How to Install a Toilet From Scratch

Last Updated on January 19, 2022 by toilethaven

Installing a toilet from scratch may seem like a daunting task but it is actually very easy. A plumber will charge you between 125 to 300 dollars to install a toilet depending on the location and job difficulty. DIYing iy will save you as much.

There is a difference between installing a toilet from scratch and replacing one. While replacing a toilet, you already have an old toilet that you want to remove and install a new one.

To install a toilet from scratch means you are installing a toilet where none has existed before, typically in a new bathroom. If you want to know how to replace a toilet, check this detailed post out.

Installing a toilet from scratch involves the following steps:

  • Install the shut off valve
  • Install a toilet flange
  • Install the wax ring
  • Install the toilet bowl
  • Install the toilet tank
  • Test the new toilet
  • Install the toilet Seat

Materials and Tools Needed

  • New toilet
  • Shut off valve
  • Water supply line
  • Toilet Flange
  • Wax ring
  • Pipe cutter
  • Internal pipe cutter
  • Drilling machine
  • Adjustable wrench
  • Screwdriver
  • Pipe glue
  • Measuring tape
  • Mini hacksaw

Buying the Materials

People always struggle to buy a good toilet. A toilet being a long term investment, you will surely want to have the best one possible. The best toilet if carefully selected can serve you for a long time.

There are several things that you need to check out before buying a toilet. First you will need to determine your toilet rough-in. The rough-in is the distance between the rear finished wall and the center of the toilet drainpipe.

While measuring a rough-in, make sure that you measure from the finished wall and not the baseboard. The standard toilet rough-in is 12 inches although some toilets have a 10 or 14-inch rough-in.

The next thing you will need to know is your toilet dimensions. This include the height, width and depth/length. If you have a small bathroom, you should consider buying a small/compact toilet.

To find more on all the things you should consider before buying a toilet check out this post.

Go ahead to also buy the shut off valve, the supply line, the toilet flange and the wax ring. You may also opt to use a rubber seal gasket instead of a wax ring since it is less messy/gross.

How to Install a Toilet

Below is a step by step guide on how to install a toilet from scratch. You will either have a one-piece or a two-piece toilet. Installing a two-piece toilet takes longer since you have to install the bowl then the tank. It is however advantageous because you can install it all on your own.

With a one-piece toilet, the bowl and the tank are joint together and you will therefore have to install it in one go. It takes less time to install but some one-piece toilets are so heavy that you will need an extra pair of hands to help you install it. Some people still install them all alone but there is always a danger of dropping and breaking it.

 Step 1: How to Install a Toilet Shut Off Valve


A toilet shut off valve is a small knob installed on the wall behind the toilet. It provides you with a way to turn off the water flow to the toilet when doing toilet repairs without having to turn off the main house water supply.

This is how you install the toilet shut off valve:

  • The water supply pipe will be protruding a couple of inches into the bathroom but will be plugged off. You will therefore need to cut the pipe about 2 inches from the wall.
  • Before that, shut off the water to the main house. If there is a bathtub or sink in the bathroom turn on its water to drain the water already in the pipes.
  • Place a small bucket under the toilet water pipe and give it a clean cut. Some water will start dripping into the bucket so wait until the pipe is completely drained.
  • The toilet shut off valve is designed in such a way that you will not need to thread the pipe. It has a steel nut and brass ring which is installed between the valve and the nut. The nut is reverse-threaded such that when you tight it the brass ring will be deformed and therefore making a watertight seal.
  • Put in the chrome plate in the pipe and push it to the end. Its work is basically aesthetics.
  • Put the nut in the pipe in such a way that its threads are facing outwards.
  • Push the brass ring inside the nut.
  • Bring on the shut off valve and start reverse-tightening the nut until its snug.
  • Use to wrenches to completely tighten the valve in place.

Step 2: How to Install a Toilet Flange

A toilet flange is a circular pipe fitting that connects the bottom of the toilet to the toilet drainpipe. It is also called a closet flange since toilets were in the past known as water closets.

Toilet flanges are universal. They have a diameter of 3 or 4 inches which fits into the drainpipe. Be sure to measure the size of your drainpipe prior to buying a flange.

While installing a toilet from scratch, the drainpipe will be protruding up about 5 inches from the floor. You will therefore need to cut it flush off the floor. Ideally, the toilet flange should be ¼ inch above the bathroom floor.

