Dishwasher Air Gap Required

During the home inspection I often get asked whether or not an air gap is required to be installed on the dishwasher drain line.  The short answer to this question is yes.  Modern standards require an air gap for all new dishwasher installations.  Notice the words I used, “modern standards” and “new installations.”  The existence of a high loop on an older dishwasher may very well have been allowed under code when the unit was installed.  However, this does not mean that a home inspector will refrain from recommending an update to the modern standards by installing an air gap.

You might be wondering, “but you said that the standards only applied to new installations.”  While that it is true, there is a reason why standards and codes have evolved.  We have learned more regarding safety and efficiency, which are factors that help shape the standards.  It is for health and safety concerns that the local AHJ (Authority Having Jurisdiction) wants an air gap installed for dishwashers.

Backflow Prevention

An air gap is required by modern standards due to backflow concerns.  Backflow is the term used when wastewater enters the potable water supply, also referred to as a cross contamination.  If wastewater were to backup into the dishwasher, there is a potential for the wastewater to siphon through the dishwashers water supply in the event of a pressure loss in the system.

What About Built in Anti-Siphon Protection?

Built in dishwasher anti-siphon protection does not fulfill the requirements laid out in current standards.  After speaking with the local AHJ in my area, it has been made clear that the municipality wants to see a physical separation to prevent the potential for backflow.  This physical break is achieved by installing an air gap.

Missing air gaps are likely to be called out on an inspection as a recommended upgrade.  This can be viewed as deferred maintenance, along with such items as updating or installing GFCI and AFCI protection for electrical outlets.  If you are buying a home with an older dishwasher that has a high loop, it would not be considered a material defect.

We comment on the presence or lack thereof regarding dishwasher air gaps in every home inspection report.  Call us today to schedule your next home inspection, 760-675-5463.