How to Maintain your Backflow Valve

Have you ever wondered what happens in your home when the city sewer system overloads and starts to back up? Ever wondered what protects your home from a sewage disaster?

I would be willing to bet that the majority of people reading this are unaware of the little piece of plastic that’s protecting them from just such a disaster. It’s a backflow valve installed under your basement floor and has been recommended in Edmonton homes since the early 90’s. If your home was built prior to 1990 it’s likely that you don’t have one unless either you or a previous owner had one installed.

The reality is that unless you’re a plumber, an insurance agent or a builder, you’re not likely aware of how important that little piece of plastic is. And more importantly, you may not be aware that you need to maintain that piece of plastic or your insurance won’t cover you in case of a sewer back up. That’s right – even if you have a backflow valve installed in your home, if you haven’t done basic maintenance on it, your insurance won’t likely cover you. I suggest double checking with your insurance provider on that!

Here's a simple diagram to show how a backflow valve works:

Backwater valve diagram

But there’s good news…maintaining a backflow valve is one of the easiest tasks to do in your home. Follow these easy steps to check it and you can rest assured that it’ll be in good working order if it’s called upon to protect you.

1. Locate the cover panel: Here’s a picture of what the cover panel looks like. Most of the homes that I’ve inspected that have been built since the 90’s have a cover just like this one. The problem with many homes is that the cover panel may be covered with flooring. If your basement is carpeted, then you should be able to feel it. It’s most likely near the basement wall nearest to the street, or in the utility area near the floor drain or sump pump. If you have a solid surface such as laminate or tile, it will be difficult to find.

Backflow valve access panel

2. Remove the cover. Once you’ve removed the screws and lifted the cover you’ll either see the backflow valve unit…or you’ll see dirt. Some builders covered the valve unit with dirt to protect it during the construction process. Once you’ve removed the dirt, you don’t need to put it back in.

3. Remove the cap. Once the access cover is removed, you’ll see a black plastic (ABS) drain pipe. It will have a 4-inch circular cap. They’re usually pretty tight, so you may need a wrench to unscrew it (counter clockwise).

Backflow valve unit

4. Check the gate. Find and lift the gate to ensure that it closes completely and you’re done! Screw the cap back on (tight!) and put the access cover back on.

valve gate


This simple process should be done on an annual basis. You can do it while you’re draining your water heater and testing your sump pump. Those procedures can be found on my blogs from December 24/15 and July 11/16 respectively. For a good video on backflow valves check out this link to a video posted by a plumbing company in Toronto. And by all means, if you have any questions, please feel free to call Fortified Home Inspections at 780-919-9464!

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