Backflow: The Enemy of Your Plumbing System

When you think of plumbing problems, you probably think of leaks or clogged drains. It's just a bunch of pipes, after all. What's the worst that could happen? Backflow. Backflow might be the worst thing.

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Backflow in your plumbing system is something that might not be on your radar, but it's a potentially dangerous situation that can contaminate your water supply. Learn what backflow is and how you can prevent it to keep your family safe.

What Is Backflow in Plumbing?

When everything works correctly, the water flows through your plumbing system in one direction. It enters your home, goes through your pipes and flows out through your sewer system. Backflow happens when the water flows the opposite direction. Instead of flowing out of your home, the dirty wastewater flows back into the pipes inside your house.

Backflow can happen at different points in your plumbing system. For instance, the dirty water draining from your dishwasher could flow back into your clean water line if there's an issue with the connection. A broken water main can cause backflow throughout the system.

There are two main types of backflow. Back siphonage is caused by negative pressure in your system. Instead of a consistent pressure that keeps the water flowing in one way, the negative pressure causes it to flow backward. You can think of the negative pressure as sucking the water back the incorrect way within the system.

Back pressure happens when there's too much positive pressure in your wastewater system, causing it to become higher than the pressure on the incoming side. This pushes the water back, rather than sucking it back, in the opposite direction.

What Happens If There Is Backflow?

If backflow happens in your plumbing system, dirty water flows backward in the system. In some cases, it mixes in with your clean water pipes, contaminating your clean water source. That water could contain human waste, soap, food particles, fertilizers or other potentially dangerous contaminants that can make you sick or affect your health. If you consume the contaminated water, you might notice gastrointestinal symptoms, including nausea and diarrhea.

Looking at the signs of backflowing helps you understand what backflow does to your plumbing system. The signs include:

• Discolored water that may appear gray, brown or yellow

• Smelly water, particularly a sulfur smell

• Bad-tasting water

• Visible particles in your water

• Decreased water pressure

• Slow drains

• Gurgling, banging or other strange sounds from your pipes

• Leaks

Why Does My House Have Backflow?

There are several potential causes for backflow in your house. Some common examples include:

• Water main breaks. When there's damage to your home's main water line, the supply line often doesn't have enough pressure to keep water flowing in the correct direction.

• Plumbing damage. Leaks, clogged drains and other issues within your plumbing system can cause backflow.

• Use of fire hydrants. If fire hydrants are used in your neighborhood, that large consumption of water could create backflow in your home.

• Plumbing renovations. While doing work on the plumbing system, changes in water pressure could cause temporary backflow. Professional plumbers should take steps to prevent this issue while they work on your home.

• Pressure issues within your home. Different systems within your home that use water could affect the pressure within the system and cause water to flow the wrong way.

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What Is a Backflow Preventer?

There are several types of backflow preventers, all of which connect to your plumbing system and stop backflow. They only allow the water to flow in one direction, thereby keeping contamination from happening. Each type uses different mechanisms to keep the water moving in only one direction.

How Does a Backflow Preventer Work?

How a backflow preventer works depends on which type you install. Here are some of the options:

• Pressure vacuum breaker. Commonly used with irrigation systems, a pressure vacuum breaker uses a check valve to keep water from backflowing when there's a pressure drop.

• Atmospheric vacuum breaker. Created as a 90-degree angle, this device drops a check valve if the system develops negative pressure and lets air into the system to correct the problem.

• Double-check assembly. If the pressure on the supply side is lower than the pressure in your home, the two check valves close.

• Air gaps. This backflow device is used on dishwashers to prevent the contamination of your drinking water. It adds an air gap between two sections of the drain hose to keep water from flowing the wrong way.

A professional plumber can help decide which type of backflow assembly you need.