Monday, November 27, 2023
HomeFactsSecondary Condensate Drain Line Dripping

Secondary Condensate Drain Line Dripping

What Are Some Common Drain Line Problems

AC Dripping/Won’t Turn On? 2 Tips Unclog AC Drain Line Pipe

While condensate drain lines are relatively simple devices, they can develop several problems that can potentially damage your HVAC system or your home.


A condensate line can develop a clog when dust and debris that build up on the evaporator coil make their way into the line or mold grows inside of the line.

A common sign of a condensate drain line clog is a condensate pan that begins dripping water around your AC unit. However, if your AC has a special inline safety float switch designed to protect it from the water damage that a clogged drain line can cause, it can instead fail to turn on when water inside of the drain pan reaches a dangerously high level.

Turn your air conditioning system off at the first sign of a condensate line clog. Contact an HVAC expert who can unclog the line to restore proper AC function again.

Mold Growth

Mold growth in your condensate drain pan and line can releases pores into your home air that pose a danger to your family’s health. For this reason, take steps to keep your condensate drain pan and line mold free. One sign of mold growth in your AC drain pan or line is the smell of must or mildew when your AC runs.

If you suspect that mold is growing in your drain line now, have an HVAC expert clean the line. Then, you can help prevent future mold growth by flushing your line with vinegar about once a month.

Drain Pan Failure

Uniform Mechanical Code Section 3100 3101 Condensate Disposal

Here is an excerpt from the Uniform Mechanical Code pertaining to the disposal of air conditioning condensate:

Condensate from air washers, air cooling coils, fuel-burning condensing appliances, the overflow from evaporative coolers and similar water supplied equipment or similar air conditioning equipment shall be collected and discharged to an approved plumbing fixture or disposal area.

If discharged into the drainage system equipment shall drain by means of an indirect waste pipe.

The waste pipe shall have a slope of not less than 1/8 inch per foot or one percent slope and shall be of approved corrosion-resistant material not smaller than the outlet size as required in either Section 310.3 or 310.4 below for air-cooling coils or condensing fuel-burning appliances, respectively.

Condensate or waste water shall not drain over a public way.

To clarify, an indirect waste pipe is something that is upstream of a trap. That means we cannot dump into anything downstream of a trap.That would include the main plumbing vent stack. —

How Do I Unclog My Drain Line

Before we go into the details of how to unclog your drain line, we want to warn you that if youre experiencing the following symptoms, you should not attempt to unclog your condensate drain yourself and you should instead call a professional ASAP.

Don’t attempt to unclog the drain yourself if:

  • Your AC has shut off and isn’t working
  • You see water leaking around your indoor unit”/”your notice water stains from AC
  • You notice that your ceiling is stained

However, if you notice a small amount of water around your indoor AC unit and your house feels a little warmer or muggier than usual, its probably okay to try to unclog your condensate drain line yourself.

Follow these steps to unclog your drain line:

Step 1: Turn your AC off. You can do this from your thermostat by turning your system from COOL to OFF.

Turn your AC off before you try to unclog your drain line.

Step 2: Go outside and try to create an airtight connection between your shop vac and your condensate drain line. If you arent sure how to create a tight connection, you can use your hands, duct tape or tightly wrap a towel around the connection.

Note: if youre having trouble finding your outdoor condensate drain line, it should look something like this:

Drain line.

Step 3: Once youve created a good connection, turn on the shop vac for 1-2 minutes.

If you are having trouble unclogging your drain line this way, you can also try using a garden hose.

Heres how it works:

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Secondary Condensate Drain Line Routing

New horizontal attic install last week, ICP/Tempstar F9MVT 120k 2-stage 96% furnace and TSA6 5-ton 16 SEER compressor put in by local outfit. Coil is matched ENH4X60C, thermostat is new “Observer” communicating. Home is a 2,000 sqft 4 bedroom single-story ranch-style tract home at 1800ft elevation in local foothills, with a very open floor plan. Build date was 1963, had the original 1963 Lennox GS6 130k furnace and no A/C. Got new ducts, a standard SoCal attic flex ductopus with the install, too. Using half old register boots and half new, passed California HERS test at 372 CFM leakage. Single zone for whole home.Below are a few pictures of the condensate drain line routing. Primary has trap, vent, then furnace tie-in, then off to the eaves and down to ground level. Secondary routes up and over the primary, and down into backup catch pan. Backup pan drain is over to a different edge of the attic, comes out above a window.Question: how does this secondary routing from the coil into the backup catch pan ever work? It requires the water to flow up against gravity first, then horizontally for a bit, and then down into the pan?Wife is having ceilings re-plastered, and having been in a home where a primary condensate drain failed before and ruined the furnace due to lack of a secondary, I want to make sure the secondary drain is going to work right on this new install and protect the new ceilings.Thanks!

