Walking out to find a puddle under your air conditioner or noticing a damp spot near the indoor unit is unsettling, especially during a stretch of warm weather when you cannot afford for the system to be down. At Stan’s Heating, Inc, we get calls about water leaks throughout the cooling season, and the cause is rarely as serious as it first appears. That said, some leaks point to issues that need professional attention before they damage your home or equipment.
The short answer is almost always one of a small handful of culprits, and several of them you can check yourself before reaching for the phone. Below, we explain how an AC produces water in the first place, the most common reasons that water ends up in the wrong place, and the difference between a quick DIY check and a problem that calls for a technician.
Why ACs Produce Water in the First Place
Your air conditioner does not generate water; it removes it. Warm, humid air from your home passes over the cold evaporator coil, where moisture in the air condenses on the coil’s surface, similar to the way a cold glass of water collects droplets on a humid afternoon. That condensation drips into a collection pan beneath the coil, then flows out of the home through a condensate drain line.
When everything is working as designed, you may never notice this process at all. Water leaves the system through the drain, and the air coming out of the supply registers feels cooler and drier. A leak means water is not following its intended path, either because something is blocking it, the path is damaged, or the unit is producing more condensation than the system can handle.
Common Reasons Your AC Is Leaking
Most water leaks fall into one of the following categories:
- Clogged condensate drain line: Algae, dust, and biological growth build up inside the drain line over time and block the flow. When the drain backs up, water overflows the pan and ends up on the floor or surrounding structure. This is the most common cause of an indoor leak.
- Dirty evaporator coil: A coil coated in dust and debris does not release water from its surface efficiently. Water can run off in unexpected directions and drip outside the collection pan rather than into it.
- Frozen coil from low refrigerant or restricted airflow: When the coil freezes and then thaws, the volume of melt water can overwhelm the drain pan. Low refrigerant or a clogged filter are the most common reasons a coil freezes.
- Damaged or disconnected drain pan: Drain pans are typically plastic or metal, and over years of service they can crack, rust through, or shift out of position. A pan that no longer holds water leaks the moment the system runs.
- Improperly installed or unlevel unit: An AC that is not level cannot drain correctly. This is more common after a recent installation, after settling has shifted the unit, or after a service call where the unit was moved.
Quick Checks Before Calling a Tech
Before you assume the leak is a serious problem, walk through a few safe checks at the unit. None of these involve opening sealed components or working with refrigerant.
Start by turning the system off at the thermostat and giving it 30 minutes to settle. Check the air filter; if it is dirty or clogged, replace it before doing anything else, since restricted airflow is one of the most common reasons coils freeze and overflow. Look at the indoor unit and the drain pan beneath it. If you can see standing water in the pan but no flow into the drain line, the line is likely clogged. Some homeowners clear minor clogs by attaching a wet/dry vacuum to the outdoor end of the condensate line for a few minutes. It is also worth confirming the thermostat setpoint is reasonable, since running the system unusually low on a humid day can produce more condensation than the drain can handle.
When a Leak Means a Bigger Problem
Some leaks signal issues that you should not run the system through. If you see ice on the refrigerant lines or evaporator coil, shut the system off and let it thaw completely before turning it back on. Continuing to run a frozen system can cause compressor damage, which is one of the most expensive repairs in residential HVAC.
Suspected refrigerant leaks are another stop-and-call situation. Refrigerant is not consumed during normal operation, so a system that is low on refrigerant has a leak somewhere in the lines, the coil, or a fitting. Topping off without finding the leak is a temporary fix at best. If your system is leaking water and also struggling to cool the home, our AC repair team can pinpoint the cause and get the system back to running properly.
Preventing AC Leaks With Maintenance
Most water leaks are preventable. A professional HVAC maintenance visit at the start of cooling season catches the conditions that lead to leaks before they become problems: the coil gets cleaned, the drain pan gets inspected, the condensate line gets flushed, the refrigerant charge gets verified, and airflow gets measured. Most of those tasks are difficult to do well from the homeowner’s side of the access panel.
Joining our Maintenance Club covers seasonal tune-ups for both your heating and cooling equipment, and members get priority scheduling when something does go wrong. For a system that runs hard during the eastern Oregon and western Idaho summers, that combination tends to pay for itself.
Frequently Asked Questions
AC Leaking Water? Stan’s Heating, Inc Can Help — Call or Schedule Online Today
A water leak is one of those problems that tends to get worse the longer it runs. If you have ruled out the easy fixes and the leak is still there, our team is ready to help. We diagnose and resolve cooling issues across Ontario, OR and the surrounding service area, from minor drain line clogs to full coil and refrigerant repairs.
Contact us today to schedule service and get your AC back to drying air, not dripping it.
