Should My Exterior AC Drain Pipe Be Dripping Water?

You just arrived home to find that your air conditioner’s drain pipe is dripping water. Initially, it was only a few drops that didn’t catch your attention. However, you now have a water pool under the drainpipe, which has left you very worried.

What’s wrong with the AC? Is something broken? Where does the water even come from and is it normal for the AC unit to produce so much water?

Unsurprisingly, you’re right to be worried. While the AC can sometimes generate water, which is why the condensate drain pipe is there in the first place, too much water is often a very bad sign. Read on to learn why your AC occasionally drips water, how much water is too much, and how to diagnose and fix the damping problem.

Should My Exterior AC Drain Pipe Be Dripping Water?

Yes, when it’s very hot outside. But not always. Why? Because although air conditioners naturally condense moisture, producing water, properly installed units have a dedicated condensate pipe that drains into the home’s sewerage system. The exterior drain pipe is often the emergency drain pan. So, there’s a problem if the backup drain pipe is dripping water.

How Air Conditioners Work

Let’s begin with a quick overview of how air conditioners work to understand where the water comes from and how much water a standard air conditioner produces on a normal day.

Air conditioners are primarily cooling appliances. They draw hot, musty indoor air, extract the heat from the air using very cold refrigerant, and then return the now-cool air to your home, gradually lowering the temperature of the home.

However, we often overlook the other role of the AC – humidification. As an AC removes heat from indoor air, it simultaneously removes moisture.

The Often-Overlooked Dehumidification Process

Air conditioners remove moisture from indoor spaces in two ways – naturally and through built-in dehumidifiers.

  • Natural dehumidification: An AC will remove moisture from your home (to a certain degree) naturally without an in-built dehumidifier. How? It’s straightforward. As we’ve already mentioned, the aircon’s refrigerant lines are very cold. Therefore, as hot return air from your home flows across the cold evaporator coils (containing the refrigerant), the moisture in the air will condense on the surfaces of the coils.
  • Dehumidification via built-in dehumidifiers: Several modern air conditioners are equipped with powerful built-in dehumidifiers to actively extract moisture from your indoor air. Of course, ACs with built-in dehumidifiers dehumidify the home faster.

Where Does the Condensation Go?

Where the condensed water goes often depends on the type of AC and whether it has a built-in dehumidifier.

Smaller air conditioners without built-in dehumidifiers typically have two tiny drain pans to hold the condensate temporarily. One drain pan is located in the indoor air handler to collect condensate from evaporator coils while the second one is in the outdoor unit to collect condensate from the condenser coils.

The condensate is usually very little that it naturally evaporates due to the constantly blowing fan and powerful airflow through the AC. Some units also have a fan sling to throw the condensate against the condenser, thus evaporating it.

Meanwhile, larger AC units use a combination of drain pans and drain lines. The pan collects the condensate, then the drain line lets it flow out of the unit through two condensate drain pipes during the cooling season.

The first drain pipe connects to the home’s main plumbing and is the primary condensate drainage solution. Meanwhile, the exterior drain pipe which sticks from your walls is the secondary drain line which only removes water if the primary drain pan is compromised or there’s too much water from your AC.

Should the Exterior AC Drain Pipe Drip Water Consistently?

It depends. As we’ve seen, smaller air conditioners may not even drip water in the first place. The condensate from the cold coils drips into the drain pan and naturally evaporates within minutes. So, you don’t even need a dedicated drain line.

However, larger air conditioners and units with a dedicated dehumidifier may drain water continually as long as the air conditioner is running. Why? Because they remove a lot of moisture per unit time. For instance, you can’t rely on natural evaporation to dry up a gallon or more of water every day. Yet, some remove as many as 20+ litres of water daily.

But this doesn’t mean that you should see water dripping from the exterior condensate drain pipe unless the primary pipe is overwhelmed or otherwise compromised.

How Much Water should Drain from Air Conditioner?

Generally, any water coming from the secondary/exterior condensate drain pipe is too much because the primary drain line is designed to handle all condensate drainage needs if all is well.

According to SFGate, many central air systems remove at least five gallons of moisture daily and the primary drain line handles it with no fuss. A larger sewer-connected drain line can even handle 20+ gallons of condensate per day.

So, if you see the water dripping from the exterior AC drain pipe, then either your AC is generating an excessive amount of water (you may want to know why) or not passing the normal drainage as the manufacturer/installer visualized (you also need to find out why).  

Why is AC Overflow Pipe Dripping

The following are the common reasons why your air conditioner’s exterior drain pump may (suddenly) drip lots of water and what to do about the situation.

1. Improper Installation

EPA states that more than 50% of air conditioning systems in the US are incorrectly installed. An incorrectly sized drain pipe, wrongly sloping primary drain line, and improper AC sizing can all lead to dripping exterior drains.

Solution: Make sure your air conditioning system is installed correctly by avoiding shortcuts and instead of hiring an expert for the job.

2. Clogged Drain Line

If your AC system is properly installed, then the first place to check if the exterior drain is dripping lots of water is the drain line itself. To be specific, is the primary drain blocked? Is it bent? If so, it may not smoothly drain the condensate into your sewer system.

