How to Install a New Toilet

Modern dual-flush toilets can help offset the investment over time by reducing water usage. As demonstrated on a This Old House installation, these models offer two flush settings—typically 0.9 gallons per flush for liquids and 1.6 gallons for solids—and often feature a cleaner, more contemporary design with no exposed closet bolts.

In this video, This Old House plumbing and heating expert Richard Trethewey heads to Cheyenne, Wyoming, to help a homeowner install a new toilet.

When setting the wax ring, keep in mind that it serves a critical dual purpose. As explained during the installation, the wax ring seals “against sewer gas leaking out or water leaving the bottom of the toilet.” Press the wax ring firmly onto the closet flange before positioning the toilet, and make sure the closet bolts are parallel to the back wall for a proper fit.

Steps:

1. Turn off the water at the meter.

2. Open all faucets on the upper level of the house, then open the tub or shower valve in the bathroom where you’re installing the toilet.

3. Use emery cloth to buff clean the copper pipe stub-out protruding from the wall.

4. Put a shallow pan or a small bucket under the pipe stub-out to catch any water.

5. Use a tubing cutter to cut the pipe stub-out to the proper length.

6. Slip a new shutoff valve onto the pipe stub-out, then tighten the compression fitting with two adjustable wrenches.

7. Close all the faucets and valves opened in Step 2.

8. Turn the water back on at the meter.

9. Temporarily plug the toilet’s PVC drainpipe with a rag to block out sewer gases.

10. Trim the PVC drainpipe to the proper height using a drill/driver fitted with an internal pipe cutter.

11. Use a hammer and a cold chisel to chip away any excess thinset mortar from around drainpipe.

12. Glue a new closet flange onto the drainpipe with PVC primer and cement, then insert two closet bolts into the slots in the flange.

13. Drill through the mounting holes in the flange and into the ceramic tile with a carbide-tip masonry bit.

14. Secure the flange to the floor with masonry screws.

15. Bolt the toilet tank to the toilet bowl, making sure to install the included rubber gasket between the two parts.

16. Attach the toilet seat to the toilet bowl with the two included plastic bolts.

17. Press a wax toilet ring onto the closet flange, then remove the rag from the drainpipe.

18. Set the toilet over the closet bolts protruding from the flange. Press down on the toilet to compress the wax ring.

19. Place the washers and nuts onto each closet bolt and alternately tighten each nut with a wrench. Do not overtighten the nuts.

20. Use a mini hacksaw to trim each bolt.

21. Snap the included plastic cap onto each closet bolt.

22. Tighten one end of a stainless-steel water-supply line to the shutoff valve. Connect the other end to the fitting on the underside of the toilet tank.

23. Open the shutoff valve to fill the toilet tank with water.

24. Put the lid on the tank, then flush the toilet to check your work.

Pro Tip: When tightening the closet bolts that secure the toilet to the flange, work gradually — tighten each bolt a little bit at a time rather than fully tightening one side first. As demonstrated during the project, this ensures the rubber gasket compresses evenly and the toilet seats squarely on the wax ring. Over-tightening can crack the porcelain base, so use a hand wrench rather than a power drill for final tightening.

Pro Tip: Richard Trethewey, This Old House plumbing and heating expert, emphasizes the importance of individual shutoff valves: “Any plumbing fixture should have a separate service shut off.” Installing a dedicated shutoff valve on the supply line ensures you can service the toilet in the future without cutting water to the entire house.