Air Gap: Installation and Importance in Plumbing

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It is funny how everyone takes for granted so many little things that protect them and/or facilitates their life – clean, drinkable water being one of those things. You don’t appreciate how important it is until you don’t have it.

If you are fairly privileged, you have a constant clean water supply. This can all go away and cause contamination of clean water if you don’t have or don’t properly preserve air gaps in your home.

Such a small device is of utmost importance for our well-being. So, let’s establish what it is exactly.

air gap plumbing

What is an Air Gap?

In Layman’s terms, an air gap is a backflow prevention “device”. In this context, the term “device” is used quite broadly, since an air gap is not a device. It is a gap – an unhampered vertical space that restrains potable water and wastewater from meeting and contamination.

An air gap is located, according to Wikipedia, “between the water outlet and the flood level of a fixture”.

Air gaps are customarily found in water fixtures such as sinks and kitchen appliances such as dishwashers.

Additionally, in many countries, one is obligated by law to have a dishwasher with an air gap installation.

This is because it is not only your house water that becomes non-potable but since the majority of people get their water supply from a shared system, the whole town will suffer, just because of one irresponsible individual.

Installing this device will require a licensed plumber.

So, how does an Air Gap Work?

So far, we have established that it prevents wastewater from mingling with potable water. It should be mentioned that this isn’t the only backflow prevention device, but it certainly is the simplest and most effective.

Even with a perfectly installed and maintained air gap, one can experience backflow. However, this does not mean you shouldn’t have one.

In plumbing systems, potable and non-potable water are predetermined to flow in different parts and never intersect. If they do, backflow occurs. Furthermore, providing this happens, it can prove hazardous for our health – it would lead to poisoning, and in extreme cases, to death.

Therefore, backflow is a process in which wastewater is unable to find the right pipe through which it is supposed to flow and enters the freshwater pipe. Moreover, this contaminated water can then travel to the main water supply line.

Let’s see how it works with our sinks and dishwashers.

Sink Air Gaps

This is the most common and most literal example of an air gap. It is strongly advisable that the faucet is installed considerably higher than the flood line. Why?

Because the faucet is a water outlet and the basin is the water receptacle. When we turn on the water, that water travels through empty air into the basin. Water that leaves the faucet flows across empty air into the basin.

sink air gap

Even assuming that the basin stops draining and the water subsequently backflows to its flood level brim. Owing to this space between, dirty water will not reach the faucet.

Contaminated water and other grimy debris that might backflow will remain in the sink itself.

Without an air gap, consequences are severe.

It must be noted that if you don’t have an air gap in your sink; it doesn’t necessarily mean you will face backflow. But it can happen if the water supply pressure becomes low, or if the sink is placed well above the water supply access point.

Another very commonplace for an air gap is a kitchen appliance almost everyone has – a dishwasher.

Dishwasher Air Gaps

As previously mentioned, most plumbing codes do require air gap installation in dishwashers.

This should not be seen as a frivolous annoyance that you seek to avoid, but a smart way to provide safety for your household and preserve non-potable water from entering your dishwasher.

Whereas you can get away without a considerable air gap in your sink, a dishwasher without this installation is going to become contaminated with wastewater.

The air gap is usually integrated into the dishwasher installation. On the surface, you see it as a tube that is placed a couple of inches above the sink. Beneath this tube under the sink, there are two branches.

dishwasher air gap

First branch adheres from the dishwasher to the air gap.

The second branch goes down from the air gap into the designated drainage line.

Hence, when the dishwasher hose runs the wastewater out of the dishwasher, it curves upward.

At the top, the branch ends and the water flows through the open tube (that is visible on the surface) and through the second branch. The water flowing through the second branch is the wastewater and other debris.

You can encounter air gap leaks, which are the sign that the drainage pipes are clogged.

Although these are examples of something everyone has in their homes, if you like to filter your drinking water, there is another place where an air gap is found.

The Reverse Osmosis Water System

Other places where air gaps are necessary are in reverse osmosis (RO) water systems. Even though there are some that believe that RO water is not the greatest way to treat your drinking water, RO remains one the most popular, safe, and efficient water filtration system for households.

Simply speaking, RO functions in a way that pushes water across a partly absorptive membrane or sheath, and thus all toxins and impurities (aka brine) are left behind and flushed down the drain.

Therefore, if the RO is connected to the main drain line, the air gap is essential for safety reasons.

Conclusion: Importance of Air Gaps in Plumbing

If you did not believe in the importance of air gaps in plumbing systems, I do hope this brief elaboration changed your mind. Air gaps save not only our households and those living with us, but it also saves everyone else.

With a shared water supply system everywhere, if you're not careful you could endanger whole towns and cities.

All in all, if it is not legally required to install an air gap in the place you live in, it does not underestimate their significance in our everyday lives.