Why Does My Portable AC Fill with Water Quickly?

Written by: Paul Cathro

Updated on: December 23, 2022

Technician checking portable AC unit

A portable air conditioner that fills with water quickly is usually nothing to worry about, although there are a few things to note. 

Portable air conditioners produce water when they pass warm air over a cold coil, which converts moisture in the air into a liquid. 

While this process is normal (you can expect a portable AC to produce between two and three pints of water per hour in moderate humidity), excess water can be annoying when the unit frequently pauses due to a full condensate tank. 

If your air conditioner is producing more water than usual, this can signal that the unit isn't working as it should, either because of a fault or incorrect settings. 

This article explains why portable air conditioners fill with water quickly to help you figure out what to do next. 

How Much Water is Too Much?

Air conditioners remove moisture from the air, so it’s normal for the water pan to fill up quickly in humid and wet environments.

Even emptying the pan every hour is normal for some brands depending on the pan's size, the cooling capacity, and relative humidity.

For example, a portable air conditioner can produce more than four pints of water per hour in an environment with 75% relative humidity.

In low-humidity environments, a portable air conditioner might produce only one pint of water per week!

Recognizing when a portable air conditioner produces too much water is easy – it’s when you are emptying the pan more often than normal. There are various reasons why this could happen, which we’ll run over below.

Reasons Why Portable Air Conditioners Fill with Water Quickly [And Fixes]

All portable air conditioners produce water because moisture evaporates and forms as water droplets when air condenses (cools) over the coil. As such, water collecting in the drainage tank signifies the unit is working. 

The amount of water that collects in the drainage pan depends mainly on the climate – higher humidity levels equal more water. 

In dry climates, the water that collects in the drainage pan is minimal because the exhaust vent is sufficient to expel nearly all the vapor.  

When humidity levels rise, portable air conditioners collect lots of water in their tanks as a natural by-product of removing moisture from the air. 

It's also possible for portable air conditioners to run inefficiently after periods of downtime and to develop faults in the pump, coil, and fan. 

6. High Humidity

High humidity increases a portable air conditioner's water production because it extracts more moisture from the air.

The critical consideration is the source of the humidity and whether you can do anything about it. 

We can split humidity sources into two categories:

  • Internal – activities like cooking and showering increase humidity levels in your home. You can isolate this humidity by keeping doors closed and using extractor fans to pull humid air out of your home at the source. 
  • External – the climate you live in mainly determines your home's humidity. People living in humid states like Alaska, Florida, and Louisiana must drain their portable AC tanks much more frequently than those in arid states. 

In high humidity, you can expect a portable air conditioner to collect more than four pints of water per hour. 

Humidity sources you can control include your kitchen and bathrooms by isolating them so that humid air does not enter your air conditioner. While you can't do anything about humidity outside your home, you can keep windows and doors closed and plug any gaps. 

Another option is a portable air conditioner with self-evaporative technology. These units vaporize moisture in the air and expel it through the exhaust pipe, eliminating (or reducing) the need to manually drain the condensate tank. 

5. It's Newly Installed or Used for the First Time in the Season

A new portable air conditioner usually meets a highly humid room, and the moisture in the air is more than it can ventilate outside. 

It is typical for a brand-new portable air conditioner to fill with water within eight hours on first use in a humid environment. The same scenario applies to portable air conditioners dragged out of the garage for the start of the hot season. 

The good news is that if you run your portable air conditioner on cycles, the water that collects in the drainage pan reduces over time because your portable AC is re-conditioning air it has already conditioned. 

To fix the issue, run your portable AC on a half-hourly cycle after the first hour so that it doesn’t have to condition humid air.  

Simply put, portable air conditioners collect less water the more they are used. Still, it's crucial to strike the right balance between running time and longevity because continuous running can cause premature component wear. 

4. The AC is Faulty

When we talk about AC faults rather than component faults, we mean issues with the evaporator coils or parts dealing with the condensate.

Evaporator faults can cause the water tank to fill up too quickly. The fault could be something as simple as a dirty evaporator coil or an electrical connector that has worked loose after moving the unit around. 

Coils usually get dirty when the air filter doesn't work, so a dirty air filter is a good sign that the evaporator needs cleaning. 

However, air filters don't catch all dirt, so grime will always build up on the coils. We recommend inspecting your portable AC coils every month and cleaning them with a soft-bristled brush and coil cleaning solution or white vinegar. 

At worst, you might have a faulty evaporator coil feeding excess water to the drainage tank rather than out of the exhaust. Other common symptoms of a faulty evaporative coil include the unit turning off and blowing warm air.

3. Faulty Condensate Pump

A condensate pump removes excess water from the air conditioning system, pumping it outside the system to a nearby drainage point. In theory, this stops water from collecting in the tank, eliminating the need to empty it. 

However, condensate pumps are prone to faults, especially when working continuously in very humid environments. 

When a condensate pump fails, water that would pump outside the system stays in the system, collecting in the water tank. 

Condensate pump faults usually manifest as a drop in performance, where less water is pumped away from the system. Over time, the pump chugs away but loses efficiency, with more water collecting in the tank. 

Try these steps to diagnose a faulty condensate pump:

  • Check that it's receiving power.
  • Turn it on and off; see if it boots up with water in the tank.
  • Place your portable AC in a humid room to see how much water the pump removes from the system (it should remove all of it). 
  • Inspect the float – if the float is stuck or damaged, this can trick the condensate pump into not working. 

The lifespan of a condensate pump is 2-3 years because they have mechanical parts prone to wear. They can suffer early failure if running continuously in extremely humid environments like wet spaces.

2. Broken Portable AC Blower Fan

Your portable air conditioner has a blower fan to whip cold air away from the evaporator coils and circulate it around your home.

If your portable AC blower runs too slowly, the coils can freeze and accumulate ice, causing excess water to drain into the pan when it melts. Because ice melts quickly, you'll notice the drainage pan filling with water when you turn the unit off.

It's crucial to note that airflow rates are affected by the fan motor – the electromechanical component that drives the blades. If the motor has damage, it will run at a reduced RPM, or not at all, depending on the fault.

Faults with electrical components like switch relays and control boards can also reduce the flow rate and performance of the fan motor.

If the blower fan whirrs, squeaks, or groans when operating, it could be something as simple as a loose screw or housing mount.

In any case, we recommend a professional diagnosis for safety reasons. Contact your portable AC manufacturer and retailer to see if they offer a repair service. If not, an air-con engineer or repair shop will be able to help.  

1. Plugged Drain Holes or Tubes

A clogged or plugged condensate tube will force excess water into the drainage tank and make it appear like the condensate pump isn't working. This can also cause leaks in the system with a small puddle under the unit. 

Plugged drain holes stop water from escaping the drainage tank, causing water to build up in the water pan. For example, if you feed water from the drain pan to a bucket, water will stay in the pan if the drain hole is blocked.  

Check all drain holes and tubes for blockages, dirt, and grime. Mold build-up in the condensate tube can also cause problems by holding excess moisture, which feeds the drainage pan with water after switching the unit off.

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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