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Evaporator Coil Leak: What You Need to Do

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During the hot days of Summer your air conditioner can be your best friend, but when you have an evaporator coil leak the cold air it normally blows can turn warm. Leaving you in an uncomfortable house with the need to fix the situation as soon as possible.

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This article will help you identify if your evaporator coil is leaking, and if it is, what you need to do. We'll also help you determine when it's time to call an HVAC professional so you can get the cool air flowing again.

What is an Evaporator Coil?

All air conditioning units have what's called an evaporator. The evaporator is what houses the refrigerant in its liquid state; and the refrigerant circulates through the evaporator core and coils. 

As the warm air passes over the coils, the refregerant collects the heat from the air and leaves the air cool. The A/C unit discharges the warm air to the exterior of the house and pumps the remaining cool air inside the house.

When an A/C evaporator coil leaks, the refrigerant escapes and becomes an environmental hazard. This causes the air conditioner's cooling efficiency to decline and your unit will need to work harder in it's attempt to provide you with cool air.

Many homeowners order a refrigerant recharge instead of finding and fixing the source of the problem. However, this not only can get expensive, but you'll simply be spending money to patch an issue which you'll need to address again in the future.

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What Causes a Leaking Evaporator Coil 

A/C evaporator coil leaks are possible on new units if the system wasn't installed correctly or there was a manufacturing defect. Although rare, it is usually noticable within a couple of months and can be repaired by re-soldering joints or tightening fittings.

By far, the majority of evaporator coil leaks occur after the unit has been in operation for at least several years. The most common causes are as follows:

Formic Acid Build-up - When copper, water and oxygen are present they develop a reaction called formic acid. This is a common problem since all three of these substances are present within the evaporator coil. Over time, the build-up of formic acid begins to eat it's way through the copper tubing.

Modern Coil Design - Many A/C units are built with thinner copper coils than the older models. This is especially common in high-efficiency A/C units where manufacturers are working hard to improve the heat transfer between the refrigerant and the air it's trying to cool outside the coil. The thinner copper tubing may be more efficient, but it'll also corrode and develop a leak quicker than the thicker copper tubing.

Refrigerant Type - In January of 2010 the government required manufacturers to stop using R-22 refrigerant in new models. The more environmentally friendly refrigerant, R-410A requires greater internal pressure to maintain efficiency. The higher operating pressures combined with thinner copper coil walls, makes it easier for corrosion to penetrate and cause a leak.

Signs of an Evaporator Coil Leak

If your Evaporator coil is leaking you might see black or blue-gray deposits on the coils or joints, but there are also a few telltale signs you may notice in everyday life:

  • Vents not blowing cool air - If you notice that your registers aren't blowing cold air (or the air isn't as cold as it should be) when the air conditioner is working, it could mean your evaporator coil is leaking. 
  • Increased Utility Bills - If you notice that your utility bills are higher than normal it could be that your A/C system is working harder than usual in the attempt to get cooler air.
  • Reduced Cooling - If you have a leak in your evaporator coil you may notice that it takes more time for your AC system to cool your home. Since refrigerant levels are lower or depleted, your system won't have the ability to absorb the heat as it used to.
  • Hissing Sounds - If you hear hissing or gurgling (a sign of a larger leak) it could be that there's cracks or holes in your evaporator coil and refrigerant is escaping.
  • Frozen Coil - If you find your evaporator coil frozen, you almost certainly have a leak. When your coil freezes there isn't enough refrigerant within the system to adequately absorb the heat. As the unit is working, condensation forms on the coils and freezes. 

If you suspect your evaporator coils are leaking, you should call an HVAC professional who can confirm the leak and fix the problem for you.

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Evaporator Coil Leak Repair

Unfortunately, repairing an evaporator coil leak isn't recommended. Some homeowners try, but the nature of the design makes repairs unreliable.

The copper tubing curves into difficult-to-see places that can be very, in not impossible to reach. Often the leaks are as small as a pin hole and finding the exact spot can be nearly impossible.

If you've confirmed that you have a leak, you'll need to replace your evaporator coil. Depending on the type and age of your system, you may need to replace your air handler as well. 

In some cases, it may even be the right move to install a new HVAC system. The upside of this decision is that newer systems are far more energy efficient and you'll see the savings every month on your utility bill.

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Preventing Future Evaporator Coil Leaks

As with any major appliance, taking preventative action will help protect it's components and improve the service life. Here are a few things you can do to protect your HVAC's evaporator coils:

  • Routinely vacuum or blow out the evaporator coil and drain pan to ensure minimal debris build-up.
  • Inspect household cleaning supplies and make an effort to eliminate any that contain a volatile organic compound (VOC). VOC's can contribute to the development of formic acid.
  • If the evaporator coils needs to be replaced, consider replacing them with an aluminum coil instead of copper. Aluminum coils are resistant to formicary corrosion.

Evaporator Coil Leak Repair Cost

If your AC evaporator coil is still under manufacturer warranty, the average cost to replace the unit is about $700, assuming  you'll only be paying the labor costs. However, if your unit is out of warranty, for parts and installation the cost will be closer to $1,500. 

Of course, costs vary depending upon the manufacturer and model. We highly recommend contacting a professional HVAC repair service to assess the problem and provide you with the best options for your situation.

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