A common place to find lead is in an older home that uses a lead toilet riser. The bottom end of the lead riser is bonded to a cast-iron insert, which is fit into the elbow of a cast-iron waste pipe. A cast-iron closet flange is on top of the lead riser. Lead is soft and easy to cut through but also becomes brittle with age. Therefore, when you are removing one toilet and replacing it with another and you find these lead fittings, you should replace them.
Remove the riser and the flange attached to it. Cut the lead riser, using the hacksaw, where it meets the cast-iron insert. Install a 4-by-3-inch banded coupling on the insert.
Install a PVC pipe, of 3-inch diameter, from the top of the coupling. Cut the PVC pipe flush with the floor, using the hacksaw. Wipe PVC primer onto the top edge of the pipe and on the inside of the replacement closet flange. Apply PVC cement onto the top edge of the pipe and the inside of the replacement closet flange. Twist and press the closet flange onto the pipe until the collar seats on the floor. Drill stainless-steel screws through the flange holes, far enough into the floor to bite into the subfloor. This secures the flange to the floor.
Insert two new closet bolts, with the threaded ends up, into the slots in the flange. Position the bolts so that they are parallel to the wall behind the flange. Slip a brass washer, included with the bolts, over each bolt. Invert the new toilet bowl and press the new wax ring into place on the toilet horn, which is the discharge outlet on the bowl's bottom. If you prefer, place the wax ring on top of the flange so that the ring's flat side faces down.
Lift the toilet bowl over the flange. Carefully lower the bowl onto the flange so that the closet bolts pass through the holes in the base of the bowl. Sit on the bowl to press it down onto the wax ring. Install a plastic retainer, a washer and a nut, included with the flange bolts, onto each bolt. Alternately and evenly tighten the nuts, 1/4 turn at a time, using an adjustable wrench. Stop when the wrench encounters firm resistance, and avoid over-tightening. Cut the closet bolts two threads above the top of the nuts, and snap on the bolt covers.
Install the rubber tank washers into holes in the bottom of the replacement tank. Install the two tank-to-bowl bolts through the washers and holes. Gently lift and lower the tank onto the bowl, guiding the bolts through the corresponding holes in the bowl. Install a metal washer and nut on each bolt from underneath. Hold the bolt in place with a slotted screwdriver inside the tank, while tightening the nuts underneath by hand.
Connect the supply line to the tank, tightening the nut 1/4 turn past hand tight. Position the seat on the bowl. Install bolts through the seat holes and install and tighten nuts onto the bolts from underneath, by hand. Turn on the water supply and check for leaks as the tank fills. Flush the toilet and check for any leaks.