The two most common reasons for toilet leakage are faulty supply lines and worn wax rings. Both can be fixed with common household tools and a little know-how.
Step 1: Soak up existing water Soak up standing water around the toilet with a towel. Wait half an hour to determine whether the water is coming from beneath the toilet or from the water supply line on the bottom of your toilet tank.
Step 2: Remove old supply line Replace the supply line if the water is leaking from your existing supply line. Turn the water off by closing the shutoff valve and flush the toilet to remove most of the water. Use a wrench to disconnect the hex nuts that connect the old supply line to the shutoff valve and to the toilet tank.
Step 3: Install new supply line Attach the wide, conical end of a plastic replacement supply line into the shutoff valve and replace the hex nut. Then slide the brass compression nut over the tube, with the open end facing the toilet tank, followed by the plastic compression ring, tapered side up. Use your utility knife to cut the line to size and reattach the nut to the toilet tank, tightening it with your wrench.
TIP: You can also use a braided stainless steel supply line. They're flexible and the connecting nuts are already attached, but they're only available in set lengths.
Step 4: Remove hex nuts Replace your wax ring if the leak is coming from under the toilet's base. Turn off the water supply and flush the toilet to get rid of most of the water. Then remove the hex nuts from either side of the base.
Step 5: Remove the old wax ring Lift the toilet free of the closet bolts, turn it over, and use the putty knife to scrape away the old wax ring. Make sure you scrape any residual wax from the flange, too.
TIP: You might want to use mineral spirits to thoroughly clean away the old wax. You want a clean surface to attach the new wax ring.
Step 6: Attach the new wax ring Firmly press the new wax ring either onto the flange in the floor or onto the base of the toilet. Then place the toilet back onto the closet bolts, replace and hand-tighten the hex nuts, and sit on the toilet (with the lid closed, of course). Rock back and forth to spread the wax and close the seal. Finally, tighten the nuts with a wrench, being careful not to use too much torque and crack your toilet. Now your bathroom is leak free.
FACT: According to the EPA, if Americans replaced old toilets with new, water-efficient models, it could save nearly 2 billion gallons of water per day.