What Causes the Running Water Sound in Your Air Conditioner?

May 16, 2025

Running water is one of the most soothing sounds in nature. However, this is also one of the last noises you want to hear coming from your HVAC unit. While it’s normal for air conditioners to make faint humming noises during operation, rushing water sounds can indicate malfunction or defects. A look at the major causes of water noises inside your air conditioner can provide guidance on how to seek professional help to resolve the issue.

Clogged Condensate Line or Drain Pan

Clogged condensate lines can easily produce the sound of rushing water. As part of the operating cycle, your AC unit pulls warm air out of the room and eventually disperses it outside. When the warm air blows over the evaporator coils, it cools down and produces moisture or condensation as a result. The condensate line then drains this moisture buildup into a collection area known as the drain pan. If the condensate line is defective or clogged, the accumulation of moisture can create a running water sound. Similarly, a drain pan that gets too full can begin overflowing and produce running water noises. A professional can inspect and repair the condensate drain line to prevent water damage to your property.

Frozen Evaporator Coils

Frozen evaporator coils can cause multiple problems within your AC unit. The purpose of the evaporator coil is to hold the refrigerant and to help absorb heat from warm air within the home. Without proper maintenance, however, evaporator coils can accumulate dirt, grime, grease, or debris. This causes the restriction of airflow and can result in the development of ice on your evaporator coils.

As the ice melts due to heat fluctuations, you may begin to hear trickling or a running water sound. Regular inspections and maintenance from professionals can help prevent ice from building up on coils. Since handling evaporator coils requires training, you should never attempt to scrape or defrost them yourself. Experienced HVAC technicians have the equipment necessary to remove ice and frost from these delicate components without damaging the unit.

Dirty Air Filter

While it may seem unrelated to everyday AC cycles, a dirty air filter can eventually result in water sounds coming from the unit. The filter helps prevent airborne dust and debris from clogging the unit’s interior. But when your air filter is too dirty, these unwanted particles can begin to accumulate on interior components and restrict airflow. For example, a dirty air filter may be the underlying cause of that pesky buildup on your evaporator or condensate coils.

When these coils malfunction and condensation forms in the unit, you will then hear the water sounds. To avoid this, experts recommend changing the air filter at least once every 90 days. You can also speak with an HVAC professional about the feasibility of adding a high-efficiency particulate air (HEPA) filter to remove small particles like mold or pollen. An HVAC professional can also help you choose a filter with the correct size and minimum-efficiency reporting value (MERV) rating for your air conditioner model.

Low Refrigerant Levels

Low refrigerant levels can also create a running water sound. Inadequate refrigerant levels often result from leaks or an undercharged system. Without sufficient refrigerant, the evaporator coil will fail to absorb any heat that moves through the AC unit. This forces your air conditioner to work harder to complete each cycle, eventually resulting in excess condensation that produces running water sounds. Replacing refrigerant is a complex process that involves safe handling of potentially harmful chemicals, so it’s important to reach out to a professional to refill low refrigerant.

Broken Thermostat

A broken thermostat or poor temperature calibration can cause AC cycles to run for longer periods than necessary. Not only does this excess work shorten the lifespan of your unit, but the continuously cold temperatures can cause the evaporator coils to freeze over. This leads to the buildup of condensation and can result in that dreaded running water sound.

Other signs of a broken thermostat include inconsistent room temperatures, erratic unit behavior or short cycling, or indoor temperatures that fall more than 10 degrees outside of the established settings. Fortunately, an HVAC professional can determine whether it is feasible to repair or replace the thermostat without needing to replace the entire AC unit. You may also consider upgrading to a smart thermostat that can efficiently regulate temperatures and help save on energy costs.

Broken AC Blower

The AC blower is a device that helps move air along the coils within the unit. This device plays an essential role during the heat-transfer process. If the blower is defective or operating at a low speed, the coils may start to freeze. Once any ice thaws and melts, you may start to hear a running water sound. Fixing the blower or motor is definitely a job for the professionals. So you should always schedule an appointment with an HVAC company if you suspect a lack of airflow within the unit.

Improper Installation

If you hear running water from a recently purchased unit, it’s possible that you might have an installation error on your hands. For example, an air conditioner that has not undergone proper leveling will not be able to drain condensation correctly. This can cause a lot of moisture to pool beneath the unit and create the running water noise. Reach out to a technician to correct the issue or check for underlying manufacturer defects.

Other Common Water Sounds

What if you are unsure if your AC noise constitutes a “running water” sound? There are several other noises that can escalate into a running water sound and can all indicate possible issues with your AC unit. These sounds include dripping, bubbling, gurgling, or hissing.

Dripping Sounds

Many homeowners report that water sounds often start with dripping. The good news is that occasional dripping is often part of the normal dehumidifying process as condensed water falls into the drain pan. This periodic noise can signify that your unit is still working properly. If the dripping noise becomes too frequent or persistent, however, it may indicate a clogged condensate line or full drain pan. While some air conditioners have a float switch that automatically turns off the unit before the drain pan overflows, this float switch can easily wear out or malfunction. Routine maintenance can help check these components to ensure proper operation of your appliance.

Gurgling Sounds

Gurgling sounds are often more worrisome than dripping sounds. A gurgling noise can indicate insufficient refrigerant that has caused low pressure within the evaporator coils. The gurgling noise can also signify a bubble within the refrigerant line. Finally, this sound may also result from overcharged refrigerant. It is important to have a professional look into any gurgling noises to rule out accidental exposure to refrigerant. According to the Environmental Protection Agency, domestic refrigerant exposure is a toxin and biological health hazard. A technician can bring the right protective gear to minimize the risk of exposure to your household.

Contact Us Today

Hearing running water noises in your air conditioner may seem scary at first, but the situation does not have to feel hopeless. [company_name] provides AC services for homes in San Antonio and surrounding areas. We conduct air conditioner inspections and efficiently complete repairs. Our San Antonio HAVC technicians can also install air conditioner upgrades and smart thermostats. In addition to air conditioners, we can also install humidifiers and ductless mini-splits. We offer cost-saving maintenance agreements as well as 24/7 emergency services for air conditioner problems that simply cannot wait. Contact [company_name] today for all your HVAC needs.

1 Comment

  1. Anonymous

    The running water sound is the pump circulating the refrigerant around the system. You hear this because you have turned your ac off but you have the fan portion still running and the pump portion of the ac is still circulating refrigerant. If you turn off the ac completely including the fan, the water noise should stop.

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