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Tutorial 1: Toilet flange installation on concrete

Sioux Chief Closet Flange  Installation or repair of a closet flange or its attached plumbing system can be tricky and when adding concrete to the equation it just complicates things even more. This tutorial will walk you through installation of a closet flange on a concrete surface. Future tutorials will show rough in installation on a wood surface, repair of a damaged flange, installation of a toilet, and many more residential plumbing tutorials.



Tutorial Description

toilet flangeThis tutorial is for someone who has the plumbing waste system installed for a toilet in concrete and a 4" stand pipe available for the flange to install in.

(This tutorial will also work for a 3" pipe but the hub of the flange must fit around the pipe. In this tutorial we use 4" pipe and the flange will fit into the pipe. )

Often in older homes that are set up for a future rough-in, the closet flange will be either installed on the pipe at rough in, or a 3"- 4" pipe will be left buried below the concrete for future use. Often this area is filled with foam or a box of dirt. The existing buried pipe can then be easily exposed for future hook up.

In many cases the closet flange will be installed during rough-in. This can cause issues when flooring is installed. The bottom of the flange will need to be flush with the top of the finished floor with no gap allowed.

If a 3" pipe was left buried for future use,  the closet flange hub will need to be fit over the closet riser which usually means removal of some concrete around the diameter of the ABS or PVC pipe. If the toilet riser is a 4" pipe then a closet flange can be purchased at your local plumbing wholesaler, home improvement store, or any hardware store which then will slide into the 4" ABS or PVC riser.

Pipe measurements:
3"  ABS/PVC =    3.5 Inches 
4"  ABS/PVC =    4.5 Inches

Measurements are for the Outside Diameter or OD of the pipe.

Toilet Flange Installation

Preparing to install the flange

To start off with you will need to get all of the tools and parts for the project together including concrete fasteners , glue and a rag for clean up. Below you can get more information on the needed plumbing supplies.



Hammer Set Anchor

  This style fastener is great for securing the closet flange ring to the concrete surface. They come in various lengths and thicknesses to accommodate any type of project where fastening to concrete is required and are easy to use. They can be picked up at your local plumbing wholesaler, home center or hardware store. A great thing about this fastener is it's made of lead so it will not corrode and it's a very strong fastener that will hold up under extreme conditions. For this job you will need 6-8 anchors with a length of 2-1/2" - 4" . They will need to go though the toilet flange and several inches into the concrete to provide a secure installation.


abs glue

Plastic Pipe Glue

  You will need ABS or PVC cement depending on the type of plastic pipe you are using. On the West coast of the United States you will mostly find ABS used and on the East coast PVC is preferred. Both types of pipe are fine to use but ABS has many advantages over PVC and in future articles we will discuss ABS and PVC in more detail. At this time you should have a fresh one quart can of either ABS or PVC solvent cement. We will be working with large diameter pipe so a larger dauber which comes in the quart cans of solvent cement is required.



Clean Up Rags

  When working with solvents, glues or paints it is a good idea to have some cloth or paper towels available for emergency clean up. If you spill a can of glue, having some clean up rags handy can be a project saver.



In case of spills with solvents, glues or paint's you can use wood chips or saw dust to soak up the excess spilled liquids.


The Tools

  • Pencil
  • Tape Measure
  • Hand Saw
  • Rotory Hammer drill
  • Claw Hammer
  • Flat Headed Screwdriver


So now you have a good idea of the tools and supplies you will need for the project so lets get started. First make sure your work area is cleaned up and clear of obstacles. A cluttered work area can have disastrous results while completing a plumbing project of this scale. One wrong cut or slip of the drill and the project can become a nightmare.




Closet Flange Installation

Start by measuring from the wall behind the toilet area to the center of the pipe coming up through the concrete.

Closet Flange Installation


When you look at and purchase a toilet something to remember is that toilets have different rough-in dimensions. This rough in dimension is determined by measuring from the front of the rough stud in the wall to the center of the water closet riser. If the wall has a material such as Sheetrock or tile this will need to be accounted for by adding the material's thickness.

Tip  toilet_cutIf a toilet is installed prior to removal and you need to know what the measurement is. Just measure from the finished wall to the portion of the toilet where the interior p-trap goes towards the floor.
Toilets can be purchased from 12" -14" rough. Anytime you are purchasing a new toilet its a good idea to measure before the purchase or ordering of the plumbing part is final.

Closet Flange Installation

Above I have my marks and they extend out beyond the outer diameter of the closet flange so I can see the lines after the flange is install on the pipe.

Closet Flange Installation

Begin by laying your saw blade as flat against the concrete as possible. Saw as tight and close to the concrete as you can. It can be touched up with other tools so at this stage it need not be perfect.  Do make sure your cut is level. You can also purchase or rent an inside pipe cuter which makes this job a snap. Check at your local plumbing wholesale house, hardware store or tool rental company.

Closet Flange Installation

Once you have made your cut you can use a sharp knife or power tool such as a rotary tool to ensure that the plumbing riser is flush or slightly below floor level.
The concrete will also need to be removed if it is not level. Usually this can be done with a hammer and some light tapping at the concrete edge. Do not remove to much because the anchors need something to hold on to. If your pipe is a 3"  pipe then you will need to remove some concrete.

In most cases you will need to remove some foam material around the pipe and this will allow for the flange to fit down over the pipe.

Also remember to clean up the inside edge of the pipe for any burs or rough edges created during cutting.

Closet Flange Installation

Now it is time to glue the plumbing fitting onto the pipe. First lets get ready by making sure our drill has power, our glue can lid is loose, our flat screw driver is ready and we have the right amount of anchors ready. The toilet flange has a slot on each side for the closet bolts to fit in. Make sure these are on the left and right side centered when you slide the fitting onto the pipe. Once glued the fitting will not rotate or move unless designed to.

Start by applying plenty of glue to the inside of the fitting at the hub. Now coat the out side of the riser pipe and slide the fitting onto the exposed pipe while turning the flange to the proper position with the slots to the left and right at 90 degrees. Mark where the holes on the flange are once you are sure the flange is plumb and level. Drill two of the required fastener holes across from each other. Inert an anchor in the first hole and gently tap it into the hole with the flat screw driver and hammer. If the anchor does not go in smoothly or bottoms out before going in all the way. Pull the anchor out and drill to the proper depth and test again. Once the two anchor lead sleeves are install and you know the flange is where you want it secure the anchors by hammering in the nail which will split the lead and wedge it into the concrete holes.

See image below.

Closet Flange Installation

Now finish drilling the rest of the holes

Closet Flange Installation

Start inserting the next two anchors.

Closet Flange Installation

The screw driver just pushes the lead sinker in making sure its level and all the way in.

Closet Flange Installation

Test the rest of the anchors and drill out deeper if needed.

Closet Flange Installation

Now that all the anchors lead sleeves are in place you can finish hammering all the nails in.

Closet Flange Installation

Below all the anchors have been installed.

Closet Flange Installation

Make sure you note the position of the slots for the toilet bolts as it is a critical factor when installing a water closet flange.


A finished product that is secure, safe and will last a life time. I hope this tutorial was helpful and if you need any project advise just contact us at This email address is being protected from spambots. You need JavaScript enabled to view it.


If you do not feel comfortable working on mechanical projects then  you should contact a local plumber for repair or installation of plumbing.


Plumbing Plumbing Tips

Maintain Sink Drains As a precaution every six months to a year. Go around to all the sinks in the home and tighten all the slip joint nuts on the drains.