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What Is a Backflow Preventer?

backflow preventor
Your potable water supply comes from the city’s water main. However, water that fills your fire protection system comes from the same source, and it’s not safe to drink. To prevent these two types of water from mixing, authorities demand that homeowners install a backflow preventer. But what is a backflow preventer, and how does it work?
In this article, we’ll cover the basics of a backflow prevention device and the reasons why you need one.

How Does a Backflow Preventer Work?

Before we explain how backflow prevention works, let’s first establish why backflow is a serious issue. In wet fire protection systems, a large amount of water remains stagnant until it starts flowing from a broken sprinkler pipe or sprinkler head. Over time, bacteria festers in stagnant water, transforming it into a smelly, thick sludge that can trigger severe health problems if it reverses into the city’s potable supply.
This is where a backflow prevention device comes into play. It’s a simple yet ingenious system that mimics how the human heart works. In other words, it allows water to flow in one direction and closes if pressure comes back in the same direction.

Backflow prevention closely resembles this mechanism. It siphons water through a branch line after you flush your toilet or turn on your kitchen faucet. During the process, the water transports any other substances in the pipe.

For instance, sprinkler systems may contain weed killer, fertilizer, and other toxic items. Without a backflow preventer on the cut-in of your sprinklers, the water system can contaminate your water supply with numerous toxins.
While all backflow preventers work according to the same principles, there are some differences between various types of backflow prevention devices. Here are the most common models:

Double-Check Valves

Double-check valves keep toxic substances away from the potable water in your lines. As the name suggests, it features two check valves that close to prevent the adverse effects of drastic fluctuations in your water pressure. Plus, the second check valve can be activated if the first becomes stuck.
This type of assembly typically comes with two ball valves for confinement and troubleshooting. It can also be installed with backflow test cocks to enable the plumber to connect their test equipment and check if the system works correctly. In most cases, double-check valves are used to fend off water contamination in boiler, lawn, and fire systems.

Reduced Pressure Zones

Like double-check backflow preventers, reduced pressure zones also feature two check valves. The biggest difference is that reduced pressure zones have a relief valve that opens to release toxic water. If the valve flushes water from the lines, it indicates damage on your check valves or the main water pipe. But once a trained plumber fixes the system, the valve stops draining water.
Reduced pressure zones are common in suburbs and cities. They effectively keep fertilizers, pesticides, and other toxic chemicals from polluting sanitary water.

Pressure Vacuum Breakers

Many lawn systems come with pressure vacuum breakers. They’re easy to assemble or disassemble on properties of all sizes. This valve type can be mounted near an exterior wall or inside your recessed underground box.
Pressure vacuum breakers prevent dirty sprinkler water from reaching your drinking water. If you can’t find it outside your house, check your basement. It might be installed in this area or your utility closet.

How Do I Know I Need a Backflow Preventer?

Homeowners who haven’t installed a backflow prevention device are likely to experience some of the following issues:

Lower Water Pressure

Water pressure can drop throughout your house, including your kitchen faucet, showerheads, and bathroom sinks. It usually indicates backflow that creates a vacuum-like effect in the plumbing system that keeps water from flowing at the optimal rate. Over time, this can turn into a more serious problem, such as burst pipes.

Poor Water Quality

If the water in your home tastes odd, it almost always points to backflow. It means your water isn’t safe for drinking and other types of consumption because it’s contaminated. Left unchecked, your water will retain its strange taste that often resembles sulphur.
Drinking low-quality water can trigger many symptoms, such as diarrhea and vomiting. To avoid this scenario, reach out to a licensed plumber to install backflow preventions.

Water Discoloration

Besides the sulphur-like taste, water can also be discoloured due to backflow. Contaminated water generally comes out yellow, brown, or pink.
If you notice your water has changed colour, consider it an emergency. Contact a plumber to inspect the system right away and determine if you need a backflow preventer.


Leaks can be a sign of several plumbing problems. In many cases, they indicate minor issues, such as small bursts or a breakage. But sometimes, they also point to backflow, especially if they’re recurrent.
To diagnose the problem, hire a professional plumber. Even if you’re not facing backflow, they’ll fix the leak and restore your plumbing to its former condition.

Strange Smell

An unpleasant smell is another potential indicator of water contaminated by backflow. It typically occurs when turning your faucet on as it builds up in your pipes and is released when water starts flowing. Once it’s out of your faucet, it usually smells like sulphur.
In most cases, the odour can be attributed to poor drainage. But on occasion, it can be caused by backflow, which requires immediate attention.
installed flapper backwater valve

Visible Particles

Both your working and drinking water should contain no rust particles, sediments, or mineral deposits. Over time, they can develop due to inadequate filtration, but they can also be brought about by backflow. Consequently, your water is no longer safe to use, and the plumbing system requires a backflow prevention device.

What Is a Backflow Preventer? It’s a Must-Have for Your House

Leaving your plumbing system without backflow prevention is a risk you can’t afford. It can contaminate your water supply and lead to severe health issues.
For top-rated backflow prevention device installation in your Toronto home, reach out to MT Drains & Plumbing. We can install this much-needed component quickly and efficiently while preserving the integrity of your plumbing. The result will be an effective backflow preventer that will serve you for many years to come.

Paul S

Paul has more then 20 years in basement waterproofing and plumbing projects experience. Looking for an advice from an expert plumber? Make sure to read Paul's articles about residential waterproofing and plumbing projects in Toronto.

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