Q: We have a toilet with an intermittent floor leak that a double wax ring and a new toilet could not correct. The toilet sits on a slightly uneven slab floor. There hasn’t been a leak the 50 years we have lived here. Any ideas?
A: The most likely cause is that the wax ring around the closet flange is leaking, allowing a small amount of water to seep from under the toilet with each flush. The wax rings are probably misaligned.
The fix is to reset the toilet using a flange extension and one wax ring. The slight unevenness of the slab might be a contributing factor, but you can fix that by shimming the bottom of the toilet so that it sits level.
Toilet hydraulics are pretty simple. Waste and wastewater are discharged from the toilet bowl through an S curve in the bowl structure into a waste pipe. The toilet bowl is bolted to the floor with closet bolts attached to a flange connected to the waste pipe.
A wax ring, when correctly installed, produces a watertight seal between discharge hole and the waste pipe. If the closet flange sits below the level of the finished floor or the wax ring is installed catawampus, the seal can be incomplete, and the toilet will leak.
Removing and resetting the toilet properly will stop the leak.
To remove the toilet:
1. Shut off the water to the tank.
2. Flush the toilet to empty the tank.
3. Remove the remaining water in the tank with a small cup.
4. Use a sponge to remove the rest. Next, disconnect the line running from the water supply valve to the tank.
5. Unscrew the two bolts securing the tank to the bowl and lift the tank off the bowl and set it carefully aside. (This assumes you have a two-piece toilet. If you have a one-piece toilet, there are no tank bolts and you will have to remove the entire fixture.)
6. Remove the bowl (or entire fixture) from the floor. To do this, remove the caps covering the closet bolts on the base of the toilet. Unscrew the nuts from the closet bolts.
7. If there is caulk or putty around the base of the bowl, score it with a putty knife.
8. Gently rock the bowl side-to-side and front to back to loosen the bowl. When the bowl is loose, lift it off. Water will remain in the toilet trap inside the bowl. Some of it will end up on the floor. Have a rag, mop or sponge ready.
To reset the toilet, the basic steps are:
1. Clean the wax off the discharge hole and flange.
2. Install a flange extension if the existing flange is below the finished floor level. A flange extension is essentially a large washer that bolts to the existing flange to raise the height of the toilet flange.
3. Replace the toilet bolts and wax ring.
4. Set and level the bowl.
4. Reinstall the tank on the bowl.
5. Connect the water supply and test for any leaks by flushing several times.
In more detail:
1. Place a new wax ring on the discharge hole on the bottom of the bowl. Buy one with a plastic extension that fits into the waste pipe.
2. Most toilet-bolt kits come with some kind of press-on plastic pieces that are supposed to temporarily hold the bolts upright when setting the toilet. Throw them away and use another set of nuts and washers to secure the bolts to the flange before installing the toilet. This will hold the bolts firmly while you jiggle the toilet onto them.
3. Jiggle the bowl onto the flange by pressing strongly on the edges of the bowl to make sure the wax ring is fully compressed. If you see a little wax in the bolt holes that’s OK.
4. Level the bowl, front to back and side to side, using a spirit level. Use wood shims to elevate the edges of the bowl if needed. Install the shims with the narrow end pointing toward the center of the toilet so that they support only one point; break the shim to approximately the correct length so that not too much pokes under the toilet.
5. Install the plastic cap washer, the steel washer and the nut onto each bolt and tighten evenly. Don’t be a gorilla. On many marginal plumbing installations it’s possible to pull the toilet flange up out of the floor.
5. Next, reinstall the tank. Make sure to use a new rubber washer for the connection between the tank and the bowl.
6. Test the toilet again for wobble and add or adjust the shims slightly if needed.
7. Tighten the bolts a quarter turn more, connect the water supply and test it with five or six flushes to be sure water doesn’t show up on the floor.
8. Use the point of a new utility-knife blade to cut the shims right at the base of the toilet.
9. Caulk the joint where the toilet meets the floor, leaving about 4 inches at the back of the toilet clear so you’ll know if a future leak develops. Caulk serves a couple of purposes. Most important, it keeps the shims in place. It also hides the shims, and it adds a little extra "glue" to keep the toilet in place. Because caulk shrinks when it dries, you may need to do it again the next day.
Follow these steps and we’re confident your leak will be a thing of the past.