What Is A Backflow Prevention Device?

May 18, 2022

Water flowing back towards the water meter should be a significant concern for any home/business owner. But such a situation should never happen. Enter backflow prevention devices, also known as backflow preventers.

A backflow preventer is a piece of equipment designed and installed to prevent contaminants from impacting potable water supplies. There is a good reason you should care about backflow prevention. A backflow can pollute your drinking water, compromising your family’s health safety. It could also mean legal liabilities for your business or commercial property investment. 

So, what do backflow preventers look like? Are they available in different types? How much do plumbers charge to install them? 

Well, join the team at Gallegos Plumbing, your trusted plumbing service provider in Ventura, CA as we explore the above questions and more.

What is backflow?

Backflow is the undesirable water flow direction. 

Normally, clean water from the main supply should flow into your home. But when the direction reverses, freshwater mixes with wastewater. Subsequently, your drinking water becomes contaminated with harmful substances (including human waste, fertilizers, and pesticides), increasing the risk of severe health issues.

Possible signs of backflow include discolored water, water leaks, and slow drainage.

How does backflow occur?

Backflow stems from a pressure difference between two points in a plumbing system. The primary culprits are back-siphonage and backpressure.

Back siphonage is a negative-pressure situation where the downstream (customer’s) water pressure drops below the public supply main’s. The pressure difference could draw contaminated water into the public distribution system. Causes of back-siphonage include:

  • Stoppage of main water supply
  • Increased demand at one location
  • Undersized pipes

Backpressure is a positive-pressure condition that occurs when the pressure in a customer’s plumbing system exceeds the water supply pressure. In this case, downstream pollutants are pushed into the freshwater supply. Your plumbing system could experience increased pressures from, but not limited to, pumps, elevated tanks, recirculating systems, or boilers. 

In either case, a backflow preventer for residential or commercial settings suffices to isolate possible contaminants from the potable water supply.

What is a backflow prevention device?

As its name suggests, a backflow prevention device ensures water flows in the intended direction. It springs into action when pressure changes between the consumer side and main supply, effectively preventing the reversal in direction and potential contamination of potable water. Generally, backflow preventers for residential use are smaller than their commercial counterparts. 

But what does a backflow preventer look like? The device is easily noticeable as equipment with several ports (test cocks) and 1-2 caps on a chamber lying between two shutoff valves. 

Where is the backflow preventer located? 

These safety devices are typically installed on the mainline directly after the water meter. Plumbers also install backflow preventers inside the irrigation box. 

The type of backflow prevention device installed on your property will primarily depend on the hydraulic conditions and degree of hazard. It is a good idea to have a professional plumbing services contractor assess these criteria and install the device to code. 

Backflow prevention device types

There are three primary types of backflow preventers: 

  • Reduced-Pressure Zone Device (RPZ):  RPZ takes the cake for the most complicated and expensive yet most reliable and secure backflow prevention device type. It comprises a pressure differential relief valve between two spring-loaded check valves. 
  • Double Check Valve Assembly (DCV): DCV comprises two independently operating check valves and four test cocks between two shutoff valves. One check valve should close off during a backflow, while the other serves as a backup. DCVs are the preferred choice for indoor or underground installations. 
  • Pressure Vacuum Breaker (PVB): Among the most prevalent type of backflow prevention devices, PVB is an elbow-shaped device consisting of a loaded check valve and a loaded air inlet valve between two shutoff valves. It’s affordable and easy to install and service. It only prevents back-siphonage, therefore not allowed where backpressure is a likely hazard. 

How does a backflow preventer work?

The backflow preventer chamber houses the device’s workhorses: the check valves. These are spring-loaded flaps/discs designed to open when water flows in the intended direction and close when the flow direction reverses. 

A reduced pressure zone device has an additional valve known as a pressure differential valve. The water pressure difference in the two tubes serving this valve determines its open or closed status. The valve stays closed if the water pressure is even in both lines. It opens when one pipe experiences a higher pressure than the other, allowing water to drain out through an outflow pipe. That way, the high-pressure backflow will not break through check valves. 

Is a backflow preventer required by code?

Yes. It is mandatory to install a backflow prevention device in commercial and industrial property. Residential properties eligible for these valves are those with: 

  • Three floors and above
  • An irrigation system
  • A water meter that’s at least 1’’ in diameter
  • A fire sprinkler system
  • An auxiliary water system

The law also stipulates property owners to have their backflow preventer valves tested annually by a licensed plumbing services provider. 

Our plumbers at Gallegos Plumbing conduct are pros at installing, repairing, and maintaining backflow preventers. We also handle all the paperwork associated with the yearly tests.

How much does a backflow prevention device cost?

Backflow prevention device costs typically range between $35 and $600. But also available is a backflow preventer at Home Depot that could set you back as much as $836. 

California plumbers charge between $100 and $400 to install a backflow preventer valve. That amounts to $135-$1,000 in typical total costs. Please note that a permit could add at least $50 more to the installation price tag. 

Bottom Line

In the end, choosing and installing a backflow prevention device is all about your needs. Work with a professional plumber to help you weigh the options and comply with the local plumbing codes. 

For more information or a consultation on a plumbing installation, repair, or maintenance consultation, reach out to Gallegos Plumbing. We are a licensed, insured, and bonded contractor providing top-level plumbing services across Ventura County at pocket-friendly prices. Plus, our plumbers are experts in all brands and types of backflow preventers, residential, industrial, and commercial. Call us today at 805-750-1830 to schedule an appointment. 

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Andi Perullo de Ledesma

I am Andi Perullo de Ledesma, a Chinese Medicine Doctor and Travel Photojournalist in Charlotte, NC. I am also wife to Lucas and mother to Joaquín. Follow us as we explore life and the world one beautiful adventure at a time.

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