The Difference Between a Backwater Valve and a Backflow Prevention Valve

The Difference Between a Backwater Valve and a Backflow Prevention Valve

Many regions and cities have policies regarding backflow prevention valves, or backflow preventers, as they are also commonly known. But what is a backflow preventer and is it different from a backwater valve? Here’s everything you need to know about backflow valves and some helpful information on whether you need them.


What is Backflow?

Backflow is simply water flowing through a pipe in the opposite direction than it is intended to.

For example, sewage systems are designed to transport sewage away from a property and into the public sewage system, but it is possible for dirty water or sewage to travel back up a feeder sewage line and back into a property.

This would be the most common example of backflow, but there are other cases of backflow where water is travelling in the opposite direction than is intended.


What is a Backwater Value?

A backwater valve is a device installed on the sewage line where your sewage line connects to the city sewage line. Your sewage line transports dirty water from your property to the public sewage system, and a backwater valve prevents dirty water or sewage from coming back up your line.

Sewage backflow can happen if the city sewage systems gets overloaded. If there is a major storm or a quick spring melt, for example, the city sewer systems can become overloaded with more water than they’re able to handle properly. The result can be that dirty water starts pushing back up the sewage lines into properties, possibly resulting in dirty water coming up through your basement floor drains, shower drains or toilets.

Another cause can be a blocked city sewage line. If a portion of the line becomes overloaded and fills up from all the feed lines, dirty water can start backing up into those feed lines.

A backwater valve monitors the flow direction on your sewage line and if it senses a reverse in flow from the normal direction it closes. This stops dirty sewage water from travelling back up your sewage line and into your property.


What is a Backflow Prevention Valve?

Although similarly named to a backwater valve and often used interchangeably, a backflow prevention valve is very different from a backwater valve.

As backwater valves protect your sewage line, a backflow preventer is installed on and protects the clean water supply line. It is possible that water can be forced into the city clean supply line from a property. If this water is dirty or non-potable, then this can lead to a potentially dangerous contamination of the city’s clean water supply.

A backflow prevention valve stops water from leaving your property plumbing system and entering the public clean water supply.

So, the difference between a backwater valve and a backflow prevention valve is that one stops sewer water from entering your system (the backwater valve) and one stops water from entering the city’s clean water supply (backflow prevention valve).


Do You Need a Backwater Valve or a Backflow Prevention Valve on Your Property?

The requirements for backwater valves and backflow prevention valves vary from one municipality to another – some require them while others only recommend them.

At the time this article was written there were no municipal requirements for backwater valves, it is completely at the discretion of the property owner or manager. Some insurance companies offer discounts or rebates for properties with backwater valves, but backwater valves are not required.

Requirements are different for backflow prevention valves. In the City of Toronto and Halton Region, every commercial building and newly built homes are required to have backflow prevention valves. Older homes will eventually be required to have backflow preventers installed once the resources become available to support the annual testing requirements.

The Region of Peel is more lenient, only requiring certain types of facilities to have backflow prevention valves installed – those that deal with harsh or dangerous chemicals like hospitals, funeral homes and certain types of industrial facilities.

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