Why Is Water Leaking From My Air Conditioning Unit?

Water leaking or dripping inside your house from your AC unit is a common problem. But where does this water come from?

Water condensation is an occurrence of the refrigeration cycle. Warm, humid air is pulled across a cold evaporator coil in the air handler.

As the airflow comes in contact with the cold coil, it condensates because it is below the dew point.

Have you ever taken a cold beverage out of the refrigerator and placed it on the counter. Water condensates on the bottle - same principal.

Here are the five most common reasons your AC is leaking water:

1. Condensate drain line clogged

2. The air filter is dirty

3. The evaporator coil is dirty

4. Low Refrigerant/Freon level

5. Primary drain pan rusted or cracked

Now for a little more detail of each problem, why it happens, and how to resolve the issue.

1. Condensate drain line clogged.

The condensate drain line (usually 3/4" PVC) attaches to the internal drain pan of the air handler. Water then flows outside via gravity.

In some situations, the drain line from the unit drains into a condensate pump. Once the water reaches a certain level in the pump, the pump cycles on and pumps the water outside.

Algae grow's inside of the drain line (and condensate pump) if not maintained. With the drain line restricted, water overflows at the air handler or pump.

How do you fix it?

Unless the drain line is severely clogged, this is an easy fix. Find where the pipe exits your house. Remember you're looking for a 3/4" white PVC line.

Grab your wet/dry vacuum, place the hose on the end of the drain line (try to get the best seal you can) and suck out the line.

Another technique if you do not have a vacuum, is to use water. This method requires you to be more careful.

Take your water hose and blast water up the drain line for 1 to 2 seconds and take the hose off.

Remember, the drain line goes all the way back to the air handler in your house.

Be careful if too much water is used, it can overflow into your house. Please use caution.

If you have a condensate pump, we recommend you call a professional.

There may be some additional control wiring to disassemble and some high voltage that could be hazardous. We are just trying to unclog your drain. Not kill you.

If Air Zero clears your drain, we often use high-pressure nitrogen or a particular machine designed to suction out the drain line. In some cases, the sediment in the line solidifies, and the drain line will need to be replaced.

2. Air Filter is dirty

Why does a dirty air filter cause a water leak? HVAC systems are designed to move a certain amount of air across the evaporator coil.

When the air filter is dirty, it slows the volume and the velocity of air through the air handler.

If this happens, the refrigerant in the system doesn't absorb the amount of heat from the air the system is designed for.

Because of this, the temperature of the refrigerant circulating in the evaporator is literally below freezing - 32 degrees- the freezing point of water.

The humidity (moisture) in the air starts to freeze on the evaporator coil. As ice forms, it has a snowball effect in that it causes, even more, restriction of airflow thus more ice accumulation.

When the AC system shuts down or is turned off - the ice melts and drips off the face of the evaporator.

There is no mechanism to capture this water. So now you have water dripping on your floor or through your ceiling- Not good.

How do you fix it?

Keeping up with regular air filter changes is the simplest thing a homeowner can do to help keep their equipment clean.

Changing the filter regularly also keeps the efficiency of the A/C equipment at its peak.

Please note: the MERV rating (Minimum Efficiency Reporting Value) determines how efficient your air filter is at filtering dirt.

The more often you will likely need to change your filters.

A better filter does a better job & gets dirtier faster. We recommend changing your filter monthly.

3. The evaporator coil is dirty

A dirty evaporator coil means you haven't changed your air filter frequently enough or maybe you didn't have a filter. This is HVAC suicide.

Now, all the dirt that the filter is designed to catch will be embedded in the evaporator coil. The evaporator coil is a heat exchanger. Air passes through the coil; the refrigerant absorbs the heat out of the air.

Now imagine there is a blanket (DIRT) over the evaporator coil - not very efficient.

For the same reasons listed above with a dirty air filter, ice will form.

How do you fix it?

You will likely need professional help.

We remove the evaporator coil from the air handler and chemically clean.

Cleaning restores factory new condition. Once it's clean, the efficiency of the system is dramatically improved.

Now keep up with your filter changes.

4. Low Refrigerant / Freon Levels

Low refrigerant levels also mean lower system pressures in the AC system. The lower the system pressure, the lower the temperature of the refrigerant in the evaporator coil.

If the pressure is too low, ice can form on the evaporator coil. Similar to the above dirty filter problem.

How do you fix it?

Low refrigerant levels mean you have a freon leak in your air conditioning system. Coolant leaks are detrimental for many reasons.

Have a professional repair the leak and recharge system to optimal levels.

5. Primary drain pan rusted or cracked

Years ago HVAC manufacturers produced residential air handlers that had metal drain pans. Guess what? Metal rusts.

These pans rust through or the rust flakes off and clog the drain line. Newer AC units have plastic drain pans. This is an improvement but can crack, usually around the thread where the drain line is attached.

How do you Fix?

If your system has a metal primary drain pan, you’re likely in the market for a new AC system. Plastic drain pans can be replaced or sometimes patched with epoxy.

AC Water Leaks Can Be Very Damaging

Many times we have seen the damage water leaking from an A/C system can do to a house. From damaged wood flooring to mold growth. Ceilings that have fallen & damage to the property below you if you live in a condo or multi-story house.

Your HVAC system should have at least one safety condensate overflow switch. This safety mechanism is designed to shut the unit off if excess water is not draining.

A secondary safety drain pan should also be installed with a redundant safety switch as well if your air handler is horizontal above a living space. Secondary drain pans are required by code.

We also install secondary pans on air handlers that are installed vertically in multi-story properties. Although this is not required by law, we have seen too many times the damage water can cause without this added safety measure.

Need Professional Help?

Most of the problems listed above are avoidable with regular air conditioning system maintenance. We confirm you have a safety float switch and that it is functioning correctly & check for any indication of water leaks.

Air Zero provides award-winning service to Largo Fl, and surrounding areas like St. Petersburg, Seminole, Clearwater, and all of Pinellas County.

If you have any questions, please give us a call at 727-392-6111.