Installing a new toilet flange on a concrete floor can seem daunting, but with the right tools and techniques, it can be a straightforward DIY project. A toilet flange, also known as a closet flange, is a pipe fitting that connects the toilet to the drainpipe in the floor. It’s necessary to replace an old or damaged flange to ensure a water-tight seal between the toilet and the drain pipe.
When installing a new flange on concrete, you have to deal with the challenge of drilling into the robust material. But don’t worry, with proper planning and preparation, you can complete this project efficiently. Here is a step-by-step guide on how to install a new toilet flange on a concrete slab correctly.
What You’ll Need
Before starting the installation, ensure you have all the necessary supplies and tools:
- Replacement toilet flange for 3” or 4” drain pipe
- Wax ring
- Bolts for the toilet
- Hacksaw/pipe cutter
- Flat pry bar
- Screwdrivers
- Caulk/silicone sealant
- Shop vacuum
- Safety gear (gloves, eye protection, ear protection, dust mask)
- Hammer drill with masonry drill bit
- Concrete anchors
Step 1: Turn Off Water Supply and Remove Toilet
The first step is to turn off the water supply valve behind the toilet and flush to empty the tank completely. Sponge out any remaining water in the bowl.
Use a flat pry bar to remove the old bolts and nuts holding the toilet to the flange. Rock the toilet back and forth gently to break the wax seal. Carefully lift the toilet straight up and set it aside on cardboard or a tarp to protect the floor.
Step 2: Remove Old Flange
With the toilet removed, now you can see the old flange on the concrete floor. Use a flat pry bar to pop it free from the floor. You may need to chisel out any remaining concrete or caulk around the edges with a cold chisel.
Use a shop vacuum to clean up any debris or old wax around the toilet drain. Inspect the drainpipe coming up from the concrete to make sure it is intact and not damaged. Grind or sand any rough edges smooth.
Step 3: Measure and Cut New Flange
Examine the old flange and measure the inside diameter to determine if you have a 3” or 4” drain pipe. Purchase the same size replacement flange.
Place the new flange over the pipe to test the fit. If needed, use a hacksaw or pipe cutter to trim the bottom of the flange so it sits flush on the concrete floor. Remove any burrs or sharp edges.
Step 4: Drill Anchor Holes
Now comes the tough part – drilling holes into the concrete for the new flange anchors.
Mark the positions for the anchor holes based on the shape of the new flange. Commonly, closet flanges have 4 holes spaced evenly around the ring.
Use a hammer drill with a masonry bit the same width as your concrete anchors. Drill perpendicular holes about 1-3/4” deep into the concrete slab.
Thoroughly vacuum dust and debris when finished.
Step 5: Install New Flange
Place the new flange over the drain pipe, aligning the bolt holes with the newly drilled anchor holes.
Insert the concrete anchors and use a hammer to gently tap them flush with the surface of the flange.
Level the flange and use a screwdriver to tighten the anchors evenly so the flange is snug against the floor. Don’t over-tighten or you may crack the flange.
Apply a thin bead of caulk or silicone sealant around the base of the flange for added leak protection.
Step 6: Install New Toilet
You’re almost done! Now it’s time to install the toilet on the new flange.
First, install a new wax ring gasket around the flange, pressing it evenly into place. The wax ring creates a tight seal between the toilet and drainpipe.
Carefully set the toilet over the flange, aligning the bolt slots with the holes on the flange. Rock the toilet side to side slightly to press into the wax ring evenly.
Insert the toilet bolts into the slots and hand tighten the nuts to secure the toilet to the new flange. Don’t fully tighten yet.
Step 7: Caulk and Complete Installation
Apply a bead of silicone caulk around the base of the toilet to seal any gaps between the toilet and floor. Carefully wipe away any excess caulk with a damp rag.
Once the caulk has set up, use a wrench to tighten the toilet bolts the rest of the way. Don’t over tighten or you may crack the porcelain.
Turn the water supply valve back on and allow the tank to fill. Flush the toilet a few times and check for leaks. You may need to re-tighten the bolts after the initial test flushes.
