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Sewage Backflow Valve and How it Works

What is backflow?

Backflow is the unwanted water that makes its way into your home’s water pipes. This usually happens due to heavy rainfall that can cause water to overflow in the city or town’s main sewage system which causes the water to start flowing in the opposite direction. Normal plumbing allows water from homes to drain into the sewage pipeline of the town but backflow is the complete opposite of that. Other reasons for backflow include having drains in your house that are not above the nearest upstream manhole. The risk also increases if you live in a basement or if you have a basement in your house.

What is a sewage backflow valve?

A sewage backflow valve in Toronto is a valve that you can install in the main pipelines of your house. This valve allows water to only flow in one direction, thus stopping the dirty water from coming into the pipelines of the house.

These valves can either be installed at the time of construction which will obviously cost less. Installing the valves after construction will give you a heavy bill as concrete has to be removed to get to the main sewage pipes of the building.

How does the backflow valve work?

The backwater valve has a clear access box through which you can check whether the valve is actually working or not. The valve itself consists of a small flap that is normally open to allow water from your house to exit into the sewer. On either side of this, there is a floatation device that comes into play. When the water starts flowing in the opposite direction, these floatation devices cause the flap to lift and close so that the contaminated water cannot enter your pipes. When the water stops flowing in the opposite direction, the flap falls back into its initial position with the help of gravity and water flow goes back to normal. This is the basic structure of all backflow valves, however, there are different kinds available:

  1. Sewer Check Valve

This is the least expensive and therefore is used the most. It does not prevent backflow completely and should only be used for less than a day.

  1. Manual Sewer Gate Valve

This valve has to be opened and closed manually, so needs a person to be vigilant of the water situation around them to act effectively.

  1. Automatic Flood Gate Valve

This is the most efficient, stopping backflow 100%. This is the most sophisticated device and prevents backflow by completely blocking the path of the water. It can be used for a length of the period as the stainless steel structure is nor easily damaged.


These valves have moving structures that can be damaged so maintenance is key to having these valves work perfectly. Always hire a person specialized in the field when getting these valves checked. The parts should be checked periodically and it should be made sure that they are functioning perfectly so that you are not put in a very difficult situation at the time of need.