How to Install a Backwater Valve

Lead Image for How to Install a Backwater Valve
  • 10-20 hours
  • Advanced
  • 50-500
What You'll Need
Jackhammer (optional)
Sewer pipe
Backwater valve
Concrete (optional)
What You'll Need
Jackhammer (optional)
Sewer pipe
Backwater valve
Concrete (optional)

Unless you live in a pretty rural area, your home is probably connected to a sewer system. And if you've ever had one, you know that a sewer backup is positively horrible. Not only are sewer gases foul-smelling, but they are also actually toxic. Backwater valves are prevention devices that prevent sewer backups that can cause human waste to pour out of your toilets and drains. Knowing how to install a backwater valve will keep you much safer.

When You Need a Backwater Valve

Clearly, backwater valves are beneficial devices. But they are only necessary sometimes. Do you have any need for a backwater valve? To answer the question, you'll have to examine the positioning of your home and its sewer line.

Locate the maintenance hole cover for the sewer, which should not be more than a few feet in either direction leading away from your home and will most likely be very close to the street on either side. Stand on the maintenance hole cover, if you can. Now, look at your home. Is your home sitting on a hill or a grade that positions your home's foundation higher than the maintenance hole cover? If your home's foundation sits at a higher grade, a backwater valve isn't at all necessary and won't have any effect.

If your home sits at relatively the same grade or sits lower than the maintenance hole cover, a backwater valve is a really good idea and will help prevent waste from flooding your home. Now, you need to focus on installing it!

pvc backwater valve pipe connection


Installing a backwater valve is a pretty serious DIY project. Wear the proper protective gear, such as eye protection, and take the time to complete every step well and correctly. Don't try to take any shortcuts. You need to locate the main shut-off valve to your home first. This may be by the water meter. Turn off all the water to your home and caution everyone inside not to use the drains or flush the toilets.

Step 1 - Pick a Spot

Locate the right spot to place your backwater valve. Typically, this will be an area prone to flooding, where water collects. You cannot simply pick a spot. This is a spot you will find along the existing sewer line that goes into your home. Past a certain point, the sewer line is municipal property and not yours. This spot may be in the basement if you have one, in which case you will need to destroy part of the floor to achieve your goal. If the floor is concrete, this will require a jackhammer.

Step 2 - Dig Out the Line

Dig out a hole around the sewer line. The hole needs to be big enough to hold the backwater value. The specific dimensions of the valve will be included in the box when you purchase it. The hole needs to be both as wide and as deep as the valve.

Step 3 - Dig Even More

Dig out an area around the sewer line where you will be installing the backwater valve. You will need enough space to work in, as well as room to install new piping and the valve itself.

hand reaching into trench around drainage pipe

Step 4 - Cut and Insert

Cut out a section of the sewer pipe big enough for the backwater valve. You will place the backwater valve in the pipe and then replace the sewer pipe around the valve. You may also need to install extra piping to create enough space for the backwater valve. Add couplings as needed to connect pieces of pipe.

Step 5 - Fill the Hole

Use gravel and dirt to fill up the holes you dug and make the plumbing stable.

Step 6 - Replant

Add grass seed. This is best done in the spring, but it can help those who have just dug up some of their lawn, too. You might need to refill a hole with concrete if you had to dig in your basement.

Maintenance and Care

Check your backwater valve every six months to keep it in good working order. If you have sewer backup problems, check it even more often.