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How to Install a Toilet on Lead Pipe

Updated July 18, 2017

You never know what you might find when you start tearing apart the walls and floors in an old home. One of the surprises that really causes do-it-yourselfers to scratch their heads is when they discover a lead pipe sewer line hiding under the house or in a crawlspace. The challenge lies in joining the new plumbing fixtures to the old lead pipe, and nowhere is that challenge more apparent than when you are installing a new toilet.

Tear open the subfloor, if necessary, to expose the top of the lead pipe. Measure the distance from the top of the lead pipe to a point 1 inch below the floor surface.

Cut a length of 4-inch PVC pipe, using the same distance you just measured. Attach PVC pipe to the lead pipe with a rubber flange, by tightening the clamp screws on the flange.

Prime the top of the PVC pipe and the bottom inside of the PVC toilet flange with primer. Glue the PVC toilet flange to the top of the PVC pipe. Replace the flooring (if you tore it out) with hammer and nails.

Slide the 2 toilet mounting bolts into the slots in the flange. Press a wax seal on the toilet flange, according to attached instructions. Set the toilet onto the flange and secure the toilet to the flange bolts with washers and nuts. Attach the water supply hose.

Tear open the subfloor, if necessary, to expose the top of the lead pipe. Cut the lead pipe to 1 inch below the floor surface, if it is higher than that. Press the instant set closet flange onto the lead pipe.

Tighten the rubber gasket on the instant set closet flange by screwing the exposed screws clockwise. (Refer to the specific instructions for the instant set closet flange you purchased.)

Replace the flooring (if you tore it out) with hammer and nails. Slide the 2 toilet mounting bolts into the slots in the flange. Press a wax seal on the toilet flange, according to attached instructions. Set the toilet onto the flange and secure the toilet to the flange bolts with washers and nuts. Attach the water supply hose.

Things You'll Need

  • Crowbar
  • Tape measure
  • 4-inch PVC pipe
  • Hacksaw
  • 4-inch rubber flange (Fernco)
  • Screwdriver
  • 4- by 2-inch PVC toilet flange
  • PVC primer
  • PVC cement
  • Hammer
  • Nails
  • Toilet mounting bolts and nuts
  • Washers
  • Wax toilet seal
  • 4- by 2-inch instant set closet flange
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About the Author

James Werning has authored books and articles on various websites. His scripts have aired for more than 15 years on radio stations across North America. He is a small business owner and a world traveler with a master's degree in communications from the University of Edinburgh, Scotland.