No Water Coming Out of AC Drain Pipe? Why And How To Fix

Using the air conditioner is straightforward when everything is working as envisioned. Part of the service has to do is switch on the AC, set the timer, and wait for the appliance to keep your home cool and comfy round the clock.

Unfortunately, any minor mishaps can cause significant confusion, especially if you don’t fully understand how the AC works. One such issue is when the AC is not draining water. Should an AC drip water in the first place? And if so, when should it be dripping water? And can you fix the issue yourself?

We answer these and many other questions surrounding drain systems below, focusing on common reasons why an air conditioning unit may stop draining water and what you can do about it. Let’s jump right in.

Why is Water not Coming Out of my AC Drain Pipe and What Can I Do About It?

The first thing you should check when your air conditioner isn’t draining water is whether your drainage lines are blocked. A clogged drain pipe is the most common cause of standing water in the drain pan.

Although the finer details vary, all air conditioners have a drain system to lead water out of the AC unit. Some even have two separate systems that increase efficiency.

no water coming out of ac drain pipe

Why Do Air Conditioners Drain Water?

Air conditioners drain water because they naturally condense the moisture in indoor air. It’s a natural part of the air conditioning process, and one of the main reasons it’s called “air conditioning” rather than “air cooling.”

So, how does it happen? It’s straightforward. The air conditioner works by drawing hot, humid indoor moisture into the conditioning system via the return vents and passing it over the cold refrigerant-filled evaporator coils, allowing the refrigerant to absorb/extract as much heat as possible from the hot air.

The process cools down and loses some of its humidity. Then the now-warm refrigerant air flows back into the condensing unit for cooling. The evaporator coil provides enough surface area for heat transfer.

This humidity is left behind in the form of condensation on the coils. The condensation drips off into the drain pan and exits the HVAC system through the drainage line.

Unfortunately, water isn’t the only thing that’s often left behind on the evaporator coil. The air that blows over these coils can leave behind dust and dirt as well. If the dirt drips off in the water, it can move down the draining system and ultimately cause a clog.

The blower fan then forces the now-cool air out of the air conditioner and helps circulate it into your home. However, don’t forget that summer air is very moist because of high relative humidity. The hotter the weather, the more humid the air.

A house may also get the humidity down, the latex paint lets off a lot of moisture in order to dry, combine that with plaster/drywall hence a new house may need a lot of drying out to do.

So, as the return air flows slowly over the very cold condenser coils, condensation is inevitable. The higher the relative humidity, the greater the condensation.

Where Does the Condensate Go?

If you’ve seen clear water dripping from your air conditioner into the drip pan, that’s part of the condensate. The condensate line should be on the lower side of the pan so that water flows toward it and drip on the pan.

However, you may also not see it depending on the drainage mechanism the air conditioning system adopts. AC drain systems vary depending on many factors, including the size of the HVAC, how much water it produces, and installation location.

Generally, smaller units collect the little condensate in a tiny drain pan located inside the air conditioner and it naturally evaporates because of the continuous airflow thanks to the fan.

A mid-sized air conditioner that produces a few pints of water per day has a dedicated drain system sticking from the wall to drain this water into the soil next to the wall. So, you may see the water dripping throughout the day on very hot days.

Finally, large HVAC systems that produce gallons of condensate per day typically have two drain lines. The primary drain pipe connects to the property’s sewer line where it drains all the water, often up to 20+ gallons per day.

The secondary drain pipe sticks out through the wall and serves as an emergency drainage solution if the primary condensate drain line is blocked or otherwise compromised.

When Do Air Conditioners Drain Water?

As you can tell from the above explanation, different air conditioners drain water at different times and others may not even be dripping water at all.

That said though, an air conditioner will most likely be dripping water under the following conditions;

  1. It’s extremely hot outside: You will likely see water running through the drain pipe if it’s very hot outside because hot weather is associated with high humidity levels. The hotter the weather, the higher the humidity/condensation rate.
  2. It’s very hot inside your home: Your home may occasionally become extremely hot even when outdoor weather isn’t very hot for several reasons. For instance, whenever you do a lot of cooking inside the house in the summer, prepare to feel the heat. You’ll notice increased condensate drain these days.
  3. The air conditioner is in distress: An excellent example here is if your air filters are blocked. Blocked air filters often lead to freezing which can result in excessive water from the Ac as the ice thaws.   

Why You Should be Worried if Your AC Isn’t Draining Water

You should be very worried if you find out that your air conditioner isn’t draining water. The following are a few reasons why;

  1. Risk of water damage: The drain pan will fill faster than you can imagine. Then it may overflow, causing preventable and costly water damage. This water can damage your ceiling or even weaken the home’s structure over time.
  2. Risk of AC damage: However, before it damages your home, water inside the AC is very bad for the electrical component. It can easily cause short-circuiting and damage the control board and its components.
  3. Air conditioning may stop: Most ACs have a float switch (also popular as a wet switch or overflow switch) that cuts the aircon power supply when the drain pan is full to prevent water damage and electronic short-circuiting. So, the air conditioning will stop until you empty the pan.
  4. Risk of mold and other fungi: If water leaks into your insulation or caused mildew or sheetrock damage, it is best to call a professional company because it can enhance the growth of mold which can harm your health. It’s very difficult to escape mold infestation if you let standing water in the drain pan sit for several days.

Why is your AC not Draining Water?

The most pressing concern for homeowners is that the drip pan will overflow, causing water damage.

The main reason your air conditioner’s drain pipe, including the one that leads to the sewer line, may stop draining into the drain pan is because of a clogged condensate drain, though a failed pump and wrong installation are also common causes.

no water coming out of ac drain pipe

#1: Clogged Drain Line

Most AC units have a U-shaped trap in the condensate line. After a period of time, the trap clogs thus backing up the water into the condensate tray. This is the most common reason ACs stop draining water. Here’s everything you need to know about a clogged system

What’s a Drain Line?