Solution: Take measures to prevent drain line clogging. More importantly, regularly check the line for clogging and unclog it promptly.

3. Air leaks

 In a properly functioning AC system, air reaching the evaporator coils should go through the vents. However, air leaks can allow additional moisture into the AC, resulting in more condensate, potentially overwhelming the primary drain line.

Solution: Inspect your air conditioner vents to ensure you don’t have any air leaks and seal any leaks promptly.

4. Blocked/Filthy Air Filter

Blocked air filters/return air often leads to freezing at the evaporator and condenser coils because the coils depend on the warmth from return air to remain in a gaseous/liquid form. The melting frost/ice can cause lots of water in the AC.

Solution: Replace your filters at least every month or sooner as the manufacturer recommends or wash it as appropriate.  

5. Clogged Condensation Line

Just as a filthy/blocked air filter can cause AC freezing, so can dusty/blocked condenser coils. The latter of dirt/dust makes heat exchange impossible, leaving the coils colder and colder, eventually resulting in freezing.

Solution: Regular maintenance is the best solution here. Make it a habit to clean the AC, including the condenser and evaporator coils, regularly to prevent freezing.

6. Broken Pump

A few modern air conditioners use a built-in electric pump to drain the condensate lines. It’s especially effective in large ACs with built-in dehumidifiers that collect 20+ gallons of water daily. Thus, the drain pan may fill up, causing exterior drain leaks if the pump is broken.

Solution: Troubleshoot the pump to see whether it’s getting power and fix it appropriately. Loose wires and a dead motor are common issues here.

7. Other Reasons

Other reasons your exterior AC drains may suddenly begin to drip water include weather conditions, such as a particularly hot day and humid day, and other conditions that may result in freezing, such as dead or broken blower fans.

Solution: You can prevent many of these issues with an annual tune-up and regular maintenance. However, if the problem is already ongoing, call an HVAC technician immediately and let them help you diagnose and fix the underlying issue. 

Why your Drain Pan is Full of Water

If you notice that besides the dripping water, your drain pan is also full, the following are the most likely causes;

  • The drain line is clogged: If the primary drain line is blocked, condensate has nowhere to go. So, it will accumulate in the drain pan.  
  • The evaporator coil is dirty: Dirty evaporator coils often result in air conditioner freezing, causing excess water in the AC.
  • Incorrect AC installation: Finally, your drain pan may also fill quickly if the AC is poorly installed or incorrectly sized.

How to Maintain/Clean your AC to Prevent Water Leaks

The three main air conditioner parts you need to clean/maintain to prevent water leaks are the draining system, coils, and fan. Here’s how to clean each;

How to Clean AC Condensate Drain Line

To clean the drain system, shut down the air conditioning unit at the circuit breaker and unscrew the access panel to locate the drain pan.

The drain line is located at a saturation level under the evaporator coils. If water is overflowing in the pan, use a vacuum cleaner to get rid of the clog. Alternatively, use a suction pump.

We recommend working from outside the house for the best results.

Clean Air Conditioner Coils

You need to clean both the evaporator and condenser coils. Begin by turning off the appliance and unplugging it from power. Then remove the front cover and, using a vacuum cleaner, thoroughly clean the coils.

If you notice bent coils, call your ac repair service to straighten them as bent coils can impede the smooth flow of refrigerant.  You can also rinse the outdoor coils with water.

Clean the Fans

Finally, it’s easy to clean air conditioner fans. With the unit disconnected from the power outlet, remove the indoor chassis to access the fan. Then spray the fan with a suitable spray solution and let the solution settle for 15 minutes.

After that, rinse it with warm water and allow the water to drain and the fan to dry before out begin using the AC again.

Should My Exterior AC Drain Pipe Be Dripping Water FAQs

Can I still use my AC if it’s leaking water?

No, it would be best to stop using an AC that’s leaking water as you may aggravate the underlying problem. Consider shutting down the unit, troubleshooting it, and fixing the problem first.

Why is water dripping from my AC?

If water is dripping from your air conditioner, it’s most likely because of a blocked condensate drain line. However, it can also point to other issues such as dirty filters, dirty coils, and a frozen AC.

How do you clear an AC drip pipe?

To clean your drain line, mix one cup of bleach and one cup of water and pour the solution into the top of the condensate drain line. Then wait for 15 minutes and scrub gently into the pipe using a brush. After that, flush it with clean water.

How do I stop my air conditioner from leaking water?

The only solution is to fix the cause of the leak. This often means troubleshooting and unclogging the drain pipes. However, you may also need to take steps to prevent AC freezing.

How often should you clean an AC drain line?

We recommend cleaning your air conditioner drain lines every three months or sooner to prevent clogging. Wash it with a vinegar solution or warm water and allow it to dry.

How much does it cost to unclog an AC drain line?

Flushing a clogged drain line costs between $75 and $250. However, the costs are significantly higher if you also need to replace the damaged air conditioner parts.


The air conditioner’s exterior drainpipe, under normal circumstances, doesn’t drip water. however, it may begin dripping water if something is wrong.

If this happens, stop using the AC, get to the bottom of the matter, and fix the issue as quickly as possible.

Otherwise, you may be left with bigger and more expensive damages. If the water leak persists, call your HVAC technician.