If you own a business or commercial building, you’re likely familiar with the plumbing concept of backflow prevention. After all, it’s a requirement for most commercial facilities in our area. However, homes aren’t subject to the same regulations. Only a few situations make backflow prevention a requirement in residential settings. Nevertheless, it’s a good idea to understand the concept of backflow prevention and when it’s necessary.
What is Plumbing Backflow?
Backflow refers to water flowing in the opposite direction than intended. More specifically, it describes water flowing in the wrong direction inside potable water supply lines. When backflow happens, it risks contaminating your potable water supply. That’s especially true when a potable water supply line comes in contact with greywater or blackwater. Worse still, backflow from a single home can contaminate the water in surrounding buildings. In extreme cases, backflow can adversely affect an entire water supply system.
What Causes Backflow?
There are two principal causes of backflow issues in plumbing. One is called backpressure. This refers to a situation where the pressure in your home’s plumbing exceeds incoming pressure. In homes, backpressure can happen when various water appliances over-pressurize supply lines. For example, a tank-style water heater creates pressure in your supply lines. Ordinarily, that pressure doesn’t exceed your incoming supply pressure. However, a malfunction can quickly change that. When one occurs, the pressurized water in your home’s plumbing reverses direction and flows into the water delivery infrastructure. Backpressure can also happen in sewer and septic system lines. In that case, however, the backflow goes in the opposite direction, sending contaminated water into your home.
The other cause of backflow is called back siphonage. It’s the result of external forces that lead to drops in your incoming water pressure. For example, a broken water main in your municipal water system could produce a rapid pressure drop. Also, nearby fire hydrants can quickly take large amounts of water. Those situations create a pressure differential that draws water out of your plumbing and into surrounding supply lines.
Types of Backflow Prevention
You can build backflow prevention into a plumbing system in a few ways.
Air Gap
An air gap is the most common type of backflow prevention. Most plumbing fixtures in your home use it as their primary backflow prevention measure. Air gaps create a physical separation between a potable water outlet and a contamination source. The easiest way to see it in practice is by looking at one of your home’s tubs. You’ll note that the water spout for your tub is several inches above the top edge of the tub itself. That creates an air gap between a potentially contaminated water source and your potable water supply. For example, if your tub drain backs up, the tub would overflow before contaminated water could reach the spout. Air gap protection is also inside dishwashers, washing machines, and toilets. However, it’s inside the respective device mechanisms, so you can’t readily see it.
Atmospheric Vacuum Breaker
An atmospheric vacuum breaker (AVB) is a device that uses an air inlet and stopper mechanism to prevent backflow. When water runs through and AVB in the expected direction, it forces the stopper up and into the air inlet. That lets water flow through the device without leakage through the inlet. When water pressure falls, negative pressure and gravity force the stopper downward. That seals the incoming supply line and opens the air inlet. The air inlet prevents a vacuum from forming due to the pressure loss, maintaining equilibrium in the pipes.
Pressure Vacuum Breaker
A pressure vacuum breaker (PVB) is all but identical to an AVB, with one mechanical difference. A PVB features a spring-loaded stopper. That makes PVBs more reliable and suitable for a wider variety of applications. PVBs may also feature pressure gauges that make periodic functionality testing possible.
Double Check Valve
A double check valve (DCV) features two spring-loaded valves to serve as redundant backups. In the event a single valve fails, the other still prevents backflow. Plus, when both operate normally, you’re assured a tighter seal due to a distributed pressure load.
Reduced Pressure Zone Device
Finally, a reduced pressure zone device (RPZD) hybridizes the previous mechanisms. It features two independent spring-loaded check valves with a monitored zone in between. The middle zone also features a pressure-release valve as a final roadblock to backflow. In an RPZD, the check valves can work in concert or independently. That provides redundancy, just like a double check valve. However, the pressure relief valve in the middle can still prevent backflow even if both check valves fail.
Where Your Home May Need Backflow Protection
A few parts of your home’s plumbing may require backflow prevention. One situation where it’s a must is if you have a sprinkler system for your home’s landscaping. That’s because damage to a sprinkler head or water line could allow foreign matter into your supply lines. To avoid that, you must install an inline backflow prevention device in your irrigation system. Depending on the type of backflow prevention device, it may require installation either above or below grade.
Another place where you might want a backflow prevention device is on your home’s hose bibs. You can install a permanent backflow prevention device on the water line that serves each hose bib. Alternatively, you can install a screw-on vacuum breaker between each bib and an attached garden hose. Either method prevents contamination from entering the line, even if you leave your hose in the dirt.
You may also want backflow prevention installed on your home’s sewer line. A backflow prevention valve is essential if your home has a septic system. If your septic tank backs up, it will keep sewage from reentering your home. That can prevent significant damage to your home and help you avoid an unsanitary mess. If your home relies on a connection to a public sewer system, you may also want backflow prevention. It can keep your home safe when municipal sewer lines become overwhelmed during storms.
Finally, you need backflow prevention if your home has a boiler or other hydronic heating system. In that case, the backflow preventer would keep water circulating through your heating system separate from your potable water.
Your Backflow Prevention Experts
Since 1975, Level 9 Heating, Cooling, and Plumbing has offered backflow prevention and plumbing solutions in St. Louis, MO. We also provide leak detection, water heaters, and drain cleaning. Plus, we offer complete residential and commercial HVAC and indoor air quality services. You can count on us to answer our phones 24/7 and always treat you and your property respectfully. Our plumbers and HVAC technicians undergo continual training to stay at the top of their game. As a business, we’re also active community members. We donate our time, skills, and funds to worthwhile local organizations. We’re also Better Business Bureau accredited with an A+ rating. So, if you need backflow prevention in St. Louis, call our team of experts at Level 9 Heating, Cooling, and Plumbing immediately! We offer a comprehensive maintenance plan to meet all your needs!
