Lead was a common material used in residential and commercial plumbing applications in the past. It was replaced by PVC and other plumbing materials because of its toxicity. When refurbishing an old house, particularly the bathroom, you may encounter a lead waste or soil pipe when installing a new toilet. Rather than leave the lead waste pipe in place, you can switch it out with a new soil pipe.
Turn off the water supply to the bathroom if possible, or the main water supply to the house. Take the lid off the toilet tank and then flush the toilet. Scoop out any remaining water with a cup.
Unfasten the coupling on the water supply hose leading to the toilet either by hand or with a wrench. Next, unfasten the nuts under the tank to free the tank from the base. Gently pull the tank off the base and place it in the bathtub or shower.
Loosen the bolts on either side of the toilet base. Slide a putty knife between the base of the toilet and the floor. Begin to score around the base of the toilet to loosen it from where it sits. Next, begin to turn the toilet bowl from side to side to free it from the floor. Once it's free, place it next to the tank in the shower or bathtub, if possible.
Scrape away the old wax ring, as well as any grime that may have accumulated under the base of the toilet since it was first installed. Clean the flange bolts with a wire brush at this point as well.
Put on gloves, safety glasses and a dust mask. Cut out the old waste or soil pipe, using a soil pipe cutter. This will require some trial and error before you can successfully cut out the old lead pipe. Place a compression collar on the section of old waste pipe that remains below the floor's surface. Insert a cast iron pipe into the compression collar and tighten the collar with a wrench.
Put a new wax ring on the floor around the waste pipe where the old wax ring was located. Set the toilet base on the flanges over the wax ring, and tighten the bolts on the toilet's base. Next, replace the tank, securing it by tightening the bolts on the underside.
Spread pipe thread compound in the water supply hose's threads, using the cap brush supplied in the compound can. Refasten the water supply to the tank, tightening it in place with a wrench. Turn the water supply back on and let the tank fill with water. Flush the toilet, and watch the base to make sure no leaks seep from under the base onto the floor.