Modern drainpipes are made of PVC which is really easy to cut. Old toilets had a Cast iron drainpipe which was really hard to cut off.


Here is how to install a toilet flange.

  • Measure the distance from the floor to the top of the drainpipe.
  • Put your internal pipe cutter into the drilling machine and adjust the height to that measured above.
  • Cut the the drainpipe cleanly all around from the inside of the pipe.
  • If you don’t have a drilling machine and/or an internal pipe cutter, use a saw to nicely cut the pipe off. This might be a little harder but not impossible.
  • Use an emery cloth or putty knife to clean inside and around the drainpipe.
  • Try fitting the flange on the drainpipe and see if it fits perfectly.
  • Toilet flanges must be installed in a certain orientation. To do this effectively, imagine the flange is a wall clock. The toilet bolts will need to precisely be on the 3 and 9 clock positions. The flange has two rectangular slots. You just put the head of the bolts through these slots then push them to the end of the narrow sections.
  • Once you have established that the flange is fitting well, remove it apply glue on it as well as well as the drainpipe.
  • Put it back in the drainpipe and align it properly.
  • Slide in the toilet bolts and move them to the narrow ends of the flange slots.
  • Put a washer on top of each bolt.
  • The flange will need to be screwed down to the floor using 3/4 screw. Use the drilling machine to screw it into place.

Step 3: How to Install a Wax Ring

  • Some people will prefer to set the wax ring on top of the flange then install the toilet straight on it.
  • A better and sure way to do it is to tilt the toilet or to lay it gently on its side and set the wax ring on the toilet outlet. This way you will be sure your wax ring will not shit during installation.
  • If you decide to use a rubber gasket seal, you will set it straight on the flange then install the toilet. Some rubber gasket seals have 2 holes which you slot in the toilet bolts to prevent them from shifting while installing a toilet.

Step 4: How to Install a Toilet Bowl

If you are installing a one-piece toilet, you will install the bowl and the tank together. With a two-piece toilet you will install the tank later.

  • Lift off the toilet bowl and bring it above the flange.
  • Lower the toilet gently to align the holes at the base to the toilet bolts.
  • When aligned, put the toilet down gently.
  • Hold the bowl with both hands, press it down while rocking it a bit to fully engage the wax ring.
  • Put a washer and nut on each bolt and hand tighten until snug. Use the adjustable wrench to tighten the bolts alternatingly to keep the toilet level. Do not however tighten it too much lest you crack the bowl.
  • Cut off the protruding ends of the toilet bolts and cap them off

Step 5: How to Install a Toilet Tank

A toilet tank is joint to the bowl using 2 and sometimes 3 bolts. The bolts normally comes preinstalled on the tank and you will only need to install and tighten it on the bowl.

  • Install the toilet tank to bowl gasket. This gasket is installed at the bottom of the toilet tank and around the flush valve. It prevents the toilet tank from leaking where it is joint to the tank during flushing. Making sure that the gasket completely covers the flush valve lock nut. A toilet tank to bowl gasket is sometimes referred to as a spud washer.
  • Lift off the toilet tank and mount it on top of the bowl. You will now need to tighten it from underneath the toilet bowl.
  • On the protruding bolts underneath the bowl, put in a rubber washer, steel washer and a nut. Hand tight until snug.
  • Use a wrench to tighten the two bolts alternatingly to keep the tank level on the bowl. Again, do not tighten too much to avoid cracking the bowl.
  • Look inside the tank and make sure the valves are all in position. Fix the flapper properly on top of the flush valve opening.
  • Connect the water supply line from the shut off valve to the toilet tank. The coupling that connects to the tank should only be hand tight. Using a wrench on it may deform it.

Step 6: Test the New Toilet.

  • Turn on the water supply and the let the toilet tank fill with water.
  • Flush the toilet a couple of times.
  • Check for leaks at the base of the toilet and also between the bowl and the tank.
  • When everything stays dry then you have successfully installed a toilet from scratch.
  • Put the toilet tank lid on top of the tank.

Step 7: How to Install a Toilet Seat


Most toilets are sold without toilet seats you are therefore forced to buy one separately. All toilet seats are not designed the same so installing them will also be different.

For a basic toilet seat this is how to install it. If you have a soft close toilet seat whether top fixing or bottom fixing, this is how to install it.

Step 8: Caulk the Toilet

Some people prefer to caulk the toilet while others don’t like it at all. The decision ultimately comes down to the homeowner’s preference.

If you want to know why should caulk around your toilet check out this post.