Why is My Portable Air Conditioner Leaking Water?

Written by: Paul Cathro

Updated on: December 23, 2022

woman emptying water from AC

The only thing coming out of your portable air conditioner should be cool air. If it’s leaking water, this signifies that something is wrong. 

Water leaks usually have an innocent cause, like a blocked drainage hose, but they can also signify damage and worn components. 

Getting to the bottom of the leak will ensure your portable AC doesn’t have any electrification risks and continues working normally. 

This article covers the common reasons why portable air conditioners leak to help you figure out why you have a pool of water on the floor. 

The Different Ways a Portable Air Conditioner Drains Water

To identify a water leak we first need to look at the different ways a portable AC can drain water.

Once we've identified your particular type of air conditioner we can more quickly diagnose and fix the problem.

1. Using a Condensate Tank

With this drainage method, water from the evaporator coils flows into a condensate tank, also known as a drainage tank or pan.

The tank needs emptying manually, creating a pool of water on the floor if it spills over.  

This is the most common method of drainage and even most units that use the next two methods will still have a drainage pan as back up.

2. Using a Drainage Hose

A drainage hose connects to the condensate tank or drainage spout and moves water away from the system.

The drainage hose is usually fed to a sink or external drainage point, eliminating the need to empty a drainage pan. 

The hose is typically fed out of a window or into a sink.

3. By Evaporation

Every portable air conditioner evaporates some moisture in the air, but those with self-evaporating technology evaporate most of it.

This auto-drainage feature eliminates or reduces the requirement to empty the drainage pan. 

Only the more expensive models can drain by evaporation like this.

Portable AC with Condensate Tank is Leaking Water

If you've identified your AC as being one of those with a drip pan (the truth is most do) then these are the issues you need to be aware of.

Reason #1: The Drainage Pan is Cracked

A cracked drain pain will leak water like no tomorrow. The good news is that diagnosing a cracked drain pan is easy:

  • Turn off the portable AC.
  • Empty the tank. 
  • Turn the unit on
  • Set it to cool mode. 
  • Inspect the condensate pan for leaks. 

If there’s a leak, water will pool on the floor underneath the drainage pan, seeping around the edges of the unit.

Unfortunately, drainage pans are not usually replaceable, but a waterproof two-part resin filler might do the trick if there’s a crack on the exposed casing.

Ensure the unit reaches room temperature first so that the resin cures properly.

Reason #2: The Float Switch is Broken

The float switch tells your portable air conditioner when the condensate tank is full, making the unit switch off to stop it from overflowing. 

If the float switch malfunctions, water will trickle into the condensate tank indefinitely, and you will have a pool of water on the floor. 

Float switches are not user-replaceable, so your options besides replacing the entire unit are regularly emptying it yourself or installing a drain hose to remove water from the unit.

A drain hose goes into the drainage spout and works automatically. 

Portable AC with Drainage Hose is Leaking

For air conditioners with drainage hoses you should check on the following.

Reason #1: The Hose is Blocked or Broken

Drainage hoses can get blocked with a build-up of dirt and grime, especially when they cool down humid spaces like bathrooms and kitchens. 

Smoke from kitchens and steam from bathrooms can produce mold and slime inside the drainage hose, which dirt sticks to. Over time, the dirt builds up, creating a blockage.

The good news is you can remove a blockage with warm water and pressure – blow warm water through the hose to clear the obstruction and run bleach through the hose every few months to stop mold from forming.

If your drainage hose isn’t blocked, it could be broken. A snag can compromise the integrity of the plastic, causing a tear, or you might cut the hose by accident. 

Remove the hose from the unit and inspect it for damage. If there’s no visible damage, you should look at other possible leak sources. 

Reason #2: There’s a Leaky Connection

Check the connection between the drainage hose and drainage spout – if you can feel water/moisture, there’s a problem with the connection. 

The best way to assess the connection for leaks is with tissue paper – wrap some around the connection point and see if it soaks up any water. 

Reason #3: The Condensate Pump is Faulty 

A faulty condensate pump can leak water. The most common reason for leaks is clogging, where grime and mold build up inside the pump. With extensive use, it’s also possible for the motor that drives the pump to fail. 

The best way to test the condensate pump for leaks is to fill the tank with water and see if the pump does its job correctly. It has a problem if water leaks around the pump casing and connector.

Portable AC condensate pumps last around 2-3 years, so if your pump is older than this, it might be time to replace it anyway. 

Self-Evaporating Portable AC is Leaking

If your air conditioner is one of those that can self-evaporate the waste water then check on the following.

Reason #1: The Exhaust Hose isn’t Connected Properly 

The exhaust hose removes warm air and a significant percentage of the moisture from your room.

If it isn’t connected correctly, vapor in the hose can liquify and drip down, giving you a nice pool of water on the floor. 

Additionally, your portable AC won’t be able to evaporate enough water if it can’t expel enough air, making the condensate tank fill up. This can fill quickly in high humidity and overflow if there’s a problem with the float.

Reason 2: You Have a Loose Drainage Plug

If the plug on your drainage tank is loose, it won’t keep the unit watertight. Check the cap for any drips and tighten it as much as possible. 

If the cap is wet after tightening it, the O-ring/bung around the cap might have perished, so you could try replacing it.  

Drainage plugs can sometimes work loose when you move the unit around and are prone to movement when exposed to heat. After periods of high temperatures, check the plug to ensure it’s tight.

Problems Facing All Portable AC Types

  • Low refrigerant levels – if your portable air conditioner has low refrigerant, it can collect too much ice on its coils. When you switch the unit off, the ice melts, and the water can drip onto the floor. 
  • Dirty filtersdirty and clogged air filters can cause condensation build-up, dripping water down the unit onto the floor. The filter should not be wet – remove it and see if it has any moisture. If it does, clean it. Ensure the air filter is dry before switching your portable air conditioner on. 
  • Dirty drain lines – a drain line doesn’t need to be clogged to cause a leak. Even a mild obstruction like dirt and grime inside the line can change the water flow, forcing water to escape at the top of the connection point. Inspect the drain line to ensure it is clear of dirt, grime, and obstructions. 
  • Extreme environments – don’t expect your portable AC to cool down a steamy bathroom or kitchen without creating a pool of water. Condensation will form inside the unit and drip down no matter what you do, and it will also form on the outside of the unit, dripping onto the floor. 
  • Age – over time, portable air conditioners' electronic, mechanical, and static components wear down. Seals, clips, and connections are the usual culprits with leaks. Consider replacing your portable air conditioner if it’s over five years old and you have noticed a drop in performance. 


About the Author Paul Cathro

Paul is an ex-HVAC engineer with 5 years 'in the trade'.

He acquired tinyhousehugeideas.com in 2022 and aims to make it the internet's most comprehensive HVAC resource for small homes in the next few years.

You can learn more about Paul's story here.

Browse his published work on the website here.

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