Updated Sept. 29, 2017.

To install a toilet, you have to begin with the plumbing. We’ll take you through the steps of roughing in the pipes. If you have any problems, give us a call. We’re a locally-owned Portland plumbing company with years of experience and a commitment to our customers.


Before installing a toilet, you need to run the waste drain and supply lines to the location of the new toilet. Follow the toilet’s supply and drainage requirements to install the acrylonitrite butadiene styrene (ABS) drainage pipes and copper supply lines. If you are unsure how to properly install these pipes, it’s crucial that you hire a professional plumber. A mistake here will likely make it impossible to install a new toilet until done correctly.

Water Supply Line

  1. Turn off your home’s water supply by closing the main service valve. In most houses around Portland, you can find this valve in a concrete box close to the street. Learn more about the various shutoff valves in and around your house.
  2. Install a ½ inch copper water line to the location of your new toilet. Insert the line through the bottom plate on the wall, approximately 8 inches to the left of the toilet’s center line. Connect this supply line at the water line attached to the sink. Use a 90-degree elbow or stub-out fitting to insert the water line into the surface plane of the wall. Be sure to make it parallel to and 8 inches above the floor surface.
  3. Find an adjacent wall stud and secure the copper water piping to it with an insulated pipe hook. One alternative is to solder the line to a copper nailing strap that is secured to the wall studs on either side of the water line.

Toilet Stop Valvemain-water-line-repair-portland

Install your toilet stop valve and a trim ring to the end of a ½-inch copper water line stub-out. Trim the copper pipe beforehand. The stop valve should be as close to flush as possible with the surface of the wall.

Waste Drain

  1. Connect an ABS drain, 4 inches in diameter, to the main waste drain line near the toilet. Extend the new drain line to the toilet location. If you are remodeling and the new toilet location is part of an added full bathroom, you can tie the sink and bathtub drainage into the toilet waste drain. Allow for the minimum slope required by your building code. Install a clean-out fitting at the point where the waste drain lines becomes vertical and meets the bathroom floor.
  2. Cut a hole with a 6-inch diameter in the surface of the bathroom subfloor. Make sure to check that the location of the waste drain matches the manufacturer’s guidelines for the toilet.
  3. Look for the finished end of the ABS piping as centered through the subfloor, approximately 12 inches from the rear wall of your bathroom, flush with the surface of the subfloor. Allow 18 inches minimum on either side from the wall of the cabinet.

A Portland plumber working in a bathroomFinishing Steps

  1. Create support beneath the subfloor for the drain line with standard ABS strapping. You can also use blocks to hold the drain pipe in the correct position.
  2. Install the toilet flange to the ABS waste drain pipe. Attach the flange to the subfloor with plated wood screws. Your supply and drain lines are now complete and ready for the new toilet.

Portland has a reputation for doing things its own way, but when it comes to plumbing, it’s a good bet that we swing the same way as the majority of Oregonians: we like having toilets.

In the most recent U.S. Census Bureau data, an estimated 1.6 million people in the nation are living without full indoor plumbing. That’s a sorry state of affairs. We’re here to help our Portland neighbors who are without toilets by outlining how to rough-in toilet plumbing.

Prepping your bathroom for a new toilet need not be a source of stress. If after reading these instructions, you don’t want to rough-in toilet plumbing yourself, contact Meticulous Plumbing. We’re happy to help out.

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