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The Hazards of a Clogged Primary A/C Line: Why You Should NOT RELY on The Secondary Drain For Backup

Updated: Feb 22

Your home's air conditioning system plays a crucial role in keeping you cool and comfortable during the sweltering summer months. However, there is a hidden danger that homeowners need to be aware of - a clogged primary A/C line. We will explore the potential risks and damages associated with a clogged primary A/C line and why relying on the secondary drain line as a long-term solution can lead to even more problems.

Understanding the Primary A/C Line and Its Function:

The primary A/C line is responsible for carrying condensate water, which is produced during the cooling process, away from your air conditioning unit. This line is designed to drain the water properly, preventing it from backing up into your home. However, over time, the primary A/C line can become clogged due to debris, algae growth, or other blockages. The condensation produced from the A/C unit typically carries harsh metals that clogged the primary drains over time. This is why systems have a secondary line to help in case the primary gets clogged.

The Dangers of Relying on the Secondary Drain Line:

In some cases, when the primary A/C line becomes clogged, homeowners may notice water draining from the secondary drain line. The secondary A/C line is responsible for draining excess water that accumulates in the A/C unit's pan, and if it becomes clogged, the water can back up and overflow into the home. This can cause damage to walls, ceilings, and floors, and create an environment for mold to grow, which can be hazardous to your health.

While this secondary line is a temporary backup, it should not be relied upon as a long-term solution. This is why installers put them in obvious locations, like over a window, for example, it's to alert the homeowner that the primary is clogged.

The Consequences of a Clogged Primary A/C Line:

When the primary A/C line becomes clogged, the excess water has to be redirected through the secondary. Depending on the installation, this can lead to a variety of issues, including:

1. Water Damage:

The backed-up water can overflow from the A/C unit's drain pan and seep into your walls, ceilings, and floors. Over time, this water intrusion can cause significant damage, including rot, mold growth, and structural deterioration. Repairing water damage can be costly and time-consuming, impacting both your finances and your home's value.

2. Mold Growth:

Stagnant water provides the perfect breeding ground for mold and mildew. When excess moisture is present in your home, it can promote the growth of harmful mold spores. Mold not only damages surfaces but also poses health risks to you and your family. Respiratory problems, allergies, and other health issues can arise from prolonged exposure to mold.

3. Damaged insulation:

This not only affects your home's energy efficiency but also puts a strain on your HVAC system, leading to higher energy bills. As soon as insulation gets wet, it's damaged and no longer achieves its original designed R-value. Wet insulation can also lead to mold growth and other health hazards. This is important to understand to keep homeowners healthy.

Real World Examples:

Most of the problems we find are due to uneducated homeowners who are unaware of the secondary drain and it's function. We make sure and inform all of our customers, during the final walkthrough, the location and function of the secondary drain for the A/C system.

Example 1:

The accompanying photo illustrates water flowing from the secondary condensation line of the A/C unit, resulting in a noticeable rust stain on the home's brick exterior. Fortunately, the buyer took proactive measures by negotiating repairs prior to closing, ensuring that the issue was resolved before moving in. The proper repair involved clearing the primary line to facilitate unrestricted flow, ensuring the secondary line remained unobstructed. Additionally, a reputable power-washing company skillfully eliminated the rust stain, performing a minor miracle to restore the home's aesthetic appeal. It is crucial to entrust both tasks to professionals to mitigate the risk of further damage to the property.

The left photo is before, it shows a rust stain on the brick wall from the secondary a/c drain. The right photo shows after it was cleaned by a powerwashing company.

Example 2:

In the video showcased below, you can witness the steady flow of water from the secondary drain line. Unfortunately, due to an extended period of water discharge, mud dobber insects managed to clog the secondary drain line as well. As a result, the home suffered from unsightly ceiling stains and damaged insulation. Although both drain lines were eventually cleared, and the necessary repairs were carried out, it's important to note that addressing the issue promptly when the homeowner first noticed water coming out of the secondary drain line would have been a more cost-effective solution.

Example 3:

In the video displayed below, we witness a concerning scenario where the secondary condensation line has been discharging in an improper location for an extended period. As a consequence, condensation has leaked onto the A/C unit, resulting in severe damage. The homeowner was unfortunately compelled to replace the entire outdoor unit due to the extent of the harm inflicted. To prevent any future damage, it is imperative to consider relocating the secondary line to a more suitable position. By doing so, you can safeguard your A/C unit and avoid costly replacements or repairs down the line.


In Texas, it is important to have the primary and secondary condensation line systems installed professionally due to the high temperatures we experience. After about 8-10 years, it is common to find that your primary is clogged in Texas particularly. A clogged primary A/C line is not something to be taken lightly. It can cause extensive water damage to your home and create an environment for mold growth. Relying on the secondary drain line as a long-term solution can lead to further complications. Don't let a clogged primary A/C line become a costly nightmare - take proactive steps to protect your home and your investment. The repair is actually rather cheap and most companies will clear your line for around $100 which is equivalent to their trip fee.

About TruGuard Inspections:

At TruGuard Inspections, we take pride in delivering top-quality home inspection services to clients throughout the DFW Metroplex. Our experienced team is dedicated to providing thorough and detailed inspections, utilizing the latest tools and technology to ensure no aspect of the property goes unnoticed. Whether it's a buyer's home inspection, seller's inspection, new construction inspection, 11-month warranty inspection, or thermal inspection using infrared cameras, you can rely on us to provide honest and insightful assessments for informed decision-making. Check out our website to learn about all the services we offer.

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