by Murray Anderson
Here’s a step by step outline of a rough in for a toilet installation. Bear in mind that each situation is slightly different so this only provides a basic outline and list of considerations.
Rough in plumbing for a toilet.
- Determine where the toilet is going to be positioned and mark its center on the wall. Measure out 13 ½ inches and mark the location, this is where the closet flange will be located.
- Center the flange on top of the mark and draw a line around the outside of it. You need to cut this section out and position the flange in the hole with the edges sitting solidly on the floor. Ensure the two elongated slots are on the sides (your toilet bowl bolts onto the flange using these two slots) and screw the flange to the floor. Since the closet flange needs to be flush with the finished floor, you may need to put shims under the flange before bolting it to the floor if your are going to be using a raised floor (like ceramic tile).
- Underneath the floor you install your drain and vent components. You want to direct the flow towards the main waste stack. Use a 3” long turn 90 degree fitting and run it into a 3” x 3” x 2” Y fitting positioned so the 2” lead can be piped back to the main vent pipe. Continue the 3” piping to the main waste stack and connect into it with a 3” Y fitting.
To install the water supply line run the water supply directly up through the floor or inside the wall near the side of the toilet tank that has the water supply link fixture on it.
- Position a “T” fitting on top of the supply line, with the water line going into the bottom of the “T”, the middle outlet of the “T’ facing out through the wall and the top of the “T” extending up in behind the wall.
- Attach an 8 “ section of section pipe extending through the wall to supply the toilet and attach a piece of pipe (about 12” long) onto this up pointing ‘T’ side. Solder or attach cap fitting to this section to create an air chamber that will prevent ‘water hammer’.
Some important considerations when you’re installing plumbing
Slope matters
- The ideal slope for a drain is ¼” per foot. Too little slope means water (and solids) may not drain while too much slope could cause the water to drain away too fast, leaving solids behind and you can end up with clogged pipes.
- Proper angles on vent pipes are necessary
- Vents need to angle upwards at a 45-degree angle or more away from level to ensure they won’t ever fill with water. A vent filled with water obviously can’t work
- Accessible clean outs are required
- Local plumbing codes specify where clean outs are required in a plumbing system. No matter how well a system is designed and built, clogs can occur and you need to be able open up the drain and clean it out manually.
- People need space
- For someone to comfortably use a toilet, a minimum of 15 inches from the center of a toilet to a wall or vanity on either side as well as 18” from the front of a toilet to the facing wall should be provided.
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Questions of a Do It Yourself nature should be submitted to our
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Hello, I've got a toilet drain right in the center of a small bathroom. I've taken out some walls and would like to move the toilet about 5 to 6' from the existing riser. I took out the cast iron pipe and have a 4" bell in the crawl space about 2' below the floor. I'm wanting to put the toilet at 2 o'clock with the drain coming in at 12 o'clock. So I'd be going toward the direction of travel with the new location of the toilet. The new drain would tie into the existing drain almost over the top of it and be turning back almost 180 degrees to flow the other direction. Can that be done? How do I tie into the old drain? What do I use? Thanks for any help you can give me,Tim