Air Gaps and Dishwasher Backflow: Is Your System Safe?
Modern dishwashers offer convenience and sanitation—but without proper safeguards, they can also create risks for your home’s plumbing system. One commonly overlooked issue is backflow, the reversal of dirty water into the clean water supply. The unsung hero in this situation? The air gap.
At Brown Plumbing & Heating, we get a lot of questions from Billings and Laurel homeowners about air gaps, dishwasher drains, and whether their kitchen setup meets code. Here’s what you need to know about protecting your dishwasher—and your family—from unsafe water.
What Is Backflow and Why Is It a Problem?
Backflow occurs when contaminated water flows in the reverse direction, potentially entering the clean water supply. In the case of a dishwasher, this could mean dirty dishwater—loaded with food particles, grease, and bacteria—getting siphoned back into your sink or supply line.
Backflow can happen when there’s a sudden change in water pressure, such as during a water main break or heavy system use. Without the right plumbing safeguards, your kitchen could unknowingly become a backflow risk.
What Is an Air Gap?
An air gap is a simple but effective device that prevents backflow. It’s usually a small cylinder mounted next to the kitchen faucet and connected to the dishwasher drain line.
Here’s how it works:
Dirty water from the dishwasher travels to the air gap.
The air gap creates a physical space between the dirty and clean water systems.
If a clog or backup happens, water spills into the sink instead of flowing backward into the dishwasher or supply lines.
Air gaps are required by plumbing code in many states, including Montana, because they provide the most reliable form of backflow prevention.
Signs Your Dishwasher May Not Be Protected
Many homeowners—especially those with older kitchens or DIY remodels—don’t realize they’re missing a backflow safeguard. Look out for these signs:
No visible air gap next to the faucet
Gurgling or bubbling noises during the dishwasher cycle
Water backing up into the sink or dishwasher
Dishwasher smells even after cleaning
In some setups, homeowners use a high loop in the drain hose as a workaround. While this method is better than nothing, it’s not as effective—or as code-compliant—as a true air gap.
Is an Air Gap Required in Montana?
Yes. According to current plumbing codes, an air gap is considered the safest and most reliable way to prevent backflow from a dishwasher. Many city inspectors in Billings and Laurel will flag missing air gaps during kitchen remodel inspections or home sales.
Even if your home predates these requirements, retrofitting an air gap is a smart and affordable upgrade.
How to Check (and Fix) Your Dishwasher Setup
Not sure if your dishwasher has an air gap or if it’s working properly? Here’s what to do:
Look next to the faucet for a small metal or plastic cap (that’s your air gap).
Listen during a cycle—if you hear gurgling or see water overflowing, the air gap may be clogged.
Call a licensed plumber to inspect your dishwasher’s drainage line if anything seems off.
At Brown Plumbing & Heating, we offer quick inspections and air gap installations for peace of mind. Whether you’re updating your kitchen or just want to ensure your system is safe, we’re here to help.
Protect Your Kitchen—and Your Water Supply
In a place like Montana, where we value clean, dependable water, a simple air gap is an important line of defense. Don’t wait until a plumbing emergency—or a failed inspection—reveals a preventable risk.
📞 Schedule your dishwasher drainage check today with Brown Plumbing & Heating at (406) 656-8585 or visit https://brownplbg.com. Proudly serving homeowners in Billings, Laurel, and surrounding areas.
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