Can My AC Condensate Flood my House?

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Air conditioning is essential for the hot Texas weather. Most of us have had our AC serviced at one time or another. When the AC goes out, we tend to react pretty quickly. Fortunately, an AC failure doesn’t usually cause damage to the home. However, there is one area where AC and plumbing intersect which holds the potential of causing water damage. It is the AC condensate drain. It isn’t something most people pay much attention to until water starts dripping from the ceiling! Read on to discover everything you need to know about AC condensation and how to protect your home from water damage.

What is an AC condensate?

Simple: In simple terms, whenever the air conditioning unit runs it extracts moisture from the air – so much moisture that it can actually be a steady trickle of water coming off of the AC unit inside the house.

Advanced: To go a little further, it has to do with the relationship between the temperature of the air and how much water vapor it will hold. Warm air can hold more water than cold air.

The part of the air-conditioning unit that gets really cold is inside the house, and it is called the evaporator. This is a set of pipes and fins called a heat exchanger which is designed to absorb the thermal energy from the air into the refrigerant that flows through the pipes.

So whenever warm, moist air comes in contact with the cold pipes inside the air-conditioning unit, the air itself suddenly gets colder. When that happens, it can no longer hold all of the water that is in it, and this water condenses on the heat exchanger.

It is the same process that causes water droplets to form on the outside of a cold iced beverage on a summer day. It’s more than a few drops though. The amount of water extracted from the air on a regular basis on hot, humid days is significant. It has to have a place to go.

Where does the AC condensation drain to?

In North Texas, the “inside” part of the air conditioning unit is usually located in the attic. If not, it is probably in a closet inside the house. Most houses built within the last 30 to 40 years have a special drain that collects all of that condensed water from the air-conditioning unit and pipes it to the drain pipes underneath a lavatory sink or in the wall to a tub drain.

This drain is called the primary air-conditioning condensate drain line. If it gets clogged, then the condensation water backs up into the air conditioning unit and goes into the secondary emergency drain pan or drain line.

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This is usually plumbed to the exterior of the home and terminates in the soffit above a window or in another conspicuous spot. This usually looks like a little white pipe that sticks out of the underside of the edge of the roof. This is sometimes called the tattletale drain because once you see it dripping, you know there is an issue with the primary drain line that needs to be addressed.

What happens when the condensation drain gets clogged?

They plan for the condensate drain line to get clogged. It’s going to happen. If there wasn’t a “plan b”, then as soon as the condensate line backed up, it would start dripping in your home and cause water damage!

There are different common ways they design the system to protect your home from getting damaged. There is the tattletale drain we talked about earlier which drains the catch-pan underneath the unit to the exterior of the home. But what if this gets clogged? Some air-conditioning units have a float switch in the pan or inline with the pipe which shuts off the unit if the water level starts to back up.

Most older homes in our service area which have the air conditioning unit in a closet do not have any sort of tattletale drain. There is just the dedicated primary condensate drain which goes to a hub drain in the floor in the closet. If the primary drain line clogs up in this setup, it usually trips a float switch to shut the unit down

How do you service an AC condensate drain?

Whether you do it yourself or have an air conditioning company take care of it for you, the air-conditioning condensate drain needs regular maintenance. These drain lines are very small and they clog easily. Condensation is also prone to buildup of gunk and bacterial growth. Using a cleaner on a regular basis can help prevent this gunk from building up as quickly.

A more thorough job of servicing this part of the air-conditioning system will involve cleaning the evaporator coil to get rid of buildup that may end up inside the condensation discharge. In addition, there are several products that can be put down the air-conditioning condensate drain line that will inhibit bacterial growth.

Every once in a while, the drain line needs to be purged with compressed air when it gets clogged. The air-conditioning condensate drain line is too small to run a traditional plumbing auger or snake through to clear it out.

The only non-destructive way to clean out this condensation line is to blow out whatever buildup can be blown out with compressed air. While it is sometimes possible to do this without cutting into the drain line, most of the time some fittings will have to be added to assist with this purging process.

What can the homeowner do to maintain the condensate drain?

As a homeowner, one of the things that you can do is introduce a little bleach into the condensate drain line periodically during periods of high use. While this does slow down the bacterial growth, it does not prevent the drain line from stopping up entirely. Here’s how to do it:

Near the unit up in the attic, there should be a little port or pipe opening connected to a tee fitting on the drain line. This is usually less than 1 foot away from the unit. This is true for most air-conditioning unit setups in North Texas.

You can use a funnel on the top of this pipe opening and pour a cup of bleach down every couple of months. This will certainly help slow down the gunk buildup. However, this will not clear any clogs that have already started to develop inside the line. For that, you will need a compressed air set up. This is best done by a plumbing or hvac professional.

If you have any more questions, feel free to reach out to us. While the information above is accurate to most AC setups in North Texas, there are a lot of different variations. Furthermore, there are many times stuff is not done correctly or up to code and flies under the radar. Let us know if we can assist you further!


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