Always Keep Your Drain Line Clear

Condensate Lines correct? Secondary leaking into tub after flush

Regularly clearing or flushing your drain line is one of the best ways to lower the chances of overflow and clogging. It only requires you to locate the pipe and run clean water through it.

You can also add a cleaning mixture to ensure any dirt buildup gets eliminated before it grows. However, be sure to use the appropriate cleaning solutions before applying them.

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Is My Ac Drain Line Clogged

When air comes out of your drain line, it usually indicates clogging. A condensate drain line primarily functions as a funnel for air to go in and out while the system runs.

Traps are installed to keep air from coming through while allowing water to drain from the condensate pan. It prevents moisture build-up, resulting in less damage to the ductwork and insulation.

A clogged drain line poses a risk to the overall comfort in your home or your system, so watch out for different symptoms that point out the possible blockage.

Other than having air come out of your drain line, here are a couple of signs to look out for suggest clogging:

  • Your air conditioner has trouble cooling your home.
  • Your air conditioner excessively drips water.
  • Your air conditioner fails to turn on, or the system shuts down.
  • You notice a damp or moldy smell.

How Much Water Should Be Coming Out Of The Exterior Pipe On Your Ac

Ever wondered why ACs are called air conditioners and not air coolers? Its because they place as much emphasis on humidity extraction as they do on heat removal. Dry interior air simply feels a lot cooler and more pleasant to occupants.

Of course, all that moisture thats being taken out of your house doesnt just vanish. It gradually builds up inside your air conditioner and is then conveyed to a drain pan via a condensate drain pipe. A damaged AC condensate drain pipe can cause all sorts of problems such as reduced cooling capacity and water dripping out of your AC.

But how can you tell if your drain pipe is working as intended, or if its time to schedule air conditioner repair in Queen Creek? How much water should drain out of an AC on a normal summer day? Read on to learn more.

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How Does A Condensate Overflow Switch Work

An HVAC wet switch/float switch, also known as a condensate overflow switch, serves to prevent this pan from overflowing if the AC drain stops working properly. The switch is activated when the level of the water in the pan comes above a certain point, causing the switch mechanism to trip/float to rise.

How Much Water Should Drain From Air Conditioner

HVAC with no secondary drain line. Why is it an issue?

Generally, any water coming from the secondary/exterior condensate drain pipe is too much because the primary drain line is designed to handle all condensate drainage needs if all is well.

According to SFGate, many central air systems remove at least five gallons of moisture daily and the primary drain line handles it with no fuss. A larger sewer-connected drain line can even handle 20+ gallons of condensate per day.

So, if you see the water dripping from the exterior AC drain pipe, then either your AC is generating an excessive amount of water or not passing the normal drainage as the manufacturer/installer visualized .

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The Air Conditioner Evaporator Coil Is Frozen

Over time, an air conditioners evaporator coil can freeze and accumulate ice under the air conditioner. Determining whether or not this is whats happening to your AC will require you to get closer to see if you have frozen evaporator coils. A professional HVAC technician should do this inspection so it pays to check with them before you attempt any changes.

Clean And Unclog The Vent Tee

The vent tee is located near the air handler. It usually has the top of the tee capped off with a plastic piece.

The vent tee serves as an access point to clean the condensate line. Remove the plastic cap and take a look inside the tee. You might find some slime build-up inside there! If so, youve found the source of your clog.

To clean out the vent tee, use a wet/dry vacuum to blow air through the tee. You may need to wrap a rag around the vent tee to form a seal with the vacuum hose.

If your vacuum is not strong enough to remove the clog from the condensate line, then you can use a drain gun instead. A drain gun will inject high-pressure gas into the drain line. The high pressure will remove almost any clog.

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How Do I Fix A Drain Pan Full Of Water

There are several reasons why your air conditioners drain pan is full of water. Regardless of what you do or how it ended up that way, here are a few ways to fix the problem:

If your drain pan is full of water and none of those options work for you, call a professional to take care of it. After all, they have the proper tools for this kind of job.

You could try fixing it yourself if youre not worried about spending money or handling electrical components, but theres always an inherent risk whenever you go tinkering with machinery. Professionals know the ins and outs of these machines and can address any issues without putting themselves at risk. They also usually come equipped with their own tools and materials to get the job done.

If youre not very handy or dont want to break a sweat, then you can hire a professional who will do it for you. They have the equipment and experience necessary to fix your AC so that it works perfectly again.

