The Ultimate Guide to Installing a Toilet Flange on Concrete: A DIYer’s Dream (and Plumber’s Nightmare)

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So, you’ve got a wobbly throne, huh? Maybe it rocks a bit when you sit or, worse, it’s leaking all over your nice bathroom floor. Well, friend, nine times out of ten, the culprit is a bad toilet flange. Don’t worry, though – swapping out that old flange for a shiny new one is totally doable, even if your bathroom floor is solid concrete. And hey, doing it yourself means more cash in your pocket!

Ready to roll up your sleeves and get your hands a little dirty? Let’s dive in!

What the Heck is a Toilet Flange Anyway?

The toilet flange is that unassuming, round piece tucked away beneath your toilet. You probably don’t give it much thought, but trust me, it’s got a crucial job: it’s the anchor that keeps your toilet securely fastened to the floor and prevents it from wobbling. But that’s not all it does. This handy little gadget also acts as the connector between your toilet and the drain pipe hidden beneath the floor.

See, the flange ensures that everything that goes down the drain actually goes down the drain. Without it, all that water in your toilet would spread out over your bathroom floor everytime you flushed. And if left to continue, it will eventually leak out underneath your floor, and damage your subfloor.

So, yeah, the flange is important.

But fear not, DIY warrior! Replacing that flange is a totally manageable task, even if your bathroom floor is made of rock-hard concrete. We’ll walk you through the entire process, so you can bid farewell to wobbly toilets and leaking nightmares.

Why Concrete is a Different Beast

Alright, let’s be real for a sec. If your bathroom floor was made of good old-fashioned wood, installing a toilet flange would be a walk in the park. But concrete? That’s a whole other animal, and securing a toilet flange to concrete requires some specialized tools and a slightly different approach than you would take with wood. But don’t let that scare you off! We’ll guide you through every step of the process, from picking the right flange to drilling those holes in the concrete. 

Before You Get Started: Gather Your Gear

Gathering the right tools will help you get the job done efficiently, safely, and correctly. So, let’s take inventory and make sure you’ve got everything you need to tackle this project like a pro.

  • New Toilet Flange: Choose one that matches your drainpipe size (usually 3 or 4 inches). Consider newer options like the Set-Rite flange for uneven floors or PVC flanges for extra durability.
  • New Wax Wing: Since it’s the seal that protects the flange and the toilet, you’ll want a new one of these, too.
  • Hack Saw or Reciprocating Saw: This is for cutting the old flange (if there is one).
  • Hammer Drill and Masonry Bit: Concrete doesn’t play nice with regular drills. You’ll need a hammer drill and a masonry bit to make those holes for the flange bolts.
  • Screwdriver: For tightening the flange bolts.
  • Wrench: For tightening the flange to the drainpipe.
  • Putty Knife: For scraping away old wax and debris.
  • Tape Measure: For precise measurements and placement.
  • Level: To make sure your flange is perfectly level.
  • Buckets and towels: You’ll have some water in the tank that needs to be drained, and you will make a small mess.
  • Safety Glasses and Gloves: Protect those peepers and hands!

Step-by-Step Guide: Let’s Get Down to Business

Alright, gear’s gathered, now it’s time to dive into the nitty-gritty of this project. Don’t worry, we’ll take it slow and steady, one step at a time. By the end of this, you’ll have a toilet flange that’s so secure, it could withstand a hurricane (not that we recommend testing that theory).

Turn Off the Water and Remove the Toilet

Before you go swinging any tools around, let’s make sure we don’t end up with a mini-Niagara Falls situation. Turn off the water supply valve behind the toilet, then give it a good flush to empty the tank and bowl. Disconnect the water supply line. This is where the bucket and towels come in handy, because any extra water in the tank will drain out the hole when you disconnect that line. So take your time, let it drain, and use the towels to mop up and last remaining water. 

