How to Repair a Leaking Toilet

In this video, Ask This Old House plumbing and heating expert Richard Trethewey explains what may be causing a leaky toilet and possible solutions.

Steps:

1. To diagnose a leak, check out a few places on the toilet.
2. First check out the water supply line. It’s possible there could be a loose nut or a leak on the supply hose.
3. Next check the line between the tank and the bowl. Bolts may be loose, causing the leak to appear just below the tank.
4. If the leak is most prominent on the floor around the toilet (or on the ceiling below), check the wax ring seal between the toilet and the flange.
5. If the height of the flange is too low, you may have to get a higher wax ring to compensate.
6. Alternatives to the wax ring are a foam seal or a plastic seal.
7. Other options for raising the flange: Adding flange spacers or adding a flange insert.

Pro Tip: Richard Trethewey, This Old House plumbing and heating expert, advises a hands-on approach to finding the source: “Leaks can be tricky. You’ve just got to put your head down there and see what’s going on.” He suggests drying everything off, grabbing a flashlight, and getting on hands and knees after a half-dozen flushings to pinpoint exactly where the water is coming from.

Because water beneath the toilet can severely damage the underlying subfloor and joists, avoid caulking around the base of the toilet as a fix. Caulk can actually mask an active leak, trapping water underneath where it continues to cause hidden damage. Instead, pull the toilet and install a new wax ring to properly address the seal.