Gravity and engineering keep your dishwasher sparkling clean
A dishwasher air gap prevents contaminated water from backflowing into your dishwasher, while alternatives to a dishwasher air gap include Studor vents or loop designs.
Expect to pay $75 to $150 per hour for a plumber to install your air gap, with full dishwasher installation ranging from $1,000 to $1,500.
Check that you've removed the knockout plug from your garbage disposal before connecting the air gap, as this prevents proper drainage and backflow issues.
Hiring a local plumbing professional keeps installation on track when you need countertop drilling or have serious dishwasher clogs beyond the air gap itself.
If you have ever wondered what that extra knob is next to the kitchen faucet, wonder no more—it is an air gap. Dishwasher air gaps prevent dirty water from backflowing into the dishwasher or entering your clean water supply. Dishwasher air gap installation is not difficult. In fact, it is an essential step in optimizing the appliance’s operation and, in some locations, a requirement for meeting the local building code.
A dishwasher air gap is a valve that prevents contaminated water from flowing back into the dishwasher. It creates a literal gap of air between wastewater and fresh potable water.
One end of the air gap attaches to the dishwasher, while the other connects to the garbage disposal or waste line. The top of the air gap, which typically has a decorative covering, sits strategically above the counter. The covering has vents to allow backflow to drain rather than return to the dishwasher. Water draining through the air gap means there could be a clog in the air gap or an issue elsewhere in the dishwasher’s drainage system.
Air gap installation may not be hard, but you need to do a little prep work based on your kitchen setup. Gather your supplies, which could include the dishwasher air gap, hose or tubing, a screwdriver, stainless steel hose clamps, and wrench.
Next, determine proper placement. The air gap must be placed above the dishwasher for air and gravity to do their work. Consequently, the air gap is usually installed on the countertop, either near or as part of the kitchen sink. It should be placed close enough to the sink that any water draining through the air gap vents goes into the sink rather than the counter.
Air gaps are simple devices that rely on basic physics to prevent backflow. They are placed at cross connections, points where wastewater can come into contact with potable water. Do not run your dishwasher until you have completed all of the following steps.
Most countertops and sinks have a precut hole for the air gap with a flat cover over top; however, it is possible that your countertop or sink does not have one. If that is the case, tape off the counter around the area where you want to make the hole, in order to protect the countertop from scratches.
Check the manufacturer’s instructions for the hole size needed to fit the air gap. Then, create a hole using a drill fitted with a properly sized paddle bit or another bit designed for your countertop material. Place the hole close to the sink’s rim so any draining water flows into the sink. Keep in mind that some countertops, like marble or granite, may require contacting a local plumber or contractor to drill through the countertop for air gap installation.
From underneath the countertop, connect the ⅝-inch inlet (the smaller leg) of the air gap to the dishwasher’s ⅝-inch drain hose. Secure the connection with a stainless steel hose clamp or plumber’s tape.
Measure the distance from the air gap to either the waste line of the sink or the garbage disposal. Cut a length of tubing to this length. Note that most dishwasher air gaps have a ⅞-inch outlet, so you would need ⅞-inch tubing.
Attach the outlet (the ⅞-inch leg of the air gap) to one end of the tubing, and secure it with a stainless steel hose clamp. Attach the other end of the tubing to either the waste line of your sink or to the garbage disposal. Secure the connection with a stainless steel hose clamp.
If your garbage disposal has not previously been attached to an air gap, you may need to remove a metal plug inside the tube where the air gap’s tubing connects to the disposal. Then, proceed by attaching the hose to the garbage disposal and securing the connection with a stainless steel hose clamp.
If you have not done so already, remove the vanity cover from the air gap. Push the air gap through the hole in the countertop. Check the manufacturer’s instructions, as there may be a piece that adjusts the fit of the air gap in the countertop. Tighten the retainer nut on the underside of the air gap. You might need an assistant to hold the air gap if it spins while you tighten the nut. Tighten by hand before using a wrench to secure the connection.
Check all of the hose connections to ensure they are secure. Each of these connections is a place for a potential leak. Replace the vanity cover over the top of the air gap. You may need a screwdriver to attach the vanity cover, depending on the design.
Run a complete dishwasher cycle. Check the air gap for leaks on top of and underneath the countertop. Make adjustments as needed.
Over time, dishwasher air gaps can get clogged with debris, slowly reducing flow through the valve. Watch for signs of a growing clog, which could include slow draining from the sink, water pooling around the air gap, and bad odors in the dishwasher. If you notice any of these signs, a simple cleaning often fixes the problem. You can clean the air gap by:
Gently removing the vanity cover, which may require loosening screws depending on the design.
Wipe away surface debris or use a soft brush or bottle brush to remove stubborn debris. You may also want to cover the brush in an all-purpose cleaner before scrubbing the air gap for added cleansing power.
If needed, disconnect the air gap and soak in a solution that is equal parts water and vinegar to remove mineral deposits.
Use a pipe cleaner to remove clogs within the air gap.
Finally, rinse and run water through the air gap to wash off any cleaners or solutions.
Reinstall the air gap if you removed it for cleaning. Put the vanity cover back on.
Installing a dishwasher air gap is not a difficult or lengthy process. Most people can do it even if they lack DIY experience. It requires simple tools (a wrench and screwdriver) and minimal supplies.
You might need to call in a local plumber or contractor if you have to cut a hole in a delicate countertop or if you have a more serious dishwasher clog that is unrelated to the air gap. If the air gap is part of installing a new dishwasher, a pro can do the air gap installation alongside the dishwasher installation. Keep in mind that, including the cost of the dishwasher, pro dishwasher installation costs between $1,000 to $1,500.
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