Backwater Valves for Sewage Backflow Prevention

By Mike Holmes

Mike’s Advice / Home Safety & Maintenance

Wednesday, April 12th, 2023 @ 3:10pm

How Do You Stop Sewage Backflow?

All the millions of litres of water that come down in precipitation have to go somewhere. Like good urban planners, we have created culverts and drains and sewers that lead to treatment plants or bodies of water. But in the event of excessive rain, all this water creates pressure on the municipal sewage system. This leads to flooding and sewage backups. So how do you prevent sewage backflow?

The simplest thing you can do to keep water out of your basement is to control it at the surface. Surface water, like rain or melting snow, or water from irrigation, is pretty easy to control, compared to water below grade. There’s not much you can do about underground streams, or the water table in your area and the resulting hydrostatic pressure on your foundation. But there is a lot you can do on the surface. That’s where backwater valves for sewage backflow prevention come in. The one I recommend is called Sentinel Drain Guard.


Sentinel What's in the Box

Sentinel Drain Guard-easy to install and protects against sewage backflow

What Is A Backwater Valve?

If you are doing a basement renovation or even just tackling your seasonal maintenance tasks, I highly recommend you install the Sentinel Drain Guard (backwater valve). Some municipalities might even provide subsidies on installing a backwater valve, especially if you live in an area where sewer back up is common. A backwater valve protects you from city sewer back up and you can install this device yourself. 

Sentinel Drain Guard 2

A Drain Guard is a smart and simple product that we have installed on many of my job sites. You do not need a licensed plumber to install this.

If the Sentinel Drain Guard backwater valve detects a backflow of sewage, it switches from an open position to a closed position preventing water from flowing back up your pipes into your basement. When this device is installed in your basement floor drain it will guard against sewage backflow from entering your house causing thousands of dollars in damage and loss of sentimental property. 

I recommend the Sentinel Drain Guard. You can install it yourself. Its sturdy, reliable and comes with a drain cover.

How To Install The Sentinel Drain Guard

The Sentinel Drain Guard is easy to install. First, measure the size of your drain. Is it a 3” or a 4” drain? You will have to remove the old drain cover from floor drain and wipe the throat of the drain pipe clean.

For 3” (75 mm) Drain:

  1. Remove the 3” Device from the 4” Adapter and discard the Adapter
  2. Insert backwater valve device fully into drain pipe opening until the device drain cover is resting on the floor
  3. Secure the Device by fully tightening TWO screws which will splay the expandable rubber side seals against the adjacent drain pipe wall while simultaneously anchoring the Device into place

For 4” (100 mm) Drain:

  1. Seat backwater valve device fully into 4″ Adapter aligning the four screws on the Adapter with the corresponding holes in the Device drain cover
  2. To unitize the Device/ 4″ Adapter Assembly, tighten the TWO screws in the Device snuggly but **DO NOT OVER TIGHTEN**. This will splay the expandable rubber side seals of the Device against the adjacent wall of the Adapter while simultaneously anchoring the Device to the Adapter.
  3. Insert Device/Adapter Assembly fully into the drain pipe opening until the Device/Adapter Assembly drain cover is resting on the floor
  4. Through the holes in the Device/Adapter Assembly drain cover, secure the Assembly by fully tightening the Adapter’s aligned four screws which will splay the Assembly’s expandable rubber side seals against the adjacent drain pipe wall while simultaneously anchoring the Assembly into place

Sentinel Drain Guard Graphic

Basement Flooding Issues

There are lots of reasons you might experience a basement flood: heavy rains, spring run off from a rapid snow melt, a sewage back up, a broken pipe or even a washing machine overflowing.


The amount of water could be minimal and confined to a small area, or it could be several inches deep covering your entire basement. The potential for damage is the same and you need to take it seriously.

Basement flooding can create the perfect environment for mold and poor indoor air quality, putting your family’s health at risk. You will also have to deal with your insurance company, who may or may not cover the water and sewage damage.

Sewer Backup

Damage from a sewage backup can cost you thousands of dollars in damage and will contaminate your basement. Installing a backflow prevention valve is easy and will help prevent flooding. It is inexpensive and homeowners can install it themselves. I really think this is something that should be in every home. Trust me, you don’t want to end up with dirty water in your basement.

Don’t wait until you have a sewer backup into your home. A backwater valve doesn’t cost that much and you can install it yourself. Remember, if you do experience basement flooding, do not rush to rebuild. Here are 12 steps you need to follow after a flood.

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