How to Plumb a Toilet

Many people know how a toilet works. What they don’t know is how to put the toilet together when bought from the store to the moment it can be used. In this post I am going to show you how to set up your toilet, assemble the toilet pieces, and also join up the drain system until you can use your toilet.

What You Must Know

Your toilet’s waste system starts from the toilet’s waste outlet. While that of the main pipe starts from the soil stack. The stack is pipe that drops 3 or 4 inches vertically and is usually connected to a 2” pipe rising above the roof for venting.

To connect your new toilet you need three main fittings. The first fitting will hold the toilet down and give it the perfect seals. The second one directs water flow to the stack while the last one ties your toilet on the stack.

Plumbing Your Toilet

With these two facts in mind, you can go ahead and plumb your toilet. To do that you should follow these smart steps.

#1: Determine the Location of the Hole

Use a tape measure to measure the size of your walls. Then determine the toilet’s rough in. For many modern toilets, the toilet hole should be at about 12” from the chosen back wall and also one of the remaining side walls.

#2: Cut Out the Hole- Use Reciprocating Saw

Many toilet use a toilet hole of about 3” in diameter. This is ideal for 3” waste pipes. Nonetheless your toilet hole may need an additional inch if you have to get the best fit. But that depends on the toilet model that you have chosen and its distance from the stack.

#3: Install a Toilet Flange

Toilet flange will come as a complete set that you can fix straight up or assemble first. To install your flange first insert a pipe through the hole on the floor. Then set a plastic ring or metal on your sub floor. Make sure the ring flushes with the surface of the floor before you bolt your flange to the sub-floor.

Identify the PVC closet bend (the 90 degree wide-sweep elbow) used when installing a toilet and dry fit it to the flange pipe.

#4: Mark for the Perfect Slope

Take the measurement of the closet outlet bend and the soil stack. Use spirit level and tape measure and put a mark on the stack. The mark should give the waste pipe a 1/4 inch per foot slope towards the stack.

Example: If the main distance between the closets outlet bend and your stack sits at 6 feet; your mark must stand at about 1 1/2 inches below the upper part of the bend’s outlet.

#5: Cut Through the Mark on the Stack

Use your handsaw to cut through the mark on the stack. Then insert a sanitary tee. Make sure the tee has its inlet facing the toilet. Every sanitary tee will have a sweep inlet and not a straight one. Ensure that the sweep faces down.

#6: Dry fit PVC Pipe between the Bend and Tee

Use your handsaw and cut a 3-inch PVC pipe. Make sure the pipe has an equal length as the distance between the main bend outlet and tee inlet (plus an extra 2 inches). Dry fit this PVC pipe between the bend and tee.


Once you are sure that every measurement fits, you should disassemble all parts that you had previously assembled through dry fitting and then use PVC cement to re-assemble them.  You should make sure the slope is perfect.

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