An air conditioning drainage line is a piping system (PVC or metallic) that runs from the air conditioning unit outside the house to drain condensate collected in the AC.

Where’s the AC Drain Line?

The most visible part of the drainage line is a white PVC or copper pipe located near the outdoor unit. It is where the exterior pipe ends. However, you can also check near your indoor unit for a vertical PVS pipe with a cap on it. This is the access point for the condensate drain.

What Causes Drain pipes to Clog?

These lines can clog for many reasons. The main reason is, of course, dirt and debris accumulation. Hairs, pet dander, soils, and dust that enter the AC via return air may also find a way into the drain pipes, clogging them. Another common cause is the growth of algae in the pipes during the warm, moist monsoon season owing to poor maintenance.

Sign of a Clogged Draining Line

The most common signs of a clogged aircon draining system are standing water near the outdoor unit, water damage around the indoor unit, and AC system shutdown. If you see all three signs at a go, you almost certainly have a clogged AC system. A musty smell from the registers is also common.

How to Unclog a Clogged AC Draining Line

When the condensate line is completely blocked you could see distressing signs of water leaks in your home. Unclogging a blocked AC condensate line isn’t a complicated process, though you need a few handyman skills. Wear your hand gloves and proceed as follows;

1.       Turn off the AC at the circuit breaker

2.       Locate the drain pipe and identify the white cap

3.       Pull out the white cap with your hands

4.       Peek inside the pipe to gauge the extent of the clogging. Use a flashlight if necessary.

5.       Remove visible debris, especially the large pieces. Be careful not to push it further down.

6.       Pour one cup of distilled vinegar into the pipe, and let it settle for 30 minutes

7.       Use a wet/dry vacuum to pull out the items clogging the pipe

8.       Rinse with clean water and allow the pipe to dry

9.       Replace the drain cap

 After the clogged drain clears, you should be able to pour water into the pipe and it should immediately flow out.

If your air conditioner unit is still not draining correctly, you should contact HVAC repair technicians dealing in cooling, heating, plumbing, and air conditioning services.

#2: Failed Drain Pump

Most large ACs especially models with built-in dehumidifiers that remove several gallons of water per day, use drain pumps to drain the condensate. Thus, the draining process can stop if the pipe fails.

Solution: Loose wires, short-circuiting, blocked service valve and a dead motor are some of the reasons an AC drain pump may fail. The only solution is to repair the pump or replace it.

You’ll likely need the input of an experienced HVAC technician to replace the leaking service valve and other electrical appliances.

#3: Poor Installation

Aircon drain systems can only remove water smoothly if the installation is correct. Otherwise, the risk of clogging is very high or the unit may fail to drain altogether. For instance, the selection of the drain location is critical as is the slope.

A poor slope means the unit may not remove condensate water through gravity. Wrong draining pipe sizing is another potential stumbling block. The third AC unit of the house has water in the drip pan and this water is running out at the end of the pipe that is near the eave of the roof.

Solution: The only cure for poor air conditioner system installation is a professional installation. Don’t do it yourself if you haven’t handled AC installation or repair projects before.

Similarly, don’t cut corners by choosing poor small pipes or cheap pipes it can cost you more. Call a professional technician to conduct the repair services to your heating, cooling, and plumbing needs.

What to Do When Your AC Isn’t Draining Water

Whether the AC is blocked, poorly installed, or the drain pump has failed, there are a few basic service steps you must follow to stop the damage.

Turn off the AC:

Continuing to use an AC with a compromised draining line can further damage the air conditioner.

Clean up the water:

If you notice water pooling around the outdoor unit or water damage around the indoor air handler, clean it up.

Fix the drain line:

Check whether the drainage line is blocked. If so, pour a one-part water one part white vinegar solution into the pipe, let it soak for 30 minutes, and pull out the dirt with a wet vacuum.

Fix any other issues:

Make sure the HVAC system is properly installed, with the correct slope and right size drainage line. Also, ensure the drain pump (where applicable works properly).

Call an HVAC technician if you’re unable to fix some of the cooling, heating, or plumbing issues, especially rectifying installation mistakes, repair, and other maintenance services.


How much water should drain from an air conditioner?

Central air systems (heating, ventilation, plumbing, and air conditioning) generally drain 5-20 gallons of condensate water every day. However, smaller units, including portable ACs and window units drain several pints per day.

What happens if your AC draining line is clogged?

If your AC draining line is blocked, the condensate that your air conditioner has nowhere to go. So, the drain pan will overflow, and there’s also an increased risk of AC damage due to short-circuiting.

Is bleach or vinegar better for AC draining line?

Vinegar is the better of the two options. Using bleach on your AC often leaves residual bleach that can damage the drain pan and pipes. Using vinegar for preventive maintenance cleans the drain system without damaging the condensate pan and lines

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

It costs $75 to $225 to unclog a blocked AC drain line. However, the costs of these services can go up if you need to replace damaged parts of the system or the air conditioner, such as a compromised evaporator coil.

Can I use Drano in my AC drain line?

No, you shouldn’t. Drano is designed for food and grease, so it won’t work in your Ac pipes. Instead, use bleach or vinegar. Bleach is stronger, but vinegar is more friendly to the AC parts.


Now you know why ACs drip water, how much water a standard air conditioner drains, and the potential risks whenever your AC stops drip water. Most importantly, you know common reasons why an AC may stop draining water and how to fix the issues.

Give us or your technicians a call if you have any questions, need repairs, or for maintenance service on any cooling, heating, or plumbing problems.