How to Install a Toilet Flange on a Concrete Floor? – 8 Steps

Written by

Paulk Webb


Freddie J. Hagopian

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how to install a toilet flange on a concrete floor

Are you in the process of installing a toilet flange on concrete or tile, but feeling a bit overwhelmed? No need to worry! We’ve got you covered with this simple and easy-to-follow guide. Installing a toilet flange might sound like a complicated task, but with the right approach, you’ll have it done quickly.

Below, we’’ll show you how to install a toilet flange on a concrete floor, so you can avoid leaks in your toilet. So sit back, relax, and let’s get started!

Steps to Install a Toilet Flange on a Concrete Floor


For toilets with existing flange, you will need to remove the component first before installing a new one. Otherwise, you can skip to step 4 in the installation diagram to see how a toilet flange should be installed.

What to prepare:


  • Putty knife
  • Screwdriver
  • Dremel tool and shop vac (optional)
  • Rotary hammer
  • Masonry or concrete screw
  • Brush and soap
  • Gloves
  • Protection glasses

Step 1: Scrape off the wax seal


After removing the toilet, you may notice something thick and sticky around the toilet hole—this is called a wax seal and is used to secure the toilet. This component should always be removed, as it has lost effectiveness once the toilet is removed.

To scrape this off, you can use a putty knife, and remember to put gloves on to avoid dirt and injury. Make sure to get rid of all of them so that you can attach the new wax ring properly.

Step 2: Remove the old toilet’s flange


As you finish scraping off the wax seal, the first step is to remove the old toilet flange. Unscrew the toilet flange screws, and take them out of the drain pipe’s opening. Then, lift the flange off the waste pipe. If it’s too stubborn, you can pry it out with a putty knife or a screwdriver.

In case the flange bolts are too firmly embedded in the concrete floor, you can use a Dremel tool to cut the flange into smaller pieces. As this process is slightly messy, you’ll need a shop vac to clean the area afterward.

Step 3: Clean the hole’s opening


Next, the area around the hole may need some cleaning. You can clean the area with a brush and soap or a power drill with a brush on top to remove any build-up and rusted dirt around the toilet drain pipe.

And with this, you are ready to start your toilet flange installation!

Step 4: Pick a new flange & a new wax ring


Before setting a toilet flange, you should pick the one that’s most suitable for your toilet. Measure your old toilet’s diameter and get a new one of the same size. Alternatively, you can bring it to a hardware store and ask the salesperson for help.

Another way to pick the new flange size is by measuring the exposed outflow pipe’s diameter – these two components should share the same size.

The wax ring, meanwhile, should have the same diameters as the toilet’s elbow neck.

Step 5: Place the flange


Before installing closet flange, the first step is to set the new flange in place. It should be pressed into the drain’s aperture, and you may use the toilet T-bolts as a guide for positioning. The hub with a rubber sleeve should be facing up.

The distance from the wall should also be considered, with most flanges designed to be installed about 12 inches from the wall to the center of the flange, although adjustments may be needed based on the toilet’s size.

The flange can be rotated in different directions until a suitable position is reached. Before fastening the flange, make sure it’s flush against the floor and doesn’t create any visible gaps.

Step 6: Drill holes through the flange


After installing the toilet flange, the next step is to drill holes in the concrete for the screws. For this, we should use a smaller concrete drill bit than the screws. The number of bolts needed depends on the size screws for toilet flange, with most flanges requiring four fasteners.

To mark the concrete, use a marker right where the four holes in the flange are, and set the flange aside. Then, using a rotary hammer and a 1/2-inch concrete drill bit, drill a 1 1/2-inch hole into each of the marks formed on the concrete surface.

To avoid accidentally breaking the rear of the toilet sewer pipe, it is critical not to angle the drill towards it. Sewer pipe repair can be difficult and expensive if damaged.

Wearing safety glasses during the drilling process is also essential to prevent any debris or dust from entering the eyes.

Step 7: Secure toilet flange to the concrete floor


After drilling the holes, use masonry or concrete screws for toilet flange to keep it in place.

You can secure toilet flange to concrete floor using a screwdriver. It’s important not to overtighten the fasteners, as it could damage the flange and result in leakage from the toilet base.

For PVC toilet flange rings, be cautious not to screw in the anchors too deeply to avoid cracking the ring.

Step 8: Attach the wax ring


With the toilet’s base exposed, press the rounded edge of the wax ring over the elbow’s neck until it’s firmly sealed.

Another option is to place the ring on the toilet’s flange and slowly lower the toilet until its elbow neck connects with the wax ring. Twist the toilet gently without rocking it back and forth. This should help you securely attach a toilet to the floor.



Should the toilet flange be screwed to the concrete floor?

Yes, screwing the toilet flange to the concrete floor should help keep it in place. In case the flange still feels slightly wobbly, you can place a shim underneath it for more stability.

Note that the flange should be installed flush against the finished floor or no more than 1/8″ above it to prevent the toilet from rocking. The flange needs to be secured on cement floor, and a dry fit of the toilet should be done to check for rocking.

Can a toilet be installed directly on concrete?

Yes, a toilet can be installed directly on concrete if there is a drainage toilet pipe and accompanying plumbing in the spot you intend to install the toilet.

However, it is recommended to install a toilet flange to provide a secure base for the toilet and to prevent leaks.

If the floor has nothing to screw toilet flange to concrete floor, drill the required holes using a 1/4-inch masonry or concrete bit and a hammer drill.

What if my toilet has no flange?

If your toilet has no flange or your bathroom is in new construction, the fixture will need to be installed with one.

If a flange is missing, it is not possible to correctly secure a toilet. Bolting the toilet directly to the floor may lead to sewage leaks and rotting in basement concrete floor.

Installing a flange is typically done by a plumber or a knowledgeable DIY homeowner. These people can help you fix a broken toilet flange in concrete and prevent any damage to your plumbing system.


Understanding the process of installing a toilet flange on concrete floor is essential to ensuring a secure fit for your toilet and preventing leaks. Now that you’ve followed our guide on how to install a toilet flange on a concrete floor, you can take a deep breath and relax.

If you ever need to tackle another plumbing project, we’ll be here to guide you every step of the way. But for now, enjoy your newly installed toilet and feel proud of yourself for a job well done!

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