

Where do you drain the condensate line on a furnace? ›

It may be located directly under the indoor air handler in your attic or utility closet. It may be covered by a removable access panel. If there is standing water in the condensate pan, your drain line is probably clogged.

Why is my air vent dripping water? ›

Clogged Condensate Drain Line

The problem: If condensation accumulates within the air vent, it can cause water to drip from the AC vents. This is often caused if you have a clogged condensate drain line on your hands.

Can a furnace leak a lot of water? ›

Leaks are a fairly common issue for furnaces. There are a number of reasons they happen; some major, others minor. If you come home to a furnace leaking water, you'll most likely need a technician to come out and diagnose the problem. But it never hurts to stay educated on the different components of your home.

What is the small pipe on the side of house dripping water? ›

AC Drain Lines and Water Heater PRV Lines

The two most common drain pipes that most people have on the side of their house are: Air conditioner condensate lines (AC drain line). Water heater pressure relief valve lines (PRV drain line).

How much water does a furnace drain? ›

A furnace can form as much as five or six gallons of water from condensation each day. Usually, condensate pipes are set up to carry condensation outdoors through a void in an external wall through which the water can drain harmlessly into the ground.

What temperature should I keep my house to prevent condensation? ›

The World Health Organisation guidelines suggest 21 degrees in a living room and 18 degrees in the bedrooms, falling lower at night and when you are out.

What temp does condensation occur? ›

Condensation occurs when the water vapor in the air is cooled, changing from a gas to a liquid. This process can take place at various temperatures between 32 and 212 degrees Fahrenheit, or 0 and 100 degrees Celsius.


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3. Video No.2- Furnace Drainage Installation
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6. Why Does My Furnace Leak Water? Can I Fix It?
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