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What is a drain air gap and why is it important to your home?



If you’ve recently installed a new dishwasher or are planning to, you’ve likely heard people talk about putting in an air gap kit to go with it. Air gaps are small, cylindrical fixtures that sit on your sink rim and block the re-entry of contaminated water into the dishwasher from the drain if backflow occurs. 

No one wants wastewater mixing with their clean water supply. Air gaps are now common components of official plumbing codes in many states for their ability to prevent contaminants from infiltrating potable water. This article will discuss the function, necessity and cost of air gaps for your home.


What is a drain air gap?

An air gap is simply a small addition to your countertop that sits to the side of your sink, generally at the top corner nearest to your dishwashing machine. The air gap resembles a short, squat cylinder that may appear to have open valves on one or both of its sides. 

Your sink faucet sits several inches higher than your sink rim to protect against sink water overflowing to the point that it could re-enter the faucet line where your clean water comes from. An air gap for your dishwasher does the same for that appliance. In the event that your dishwasher drain line experiences a clog, the air gap makes sure that contaminated water never mixes with the clean water supply intended to wash your dishes.


How does an air gap work?

In order to maximize the benefits of your air gap installation, it is important to fully understand how these plumbing fixtures work. Beneath the kitchen countertop, a drain hose runs from the dishwasher to the top of the air gap. 

The bottom of the air gap can either siphon water into the drain line of the sink or into a garbage disposal. This means that the water flow coming out of the dishwasher never has the opportunity, even if it reaches flood level, to mix with your kitchen’s clean water supply. The air gap serves the function of ensuring that two totally separate hoses are responsible for running clean water and dirty water.


Why is an air gap necessary for your home?

Building codes in many states have evolved to the point where any plumber contracted to construct new kitchens may be required by law to install an air gap kit. Backflow prevention has been recognized as a crucial component of a safe kitchen for a variety of reasons. The idea of unsanitary water being filtered back into what should be clean dishes is off-putting at the least and dangerous at the worst. 

Cross-contamination of dirty drain water into your potable water supply can lead to bacterial infections and illness. Because dishwashers are associated with your kitchen’s drainage system, the possibility of dirty water being siphoned back into the appliance and causing it to do the opposite of its intended job is something you definitely want to avoid.

Air gap systems are meant to replace older methods of kitchen drainage, such as the popular high loop design. With the high loop technique, the dishwasher drain line is “looped” as high as it can go under your kitchen countertop and then fed back down to connect to the drain. While this drainage style is still permissible in some places, the air gap system has replaced it in most cases. Homeowners should check plumbing regulations in their area to find out if air gaps are required by law.


Do you need to do anything with the air gap?

When functioning properly and set up correctly, the dishwasher pump should automatically move wastewater through the air gap, which then funnels it through the drain hose to your disposal unit. 

However, we all know life inside and outside the kitchen does not always go as planned. Ordinary places in your plumbing, such as the P-trap in your sink’s drainage system, need attention to stay free and clear of standing water or trapped food particles. The following sections offer details on how to best maintain your air gap’s consistent functionality and provide some simple air gap upkeep tips.

How to clean a drain air gap

Anything involving water filtration has the potential to fall victim to clogs. Whether large or small, a clog can cause your dishwasher drain hose to not be able to funnel the dirty water to the air gap where it can be expelled away from the clean water. 

If you see water flowing freely out of your air gap’s valves, this is a sure sign of a clog. There are a few DIY steps you can take before calling in a professional plumber.

  • Repurpose a paper towel tube. Your air gap has a cover that can be removed if needed. If you suspect your air gap is clogged or malfunctioning, start by taking off its cover and replacing it temporarily with the cardboard inner tube of a roll of paper towels. Blow into the paper towel tube to dislodge small food particles that could be causing the issue.
  • Use a bottle brush. For slightly more aggressive cleaning of an air gap, utilize a bottle brush to clear the blocked drain hose.
  • Check for a knockout plug. If you have a new dishwasher, you may not have a clog but rather a still-in-place knockout plug that needs removing. To find out, detach the hose that connects your air gap drain line to your garbage disposal. With a screwdriver, firmly tap the knockout plug, which looks like a small octagon blocking the flow channel going toward the disposal unit.

For serious problems involving appliances in your home, or even just for those you don’t want to face on your own, Cinch Home Services protection plans can take the worry out of necessary repairs.


Where are air gaps required?

A few states have gone ahead and taken the initiative to make air gaps a formal part of building codes for new construction. Those areas currently include Hawaii, Minnesota, Washington and California. New homes or kitchen renovations in these places will come with mandatory air gap installation, and more states will likely follow this sanitation guideline shortly. 

Another consideration is that air gaps are not just for the kitchen. Other areas in the home that feature a standpipe could benefit from having an air gap fitting. Such locations might include your home’s washing machine, dehumidifier or water softener device.


How much do air gap repairs cost?

Whether made of PVC or metal, air gaps have openings notched into them to vent water through in the event of a drain hose clog. However, most homeowners know that things can always go wrong unexpectedly with household appliances. 

While air gaps themselves can be obtained for between $10 and $30 at standard home-supply stores, installation can run to a grand total of between $110 and $270. Depending on the style of air gap system you choose and your general plumbing skills, this installation can be a relatively easy DIY project or one you feel needs to be entrusted to professionals.

Cinch plans include home appliance warranties that can save you money in the event of an issue with your dishwasher and air gap kit.


Dishwashers and plumbing systems are covered under a Cinch warranty

With Cinch protection plans, homeowners can rest easy knowing the plumbing features of their abode are covered. Air gap systems fall under Cinch’s Built-in Systems Plan and standard plumbing coverage. Don’t let worries about breakdowns get in the way of your life’s stress-free flow. Trust Cinch to keep your air gap and other in-home systems and major appliances going. Get your instant quote from Cinch today! 


Learn about your sink’s air gap and why it matters to your home.