Most companies provide homeowners with a maintenance plan so they dont have to worry about such minor issues as drain pan full of water or an A/C that doesnt work properly. Its best if they address the problem right away before it affects your health and safety, but in some cases, these things can wait until theyre due for servicing anyway.

How Does A Condensate Drain Pan Work

HVAC Secondary With Condensate Water

The primary purpose of the condensate drain pan is to collect excess water that comes from the air conditioning process. But where does this water come from?

When the thermostat is set to cool, the evaporator coil, part of the central air system and found in the furnace, fills with compressed refrigerant. This A-shaped coil drops to very low temperatures and get very cold.

Moist, warm air from inside the home enters the HVAC system from air ducts. It then passes through the air filter and into the open center of the evaporator coil.

This is where a heat transfer takes place. Moisture and heat are pulled from the air. The now cool air is then pushed through the air ducts and into the house.

As the heat transfer goes on, condensation creates excess water. Its similar to a glass of ice water on a hot day. After a few moments in a warm environment, the glass is covered in beads of water. In the same way, tiny water droplets collect along your evaporator coil. Water slips down the sides of the evaporator coil and right into the condensate pan fitted below.

This process continues until the air conditioning is turned off. The condensate drain pain is installed to safely collect any water that drips off the evaporator coil. Then, a condensate line in the pan moves water out of the home, emptying to the sewage system or another external location.

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Technical Reviewers & References

A Homeowner’s Guide To Air Conditioner Condensate Drain Lines

Many central air conditioning systems have a condensate drain line. You must keep this line clean and in good condition to keep your air conditioning system functioning properly. A drain line that doesn’t work properly can cause your air conditioner to work less efficiently or even stop working at all. In addition, drain backup scan lead to extensive home water damage.

Learn more about how your AC condensate drain line works, along with common drain line problems you should watch for.

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Why Your Drain Pan Is Full Of Water

If you notice that besides the dripping water, your drain pan is also full, the following are the most likely causes

  • The drain line is clogged: If the primary drain line is blocked, condensate has nowhere to go. So, it will accumulate in the drain pan.
  • The evaporator coil is dirty: Dirty evaporator coils often result in air conditioner freezing, causing excess water in the AC.
  • Incorrect AC installation: Finally, your drain pan may also fill quickly if the AC is poorly installed or incorrectly sized.

Why Is A Clogged Drain A Problem

Plumbed Primary A/C Drain Line Location

When the condensate line is completely blocked you could see distressing signs of water leaks in your home which may be difficult to distinguish from a plumbing or roof leak, especially in monsoon season. When your condensate pan overflows it can cause corrosion of metal parts of your ductwork and HVAC equipment and hundreds of dollars-worth of damage to drywall, carpentry and flooring.A partially blocked, poorly draining condensate line can decrease the effectiveness of your otherwise highly efficient air conditioning equipment and cause musty odors from bacteria, algae and mold growth.

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How To Clean Ac Condensate Drain Line

To clean the drain system, shut down the air conditioning unit at the circuit breaker and unscrew the access panel to locate the drain pan.

The drain line is located at a saturation level under the evaporator coils. If water is overflowing in the pan, use a vacuum cleaner to get rid of the clog. Alternatively, use a suction pump.

We recommend working from outside the house for the best results.

Primary And Secondary Lines


Many units that are located in attics or similar places will have two condensate lines. One is the primary condensate line that is generally connected to a location, like a tail piece of a bathroom sink drain piece.


The secondary line is considered a backup line, so that if the primary line gets clogged, the condensate water will then go through the secondary line. The secondary line will often end in a highly visible and conspicuous location.


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Heating And A/c Overflow

We highly recommend you have your HVAC system serviced by a professional in the spring and fall. To kill fungus, prevent organic buildup, and keep your primary drain running smoothly, pour one cup of a 50/50 solution of bleach and water into the opening at the condensate drain line where it leaves the evaporator coil. Doing this in the spring and fall will also help prevent condensate from backing up and flooding.

What Happens When Condensate Drain Line Clogs

A/C Condensate lines

Your air conditioner cannot release condensate water when your drain line clogs, so the condensate remains inside the pipe or in the drain pan, resulting in several problems.

When condensate stays stuck inside the drain line, it could result in corrosion or rusting of the metal parts that get in contact with the water. It could shorten your system’s lifespan and require costly repairs.

On top of that, water won’t be able to pass through for drainage, meaning it will continue to accumulate as long as your air conditioner is running. In this case, your system would be in great danger of needing excessive repairs, complete replacements, or even major harm.

If condensate water evaporates in the drain pan, humidity levels increase within your home. Besides the uncomfortable and sticky air, it also leads to property damage due to mold and mildew growth. It can also put you at risk for health complications.

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