8 Reasons Your AC Unit Is Leaking Water (and How to Fix It)
The Spruce / Tessa Cooper
An air conditioner unit leaking water in the house can damage the walls and flooring. Often, the cause is as simple as a clogged drain line or a dirty air filter—repairs you can do yourself.
Learn why your AC unit is leaking water and how to fix the problem.
Normal AC Leakage
An air conditioner removes moisture from the air and condenses it into water. So, it is normal for all types of air conditioners to leak some water, either outside or into a drain tank or pan.
Window-unit AC: Water will drip off the back of the unit and onto the ground.
Ductless mini-split AC: A drain tube extends to the exterior to drain water directly outside.
Central AC: Some water may pool near the condensing unit outside. Also, a drain tube extends a few inches out of the side of the house, and this will drip water.
Portable AC: Water will drip into the unit's onboard tank, or the unit may pump the water through a window or floor drain.
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Clogged Drain Line
The AC unit's drain line might be clogged. This prevents water from the unit's drain pan from flowing to the outdoors. The drain line may be clogged by mold or general dirt and debris.
Unclog the Drain Line
Call an HVAC technician to unclog the drain line. The technician will either snake the line or suck out the clog with a wet-dry vacuum, followed by the application of a liquid PVC pipe cleaner.
A DIYer can also snake out the drain line with an AC drain line cleaner. This hand-held $20 to $25 device has a brush at the end for scouring the inside of drain lines.
To suck out the clog, use a special attachment that you attach to a wet-dry vacuum on wet mode. Attach the vacuum to the exterior end of the pipe.
Debris in Base Pan
Debris and vegetation around the base pan may cause water to leak around the outdoor unit. Too much debris will prevent water from draining out of the base pan.
Clear Debris and Cut Vegetation
Look for debris that has accumulated around the outdoor unit's base pan. Also look for excess grass or weed growth.
Clean out the debris to expose the base pan's drain holes. Cut a minimum of 12 inches of clearance around the unit. Do not let cut vegetation settle around the unit. Sweep it away and dispose of it.
Unit Out of Slope
Improper slope is a common reason why your window air conditioner unit is leaking water. The unit is tilted indoors, not outdoors, sending condensed water inside the house.
Slope the Unit Correctly
Check the level: Check the slope of the unit from front to back. Place a bubble level on the top of the AC unit, on the exterior side of the window (if accessible). The back of the unit should be about half an inch lower than the front.
Remove the AC: With an assistant holding the AC, open the window and slide the AC into the house.
Adjust bracket: Adjust the bracket that holds the unit against the house. Adjust it down one notch or turn the screw.
Install the AC: Install the AC unit and recheck its slope.
Faulty Condensate Pump
The condensate pump may not be working or may be partially working. The condensate pump is designed to remove condensed water from the AC's evaporative coil automatically. Without a pump to move the water, it will overflow the condensate tank.
Repair or Replace the Condensate Pump
Check electrical: If the condensate pump is plugged into an outlet (rather than hardwired into the AC unit), ensure the plug is still in place and the circuit breaker is flipped to ON.
Test the float: Check the float within the condensate tank. It should turn on when there is around 2-1/4-inch of water and turn off when the level reaches 1-1/4-inch.
Replace the pump: If you can't fix the condensate pump, replace it. Condensate pumps cost $50 to $100 and can be replaced by a DIYer with basic electrical experience. The pump will either need to be hardwired to the AC unit or wired to a cord that plugs into the wall.
Frozen Evaporator Coil
When refrigerant leaks, it can cause ice to build up on the evaporator coil. Located in the house, in the AC unit's air handlers, the evaporator coil absorbs heat and moisture from the house's inside air. If ice forms on the coil, it leaks water when it begins to thaw.
Fix the Refrigerant Leak
Open the air handler to check the evaporator coil. Clean the air conditioner coil. Cleaning will not fix the problem if there is a refrigerant leak. This should only be repaired by an HVAC technician.
Dirty Filter
A dirty AC filter blows dirt or insufficient air over the evaporator coil. This causes the evaporator coil to become too cold, eventually freezing, because less warm air flows over the coil.
Replace or Clean the AC Filter
Depending on the type of AC filter—either a disposable paper or washable mesh—either replace or clean the AC filter. Cleaning or replacing the filter is an on-going HVAC maintenance task.
Tip
The best air filter for evaporator coil issues is one that has a maximum airflow rating while still trapping dust and allergens.
Low Refrigerant
When an AC is low on refrigerant, it will not properly cool the evaporator coil, which can result in leaks. Even if the AC isn't actively leaking refrigerant as a result of damage, ACs will slowly lose refrigerant over time.
Recharge the Refrigerant
Call an HVAC technician to recharge the AC's refrigerant. The technician can match the refrigerant with the AC and charge it to its correct pressure.
Cracked Drain Pan
The drain pan that collects water from the evaporator coil may eventually crack or become rusted, causing water to leak into the house.
Replace the Drain Pan
While fixing cracks in an AC drain pan is possible, it's usually best to replace the entire pan. Depending on your AC model, drain pans cost from $50 to $150. With a new drain pan, you can be assured that the pan won't leak for many years to come.
Frequently Asked Questions
Should I turn my AC off if it's leaking?
You should turn your AC off if it's leaking. Turning off the AC stops the cause behind the leak, but it may take several minutes or even an hour or two for the leak to stop completely. After that, assess why your AC unit is leaking water. A clogged drain line, an incorrectly sloped unit, or a faulty condensate pump are common causes of a leaky AC.
Is it normal for an indoor AC unit to be dripping water?
An indoor AC unit should not be dripping water outside of the unit. Any type of indoor AC unit—a mini-split, a window AC, or a portable AC—condenses water from the air. Split air and window ACs drip water to the exterior. A portable AC collects water in an onboard tank, and this tank occasionally needs to be emptied.
Read the original article on The Spruce.