Next, unbolt the toilet from the floor. Once the toilet is free, carefully lift it off and set it aside – preferably somewhere it won’t get in your way. This might take a bit of muscle, so don’t be afraid to call in a friend for help. 

Say Goodbye to the Old Flange

If you’re dealing with an old, worn-out flange, it’s time to bid it farewell. Grab your saw and carefully cut it off as close to the floor as possible. Don’t worry if it’s not perfectly flush – we’ll take care of any rough edges later. Clean up any debris and use your trusty putty knife to scrape away any old wax or sealant that’s clinging to the drainpipe.

Prep the Drain Pipe

This step is like getting ready for a first date – you want it to be perfect. Measure the height of the pipe sticking out of the floor to make sure it’s the right size for your new flange. If it’s too high, you might need to cut it down a bit.

Position the New Flange

Now for the fun part! Take your shiny new flange and place it over the drainpipe, making sure it’s centered and perfectly level. We don’t want any wobbly toilets, right? Use a pencil to mark the holes where you’ll be drilling for the flange bolts.

Drill, Baby, Drill

It’s time to unleash your inner demolition expert (in a controlled way, of course). Grab your hammer drill and masonry bit, and drill holes into the concrete at those pencil marks you made. Go slow and steady – you don’t want to crack the concrete. Make sure the holes are deep enough to fit the flange bolts snugly.

Secure the Flange

Pop those flange bolts into the holes you just drilled and tighten them up with your screwdriver. Then, give the flange itself a good twist with your wrench to secure it to the drainpipe. Double-check that everything is nice and level – you don’t want your toilet rocking like a ship on the high seas later.

Reinstall the Toilet

Grab that new wax ring you bought and place it on the bottom of the toilet. Now, carefully lower the toilet back onto the flange, aligning the holes with the bolts. Tighten the bolts until the toilet is snug and secure. Don’t go overboard, though – you don’t want to crack the porcelain. Reconnect the water supply line, turn the water back on, and give yourself a pat on the back!

Test for Leaks

This is the moment of truth! Flush the toilet and keep an eagle eye out for any leaks around the base. If you see any water escaping, try tightening the bolts a bit more. If the leak persists, you might need to adjust the wax ring or call in a plumber for a second opinion.

Troubleshooting: Common Issues and How to Fix Them

Okay, so you followed the steps perfectly, but there’s some water leaking out. Don’t panic! These hiccups are totally normal, and we’ve got your back. Here are some common issues you might encounter and how to troubleshoot them like a seasoned DIY pro:

  • Uneven Floor: If your bathroom floor is uneven, you might need to use shims or a self-leveling compound to create a level surface for the flange. The Set-Rite flange system is also a great option for uneven floors.
  • Misaligned Flange: If the flange isn’t aligned with the toilet drain, you might need to use an offset flange to correct the position.
  • Leaks: Leaks can occur if the wax ring isn’t sealed properly or if the flange isn’t tightened enough. Double-check your work and make any necessary adjustments.

When to Call a Plumber

While installing a toilet flange on concrete is doable for most DIYers, there are some situations where it’s best to call in a professional:

  • Cast Iron Drain Pipe: If your drain pipe is made of cast iron, it’s usually best to let a plumber handle the installation. Cast iron can be tricky to work with and requires special tools.
  • Extensive Damage: If there’s significant damage to the drain pipe or surrounding concrete, a plumber can assess the situation and recommend the best course of action.

The Bottom Line: A Toilet Flange that’s Rock Solid

Installing a toilet flange on concrete might seem like a daunting task, but with the right tools and instructions, it’s a project you can definitely tackle. Not only will you save money, but you’ll also gain the satisfaction of knowing you did it yourself. So go ahead, conquer that concrete, and give your toilet the solid foundation it deserves!

Meet Marco, a lifelong tinkerer and DIY enthusiast, developed a passion for plumbing after fixing a leaky faucet in his own home. Years later, he turned that passion into a thriving business, Amarco Plumbing, where he shares his knowledge and expertise with the community.