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Do I Need an Air Gap for a Washing Machine?

Steven Symes

An air gap device helps you keep the water pipes connected to your washing machine clean.

Without an air gap, a washing machine's dirty water may back-flow.

Having an air gap gives you peace of mind, knowing that your plumbing’s water pipes are protected from contaminants, but ultimately you may be required to have an air gap installed on your washing machine whether or not you want to.

Air Gap Location

A washing machine’s air gap is a small, cylindrical, metal device that sits on the washer’s water supply line. Generally, the air gap sits in the middle of the supply line, but you may find that your washing machine’s air gap sits where the water lines connect to the washing machine, called the inlet holes. The air gap integrates with the water supply line.

Air Gap Purpose

The air gap on any plumbing device, whether it is a washing machine’s water line or an outdoor faucet, is intended to keep your home's water system pure. The air gap prevents water that is contaminated from being siphoned back into your water supply, where the contaminated water can corrupt more water. The air gap creates a barrier to stop siphon forces. In a washing machine’s water supply line, this means water that has flown through the air gap can only flow toward the washing machine.

Siphoning Consequences

If water siphons from a plumbing fixture like your washing machine and back-flows into the water supply pipes, the result may be very serious. When you first start up a washing machine, the clothes and the water inside the tub may have debris and even bacteria in them. If the water inside the washing machine, along with the bacteria, flows back into the water supply pipes, a portion or your home's plumbing system may be a breeding ground for bacteria. The contaminated water may even flow into public water pipes, contaminating the water supply of numerous homes or businesses.

Local Codes

Whether you want an air gap in your washing machine’s drain line may not matter if your local plumbing codes require that an air gap be installed. If you are unsure what the code requirements for washing machines and other plumbing fixtures are, contact your municipal or county officials for additional information and guidance on code compliance. Plumbing codes exist to keep your plumbing system clean and safe for anyone using it and the public at large.