How to Hook Up the Toilet Drain to an Existing Drain

Soil Pipe Connection

• The drainpipe in the floor that you connect the toilet’s drain to is called a soil pipe. You must use a closet flange to establish a connection with the soil pipe. The closet flange has a PVC collar that fits inside the soil pipe opening, which you must cut enough that the closet flange rests on the bathroom floor. The flange must be anchored to the floor with screws. If the flange is not mounted tightly against the bathroom floor so it cannot shift in any direction, water will leak between the toilet and bathroom floor.

Preparation for Mounting

• With the closet flange in place, you must set up various parts before you can place the toilet on the flange. The closet bolts fit in the slots on the flange, with the bolt heads inserted inside the flange. Placing washers over the closet bolts helps protect the flange from future damage as you mount the toilet. You also need to place a fresh wax ring either on the flange or press it onto the underside of the toilet, around its drain opening. Whichever method you choose, the rounded side of the wax ring must touch the toilet and not the flange.

Mounting the Toilet

• When you lower the toilet onto the flange, your first concern is that the closet bolts have to line up with the holes in the toilet’s base. Once you rest the toilet on the flange, you will notice that the toilet’s base does not touch the bathroom floor all the way around. You must press down on the bowl to compact the wax ring, helping create a watertight seal. You may sit on the toilet bowl to compress the wax ring, but you cannot twist or move the bowl. Keep pressing on the bowl while you tighten the nuts on the ends of the closet bolts. If you over-tighten the nuts, you can crack the bowl.

Finishing Touches

• The toilet should come with some plastic dome pieces that fit over the closet bolts and nuts on the base of the toilet. The closet bolts are likely too long to fit the caps over them, which is why you must cut them down with a close-quarters hacksaw. Leave three threads on the bolts that are exposed above the nuts. You must also thread the ends of the flexible water supply hose onto the threaded opening on the underside of the toilet tank, and onto the threaded opening on the water supply valve on the bathroom wall. Once you tighten the water supply connections, you are ready to turn the water supply valve’s handle counterclockwise, which fills the toilet with water.