How to Install a Toilet

A white toilet on a vinyl floor
  • 1-3 hours
  • Intermediate
  • 150-250
What You'll Need
Putty knife
3 or 4-inch drain pipes
Closet bend
Floor flange
Wax gasket
Silicone caulk

When you’re putting in a new bathroom or remodeling an existing one, installing the toilet is one of the most important things to get right. Here are some general instructions and precautions for roughing in, as well as installation procedures for tying into your present drain waste vent and supply systems.

Most Common Mistakes

Violating or ignoring local code restrictions

Using pipes that are too small

Attaching copper to galvanized without a brass or dielectric fitting between the two

Not using PTFE tape or pipe compound at threaded joints

Not leveling your fixtures

Cutting supply stub outs too short to install the shutoff valves

Not properly aligning tubing into fittings or stop valves

Hint: When turning the water back on in your home, always run the outside hose valve or flush your toilets to bleed dirt and air from the lines. This debris can cause problems in your sink faucets and other plumbing trim.

Installing Your Toilet

Pipes required include a cold water supply stub out with a shutoff valve and flexible tubing for above the valve. This is possibly the single, most troublesome fixture to install as it requires its own two-inch minimum vent and a drain of at least three-inches in diameter. If the toilet is situated on a branch drain, it cannot be upstream from the sink or shower. The minimum side distance allowed from the center of the toilet bowl to a wall is 15-inches, and 12-inches from the center of the bowl to a bathtub. Clearance from the front of a bowl to a wall or fixture should be 21-inches.

Step 1 - Rough In the Closet Bend and Toilet Flange

man with toilets and tools in a bathroom

The closet bend and toilet floor flange must be roughed in first. If you’re replacing a toilet, you need to scrape up the old wax gasket. A putty knife works well for this. Remove the old bolts from the floor flange and scrape the flange clean to prevent leaks at the base of the new bowl. If the old flange is cracked or broken, replace it with a new floor flange.

Doityourself’s plumbing consultant Mark Vander Sande adds, “Replacing a flange is not an easy thing to do. It requires cutting the existing drain pipe below the flange and replacing the flange and the pipe. If it’s PVC it’s not so difficult. It requires a coupling the size of the pipe, either three or four inch, a short piece of pipe, and a new flange. If its cast iron, you need a fernco fitting, cutting the cast iron with a sawzall and replacing the pipe with PVC. There is a repair flange, called a spanner flange. This goes underneath the existing flange with the toilet bolt through it. It’s easier and less expensive and it works fine.

Step 2 - Secure the Floor Flange

Position the floor flange so the underside of the flange is at the level of the finished floor. It is always best to install the finished floor so that it runs underneath the toilet. You may need to use a piece of finished flooring material if the floor has not yet been installed. Now you can finish tightening the screws that hold the floor flange to the floor. Put a small level on the flange while tightening to be sure it is level.

Step 3 - Set the Floor Bolts and Install the Wax Gasket

Set the new floor bolts in plumber's putty and insert them through the flange, adjusting the bolts so they line up with the center of the drainpipe. Position the new wax gasket on the flange, with the bolts “molded” into the wax to hold them in place.

Step 4 - Set the Toilet on the Flange

Caulking around the bottom of a toilet

Using the bolts as guides, lower the bowl into place over the flange. Press down firmly. It is important you feel the toilet being pushed into the wax ring. If you don’t feel this, the flange is set too low and you will not get a good wax seal between the flange and the horn (waste outlet). Also, if the wax ring is cold, it will not properly seat. You may need to warm it in the sun for awhile until it is pliable.

Step 5 - Level and Secure the Bowl

Use a level to level the bowl, adding shims where necessary. Also, be sure the toilet is square and aligned with the wall. Then tighten the nuts and washers onto the bolts by hand.

Mark says, “It’s important to follow these steps. The toilet will come with bolt caps and washers for the bolt caps. The washers need to go first on the bolts coming out of the floor for the toilet, then the metal washer that came with the bolts and then the nut. You may have to cut the bolt so the cap will fit on. Make sure the bolt is secure before cutting, otherwise it will move around. This is not a big deal, just tighten it. But don’t over tighten, it could break the bowl.”

Step 6 - Set the Tank in Place

Place the rubber tank cushion, if one is needed, into position on the rear of the bowl and fit the rubber gasket onto the flush valve opening on the bottom of the tank. Position the tank over the bowl, then tighten the nuts and washers onto the mounting bolts. It’s important to hand tight both bolts until secure and tighten one side at a time, slowly going from one to the other until tight. If one side is tighter than the other when the other side is tightened it can and will break the tank.

Step 7 - Secure and Seal the Tank

Tighten the hold-down bolts at the base of the bowl with an adjustable wrench. Use your level to assure the bowl is still level. Place the decorative caps over the bolt ends. Seal the base of the toilet bowl with silicone caulk. Hook up your water feed to the tank and turn the water on. Now your toilet is installed.