Do Bosch Dishwashers Need an Air Gap?

Depending on where you live, you may have heard that air gaps are necessary for every dishwasher that is installed. However, you may have also heard that Bosch dishwashers are exceptions to this rule. Do Bosch dishwashers need an air gap?

Bosch dishwashers do not need an air gap if the drain hose is elevated at the recommended height to prevent cross-contamination. Some local codes require air gaps, but home inspectors may make an exception for a Bosch dishwasher. However, air gaps are more reliable compared to the alternative.

Bosch dishwasher

If you’re still unsure what to do, read the rest of this article. I will explain why Bosch dishwashers sometimes may not require air gaps and what you need to do to ensure the dirty water doesn’t go back in. I’lls also explain all there is to know about air gaps and how they work.

Why You Need an Air Gap for Your Bosch Dishwasher

Dishwashers have two different hoses, one tasked with supplying clean water and the other with taking the dirty water away. These are basically the main functions of the dishwasher, so these hoses are essential to the whole process. If you’re having issues with drainage, check out my other article that explains what to do when your dishwasher isn’t draining properly. 

Traditionally, a dishwasher needed a system to ensure that these two hoses never communicated in any way. Otherwise, the dirty water could come back into contact with the clean dishes. This would not only render the dishwasher useless, but it could also pose risks of contamination.

An air gap ensures that the wastewater is removed and cannot be siphoned back, which is why it has become a requirement for every dishwasher, even Bosch. Professional installers or Bosch installation manuals will inform you about the air gap and why it’s required.

Moreover, local plumbing codes may require an air gap. This means that licensed plumbers have the right to refuse to install your dishwasher if you don’t have an air gap. You need to check your local plumbing code to find out whether installing an air gap is a must or not. For instance, in California, you need an air gap for your dishwasher, regardless of the brand.

full loaded Dishwasher machine

When Is an Air Gap Not Required for a Bosch Dishwasher?

You might wonder why you’d even consider not including an air gap if they are crucial in making your Bosch dishwasher work. Well, for modern dishwashers, air gaps may be on their way to becoming obsolete soon. Bosch, in particular, is already known as an exception when it comes to air gaps. 

If you check out a Bosch dishwasher’s installation manual, you’ll see that it includes a scenario where you don’t need an air gap at all. The instructions state that if there is no air gap, your Bosch dishwasher will still work well with no chance of wastewater re-entering if the drain hose is elevated.

Basically, the hose that disposes of the dirty water needs to be placed at a higher level than the water level on the sink. This is called the high loop method, an alternative to installing an air gap. Many modern dishwashers these days offer this alternative to air gaps, thanks to valves that direct the backflow to avoid flooding the dishwasher’s interior with wastewater. 

Because high loops have become an acceptable way of replacing air gaps, many states no longer require air gaps for dishwasher installation. If you live in one of these states, you don’t need a Bosch dishwasher air gap.

Why Do Plumbing Codes Still Require Air Gaps?

As mentioned in the previous section, the high loop system can be a great alternative to the air gap method to prevent backflow into the dishwasher. However, many states still require an air gap to be installed because air gaps are considered a safer choice. If a backflow valve is faulty, a high loop system can be more easily compromised than the air gap.

In general, Bosch dishwashers have become the only exceptions to this rule. Installers and home inspectors will let you know when you need to install an air gap according to the code, but some may let you use the high loop system if you specify that you’re installing a Bosch model.

To ensure that you’re complying with the rules and that you’re entirely safe, check the plumbing codes in your state or ask a home inspector in your area what you should do. 

repairman fixing dishwasher in modern light kitchen, holding screwdriver in hand, looking inside dishwasher

Air Gaps vs. High Loops

To better understand why air gaps are required and why high loops may work as ways of replacing them, you should have an idea of how each of these methods works:

Air Gaps

The air gap ensures that the clean water supply and the wastewater never mix by separating the hoses with a physical air gap. It’s located close to the sink, with one branch connected to the drain hose and the other to the garbage disposal. 

In general, an air gap is considered a foolproof and safe way of preventing cross-contamination between clean and dirty dishwasher water, the reason it’s a requirement for most dishwashers. Air gaps usually need to be professionally installed.

High Loops

High loops have the same purpose as air gaps but have a much simpler way of working. In simple terms, a high loop system requires the wastewater hose of the dishwasher to be elevated near the sink before it connects with the vertical sink drain pipe.

By elevating the hose, you ensure that the wastewater doesn’t go back the wrong way and flood your dishwasher. You should aim to elevate the hose as close to the top of the counter as possible. You can install a high loop by yourself, even just use zip ties to do it, but it’s better to consult a professional to make sure you’re safe.

Today, Bosch manuals and home inspectors allow high loops to serve as the safety system against contamination, so you should be fine even if you don’t install an air gap.


Air gaps have traditionally been required as a way of making sure the clean water and the wastewater in your drain never come into contact with one another. Do Bosch dishwashers need air gap? Well, Bosch dishwashers allow you to forgo installing an air gap using the high loop system.

Some local plumbing codes always require installing an air gap, but some inspectors may consider Bosch as the only exception and not require it. However, air gaps are still safer and more foolproof than high loops.