Five Best Practices when Installing a Toilet Flange

Whether you're a new pro entering the industry or a seasoned plumber in need of a quick refresher, here are five best practices when installing toilet flanges. We are also offering a review of toilet-flange types and options.  

1.    Pay attention to flange height

Proper flange height is key to preventing leak paths. A best practice is to install the toilet flange on top of the finished floor. If you install the toilet flange flush with the finished floor, or even below the finished floor, leak paths will form, because the flange won't be at the correct height to accept the horn at the bottom of the toilet.

If you're unable to install the flange on top of the finished floor, you can use spacers that mount on top of the existing flange. There are also kits that allow you to install spacers under the toilet flange during installation to ensure the bottom of the flange is flush with the finished floor. 

When you install PVC spacers on top of a PVC toilet flange, you will solvent weld it together. Or you can use a 100%-silicone sealant to make sure you have a watertight seal between the two layers.

2.    Always use rust-proof screws to anchor the flange to the subfloor

Another important step to keep in mind is to use rust-proof screws when installing or repairing a toilet flange. We don't recommend drywall screws, because they will deteriorate over time if they come in contact with water. At that point, movement can occur, the toilet flange can become damaged, and the pipe connection can become compromised. 

3.    Keep bolt slots clean and clear of debris

If you're installing the toilet flange before setting the tile or the flooring, be sure to use painter’s tape to cover the slots where the toilet bolts will go. Some plumbers might even tape cardboard over the flange while setting the floor. That's because mortar can easily enter these slots, causing you to have to spend unnecessary time trying to keep it clear of debris or clean it out before you're ready to set the toilet.

4.    Use a flange with a knockout or a mechanical test plug

Using a closet flange with a knockout plug will depend on the application. For new construction or remodels, there are flanges with knockout plugs that allow you to test the system without having to use a test ball or plug, while also keeping sewer gasses from escaping. The knockout plug will easily and cleanly break out, eliminating the possibility of falling down the sanitary sewer line after testing.

If you’re remodeling a bathroom and keeping the existing flange, a mechanical test plug will be the best option to keep sewer gasses from escaping while work is completed. A mechanical test plug fits inside the flange and has a gasket that is expanded with a wing nut, providing an airtight/watertight seal.

These plugs/knockouts will also prevent debris from entering the waste system during new construction and remodeling projects.

Note: If just the flange is broken, you can use a convenient flange repair ring, like Oatey's Fix-It Flange Repair Ring, to securely reinstall the toilet. A product like this makes repairs easy, because installation doesn't require solvent cementing or any special tools. Instead, the ring can be installed above the broken toilet flange with four screws and silicone sealant.

Repairing a toilet flange, versus completely replacing it, results in faster installation, because you need not remove the existing flange and plumbing connection. For professionals, the result is a speedier service call, saving time and money.

This blog details step-by-step instructions: from assessing the problem, to prepping the toilet, to fixing the existing toilet flange. However, if you determine the flange is cracked beyond repair after an inspection, the next step would be to remove and replace the existing flange.

After removing an unrepairable toilet flange, it's important to select the correct flange type for replacement, based on the pipe material. But before you head to your local supply house or the nearest hardware store to purchase a new toilet flange, let's explore the different types to ensure you choose the correct toilet flange for your particular application.

5.    Use the right toilet flange type

Today's market offers a variety of toilet flange types, based on material composition. Among the options are PVC, ABS, cast iron, brass or materials based on specific application needs.

Oatey Toilet Flanges come in the widest variety of sizes, materials and configurations, with options in PVC, cast iron, ABS. No matter what your toilet flange needs, Oatey has the part you need to do the job right. Toilet-flange types include open and closed in 3-inch to 4-inch sizes.

The choice of toilet flange depends on the material of the DWV pipe it is connected to. If you have a PVC pipe connection, you should install a PVC closet flange. A cast-iron connection will require a cast iron toilet flange.

Some older homes may still have a lead bend in place, relying on a brass closet flange and requiring a more traditional connection method. You may be familiar with this connection method: It involves peening the lead to the inside of the closet flange and joining the two materials together with solder. 

Most of the time, when repairing a brass flange, the lead material may have deteriorated beyond repair. If this is the case, the old lead bend must be replaced.

Specialty Options

●   45-Degree Closet Flanges are designed for applications in which clearance doesn't allow for normal flange installation, such as the Oatey® ABS or PVC 45-Degree Closet Flange with a Stainless Steel Ring. With the former, the hub comes off the bottom of the closet flange at a 45-degree angle. This is helpful if there is an obstruction beneath, or if you need clearance where an application doesn't allow direct attachment vertically into the closet flange.

●  Offset Closet Flanges: Used for PVC or ABS applications, the Oatey® Level Fit Offset Closet Flange can be rotated for precise alignment of bolts and screws. The rings provide flexibility with a 360-degree swivel.


As a result, if floor joists prevent the closest flange from being centered during installation, the Level Fit Offset Closet Flange offsets the hub of the closet flange around that joist obstacle. That way, you can still install the toilet where it needs to go. This flange is available with a stainless steel or metal ring.

Now that we have explored best practices when installing toilet flanges, you are ready to ensure a good seal and leak-free installation.

Related Resources


Oatey Liquilock - Water Solidifier

How to Install a Wax Ring