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What Size Screws for Toilet Flange in Concrete

Replacing your toilet flange on your concrete flooring may seem daunting. You need the right equipment and a can-do attitude. But, what is the right equipment?

Start with some power tools, a putty knife, and a few sturdy screws. I know what you’re thinking. What size screws do I need? Finding what size screws for toilet flange in concrete is easier than you might think (if there’s nothing to screw your flange into, read here).

What Size Screws for Toilet Flange in Concrete

It is best to dig up the last screws that the flange used. This approach can give you a good sense of what the new screws look like. If the initial screws were faulty, most concrete slabs will be fine with ¼” x 1 ½” screws.

How To Know if Your Toilet Flange Needs New Screws

Before finding the right size screws for a new toilet flange, first figure out if it needs new screws. There are two telltale signs of a defective set of flange bolts. One is very obvious, while the other requires paying little attention.

The obvious one is leaking coming from the base of the toilet. Those kinds of leaks suggest you have a loose toilet. That means one of two things. Either the flange is loose or there’s a crack in the bottom of the porcelain.

If you inspect for cracks but don’t find any, you have an answer. It must mean the first explanation is true, and a replacement flange is in that toilet’s future. 

The second sign may not be evident right away. It requires a few more accidents before someone notices the problem. If you notice the commode is a bit loose or wobbly as you try to do bathroom business, you might need to do a repair.

At first, it may seem like you sat down too fast and messed up the toilet bowl balancing act. But, after a few repeated incidents, it’ll become more clear that it is the toilet seat that shakes from side to side every time you try to go number two.

At that point, you’ll know that a loose connection underneath the toilet needs some fixing. That means it is time to break out the tools and replace that toilet flange.

A Quick and Easy Way To Find the Right Size Screws

The simplest way to figure out what screws you need for your toilet flange is to look at the existing ones. 

Note that broken, corroded, or wrong-sized screws can still be helpful. They can be a guide on what you should look for when visiting the hardware store.

Retrieving them, and eventually replacing them, is not very hard. With a little elbow grease, the right tools, and possibly a back brace, you can do it. These steps will allow you to unscrew the nuts in your flange every time.

  1. First, remember to turn off the water so you don’t get splashed when you flip the bowl. Find the turn-off valve and turn it clockwise (to the right) as far as possible.
  2. To ensure the water is off, grab your trusty wrench. Disconnect the water supply line from the shut-off valve.
  3. After that, it is a simple matter of unscrewing the screws with a screwdriver. Inspect the screws using a flashlight or natural light to see the damage and what kind of screws they are. 

Of course, having a ruler nearby is good for getting a general size description.

Find the Right Size Screws

Other Methods of Finding the Right Size Screws

What if the screws under the toilet are unrecognizable? In that case, you need to get a little more creative. Tap into a little brainpower and some hardware know-how to figure out what kind of screws you need.

Short on hardware know-how? That’s okay! This article will give you all the know-how required to figure it out without a professional. Since you know that you’re working with concrete, you can skip the wood screws, sheet metal screws, or other screws.

Note that the only difference between the screws and concrete screws is the length, as longer screws work better for thick concrete. Those screws are usually ¼” by 1 ½” long.

Hardware stores make your life easier on this front. They label screws to help you find what you need for a specific project. As a quick note, another name for a large screw used for toilet flanges is an anchor.

For an even easier trip to the hardware store, find the nearest clerk and ask for help. Somebody at the hardware store should be able to help you find the anchors you need for your toilet flange. 

Extra Items You’ll Need Other Than Anchor Screws

Congratulations! You found the right size screws to secure your toilet flange in the concrete floor. You’re ready to start your project. First, you need some other tools and materials before starting the project. This list includes:

  • Washers
  • A Heavy-Duty Drill
  • Lubricant (oil or soap)
  • Extra Screws
  • Screw Drill 

The washers will ensure that the screws stay in place after you screw them in. They create another barrier of friction or the nut so it can secure the long haul.

Washers are relatively cheap and helpful for jobs other than tightening a flange. It’s always nice to have a set of those lying around.

The heavy-duty drill helps you make pre-holes in the concrete before inserting the screws. Assuming this is a brand new concrete slab, pre-drilling a cavity is necessary. It ensures the fasteners don’t break during insertion.

Screwing Toilet Screws

If you are replacing old screws, the holes should already be there, making a heavy drill unneeded.

Lubricant is necessary to reduce friction so screws twist in without unnecessary damage. Drilling can make screws hot, which impairs the structural integrity of the screw. Without lubricant, your new screws won’t last as long. 

Nobody is perfect, so don’t worry if you break a screw or two trying to install your new flange. It’s a good idea to have extra screws on hand before you get started, just in case.

Using a screwdriver is a good option, but a better option would be to use a screw drill to drive the bolts in much quicker. Always remember to work smarter, not harder.

How to Safely Screw Into Concrete

Here comes the fun part, where it is time to install your flange into the concrete slab safely. After all, you do not want to break the new screws you spent all day searching for.

After you flip the toilet and remove the previous screws, things get a little trickier. Break the task into simpler steps and be careful! 

  1. Drill a hole into the concrete slab, making sure to go a little deeper than the length of the screw. This extra space gives the screw enough room for a secure fit without excess wear.
  2. Align the new flange with the drain pipe.
  3. Place each screw into the hole, making sure not to cover any of your pre-drilled areas. 
  4. Drill the screws into the concrete slowly and then speed up once they have gone in about a quarter inch.
  5.  Repeat this for the remaining screws and then replace the toilet when ready.

Final Thoughts

Phew! That was a challenge, but probably not as bad as you thought. Finding the size of the screws you need for the toilet flange in concrete is easy, right? 

It’s easiest to match up your new screws with the old ones. That’s not always an option, so you should be okay with ¼” x 1 ½” screws rated for thick wood.

At any rate, once you find the screws you’re looking for, replacing the toilet flange should be a cakewalk. Just make sure you have the tools necessary and the will to get it done!

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