How to install plumbing for toilet pipes

Updated February 21, 2017

When adding a new toilet or perhaps a second toilet, you'll need to know how to plumb in the toilet pipes. Most homes already have a plumbing main stack in the wall, so all you need is to connect your toilet to that stack. This job is not difficult and can be completed in just a few hours on a weekend day.

Cut out the drywall where the plumbing stack pipe is located. Use a drywall knife. Cut out a section that is stud to stud, about 16 or 24 inches wide and about 2 feet high.

Inspect the stack to see what kind of material the pipe is made of. Concrete, cast and clay pipe can all be cut the same way. Plastic pipe will be cut differently.

Position a 4-inch no-hub wye up against the plumbing stack pipe where you will make your cut. Mark the location of the wye fitting with a marking pen, so you can make your cut in the plumbing stack pipe.

Cut out a section of the concrete, cast or clay pipe with a sawzall.

Place the no-hub fitting over the section of cut-out stack pipe and tighten down the hose clamps on each side with a screwdriver.

Measure 12 inches from the wall out toward the bathroom. The centre of the 12 inches will be the centre of the toilet drain. Mark the location on the exposed floor with a marking pen.

Install the toilet drain slightly below the floor level. Attach it to the floor with drywall screws or nails. This will depend on what kind of floor you have. Use screws for wood floors or concrete nails for concrete floors. Use a hammer or cordless drill with screw bits.

Attach a long 4-inch sweep loosely to the bottom of the toilet drain. Then cut a piece of 4-inch ABS pipe with a hacksaw to connect the no-hub fitting to the rest of the toilet drain you just laid. Dry-fit everything for now, before you do any gluing.

Disconnect the dry fittings once they are fitted properly.

Put ABS cleaner on each ABS fitting, both on the inside and outside. Do the same with the glue. Attach and glue each piece from the toilet drain to the drain stack. Slide the last piece of ABS pipe into the no-hub fitting and tighten down on the last hose clamp.


Wear eye protection, gloves, kneepads and ear protection.

Things You'll Need

  • Drywall knife
  • No-hub wye
  • Marking pen
  • Sawzall
  • Extension cord
  • Screwdriver
  • Concrete nails
  • Cordless drill
  • Screw bits
  • Drywall screws
  • 4-inch ABS sweep
  • Hacksaw
  • 4 feet of 4-inch ABS pipe
  • ABS cleaner
  • ABS glue
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About the Author

Joey Pellham has three years experience teaching writing courses in China. He specializes in home improvement/do it yourself and parenting articles. He has written for publications such as Associated Content, Triond, Wordpress, and Blog Spot. Pellham has been freelance writing since 2008. Pellham studied at Washington State University.