Air Gap: What It Is, Why You Need One, and Troubleshooting Info

Air Gap: What It Is, Why You Need One, and Troubleshooting Info

Air Gap

When installing a new water softener in your home, you will hear about something called an air gap. It might seem like another part, or some complex set up you need to have that will make installation more difficult, and the idea of just getting this thing installed may tempt you just to ignore that part of the installation instructions.

However, an air gap is actually quite important. Once you learn more about it, you will discover that it is not a huge deal or something that will mess up your installation process. It is quite a simple concept that makes a lot of sense.

What Is an Air Gap?

According to Structure Tech, an air gap is the literal gap of air between the end of the drain hose and the ground or area in which water can gather. The reason for this gap is to prevent contamination in the water softener from the backflow of water.

An example that should make the concept crystal clear is the air gap in your kitchen sink. Your faucet produces clean water, whereas the sink collects dirty or contaminated water. You do not want the dirty water from the sink to get into the clean water or pipes attached to your faucet, so to prevent this, you ensure your faucet is higher than the edge of the sink.

If water backs up and fills the sink, it can no go higher than the sink’s edge. This means the water can’t contaminate your faucet because of the air gap between the end of the faucet and the edge of the sink.

Why Do I Need It?


You want an air gap in your water softener system to prevent contamination of the water softener and its pipes. If backflow occurs and dirty water ends up in your water softener, then you will need to take steps to clean it out. If you don’t, you could end up with dirty water and contaminants in your drinking water system.

Essentially, an air gap keeps you safe and stops bacteria, waste, and other nasty things from getting into water that you may drink or in which you may bathe.

Defining backflow

To really understand how contamination can occur, you need to understand backflow better. Backflow is not simply some water getting into the end of the hose. Backflow occurs when there is a change in pressure.

You have the pressure in the gathering water and the pressure inside of the hose. When they collide, it creates a change that will push the dirty water that is gathering back into the hose. The pressure is enough that it will move that water inside the whole system.

So, if backflow occurs and you don’t have an air gap, you can expect extreme contamination of the whole system attached to your water softener.

Legal concerns

The Minnesota Department of Health explains that plumbing codes also require air gaps as a matter of sanitation. Not having an air gap would mean you have a code violation. While that may not be a big deal to you in most cases, if you have an insurance claim or want to sell your house, then it can become a serious issue.

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How Do I Install an Air Gap?

Since an air gap is not an actual part of your system and is literally just a gap of air, you don’t really have to install it. However, you do need to create it when installing your water softener.

A word about water softeners

A water softener serves as a filter for the water coming into your home. It can remove certain minerals, such as calcium and magnesium. The water flows through the system and into a brine tank. The brine tank contains salt, which will help to remove the minerals from the water. The water then flows out from the tank into your home’s pipes so you can use it for drinking, cooking, and bathing.

The removed minerals will collect in the brine tank. Eventually, you will need to clean this tank to remove the build-up or else the minerals will fill up the tank and make it useless.

That is where the drain hose comes into the picture. You need to drain the tank so that you can scoop or vacuum out the residue build-up.

The common set up for a water softener is to have the drain hose run into a drain on the floor. This works with gravity to allow the water to drain out once you open the valve with little work on your part. It also ensures the water goes into the waste system since it is not useable.

Installing the drain hose

You want to install the drain hose in a way where there is an air gap present between it and the floor. The hose should not touch or connect to the drain or lay on the floor. It needs to hang in the air.

Size of the air gap

The rule of thumb is that you want your air gap to be a length that is two times the drain hose’s diameter. For example, if your drain hose is one inch in diameter, your air gap needs to be two inches. You will ensure the hose hangs at least two inches from the drain.

Plumbing codes will usually dictate the minimum air gap allowed. A common standard is 1.5 inches.

Special considerations


You should also consider splashing when deciding the air gap size.

When water flows out of a water softener drain hose, it will not just dribble out or flow softly. It rushes out. If your hose is above a drain with a cover, the water will hit that cover and splash back on and into the end of the hose.

While this won’t create backflow or large contamination, it still has the potential for some contamination to occur.

It is also important to make sure that there is no chance of the drain hose dropping down or coming in contact with the drain or floor. It needs to be sturdy enough to stay in the air. You don’t want to lose the air gap, especially in a situation where you have the potential for backflow.

What Issues Can Occur with an Air Gap?

The biggest issue with an air gap is when it fails. An air gap can fail due to improper installation or damage to the drain hose.

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Improper installation

Improper installation may occur when you fail to put in an air gap at all. Laying the drain hose on the floor is a good example of a bad installation. You have no air gap, so contamination is inevitable.

Another example is connecting the drain hose to the drain. This may seem reasonable because it ensures anything coming out of the drain will go down the drain and not go anywhere else. However, it also means anything backing up in the drain will go into the hose and increase backflow contamination potential.

You may also end up without an air gap if you run the drain hose into a sink. To do this, the hose would have to drape over the edge of the sink, and as you know from the earlier example, if the sink backs up, it will do so to the edge, so anything below the edge has no air gap.

Hose damage

To avoid any type of failure where the drain hose droops so that the air gap disappears, you will need to use a stiff hose with a strong connection to the water softener. You need to ensure that it will remain ridged no matter the conditions.

Recommended Read: Why Your Home Water Supply is Secretly Ruining Your Life & How Exactly How to Fix It

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Cause of failures

One of the main reasons failures occur is that the installation instructions from the water softener manufacturers do not include proper instructions about installing an air gap. The instructions the manufacturer may include might work in theory, but they may not be reasonable.

The Star Tribune gives an example where the manufacturer suggests securing the end of the drainpipe to a brick that will raise it above the drain surface. This works because it will provide what you need. But once the water runs out of the hose, it will go everywhere, so it isn’t a functional idea.

In most cases, when you have such instructions, it is because the hose the manufacturer included is not rigid enough. You can fix the issue by swapping out the drain hose.

Final Words

shower head

An air gap may seem like a foreign concept, but as you can see now, it really is a simple thing. It protects you from contaminating your water and keeps you within plumbing codes.

When it comes to adding an air gap, you simply need to make sure that the drain hose on your water softener is hanging in the air and not touching the ground or drain in any way. As long as you have this setup, you should be good to go.

Last update on 2021-03-06 at 00:41 / Affiliate links / Images from Amazon Product Advertising API

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