Finally, install the toilet seat and enjoy your successfully installed toilet flange! Be sure to dispose of any old parts properly.
Tips for Installing a Toilet Flange on Concrete
- Use a carbide-tipped masonry drill bit for clean holes in concrete
- Vacuum dust often to keep the work area clean
- Wear safety glasses and gloves when handling rough pipe edges
- Apply caulk/sealant for an extra barrier against leaks
- Tighten flange bolts evenly to avoid cracking the flange
- Don’t over-tighten toilet bolts or you may crack the porcelain
Common Toilet Flange Problems
Installing the flange incorrectly can lead to leaks, clogs and other problems down the road. Here are some common issues to keep in mind:
Uneven Flange
If the flange is rocking or uneven, it won’t make a tight seal with the toilet. This can cause leaks and rocking of the toilet. Use shims or extra caulk to level the flange.
Cracked or Damaged Flange
Cracks or damage in the flange will lead to leaks. The flange must be replaced. Be careful not to overtighten bolts to avoid cracking a new one.
Improper Flange Height
The flange should be about 1/4” above the floor. If it is too high, the toilet will rock and leak. If too low, blockage can occur. Adjust height by adding a flange extender or replacing the flange.
Rust and Corrosion
Moisture causes flanges to rust over time. Replace severely corroded flanges. For minor rust, sand and paint the flange to inhibit further corrosion.
Offset Flange
If the flange is offset from the drain pipe, it can obstruct flow and cause leaks. The pipe must be repaired and a centered flange installed.
FAQs About Installing a Toilet Flange on Concrete
How do you attach a toilet flange to concrete?
Use a hammer drill and concrete anchors to secure the flange to the concrete slab. Drill matching holes in the concrete for the anchor bolts, insert anchors, and tighten evenly.
What kind of drill bit is best for concrete?
Use a hammer drill with a masonry drill bit carbide tip. This allows you to drill holes in the robust concrete material.
Can you install a toilet on a concrete floor?
Yes, a toilet can be installed on concrete by using a closet flange attached with concrete anchors drilled into the floor. The wax ring seals the toilet to the flange.
Do you need a toilet flange on concrete?
Yes, a flange is required on concrete floors to provide a stable, secure way to install the toilet. The flange attaches to the drain pipe and anchors to the concrete.
What is the proper height for a toilet flange?
Ideally, the toilet flange should be 1/4” above the floor. This ensures the wax ring can make full contact and an airtight seal. Adjust flange extenders can help get the right height.
Can I install a toilet without removing the old flange?
It’s best to fully remove the old flange and install a new one for proper positioning and sealing. Covering an old flange with a new wax ring often leads to leaks.
What happens if the toilet flange is not sealing?
If the flange isn’t properly sealed, water can leak out around the base of the toilet. This can damage the floor over time. Reseat or replace the flange to stop leaks.
How do I stop my toilet from rocking with a new flange?
If the toilet rocks after flange replacement, the floor may be uneven. Use shims under the toilet or extra caulk around the base to stabilize it. Tighten bolts carefully.
Can I replace just part of the toilet flange?
It’s best to replace the entire flange assembly if damaged or corroded. Partial flange repairs often leak. Get the correct 4” or 3” flange for your drain size.
How long does a toilet flange last?
Most toilet flanges are made of plastic and last 5-10 years with proper installation. Regular maintenance helps maximize the lifespan. Eventually seals fail and leakage occurs, signaling the need for replacement.
Conclusion
Installing a new toilet flange on a concrete floor is a challenging but doable DIY project. With the proper closet flange for your drain size, wax seal, caulk, and concrete anchors, you can securely fasten the new flange and toilet. Precision drilling into the concrete and careful leveling of the flange are the keys to success.
Following the safety tips outlined will lead to an easier installation. Take time to do preparation work like turning off water and removing toilets properly. With this comprehensive guide, you can replace a failing or damaged toilet flange on a concrete slab and restore full functionality to your toilet.
