Why Does My Toilet Keep Running? Causes and Fixes

How a Toilet Tank Works, in Thirty Seconds

Lift the lid off the tank and you will see two main parts. On one side is the fill valve, the tall assembly that lets water in after a flush. In the middle or on the other side is the flush valve, with a rubber flapper at the bottom that lifts when you push the handle and drops back down to seal the tank.

A running toilet means water is going somewhere it should not. Either it is leaking past the flapper into the bowl, or the tank is overfilling and spilling down the overflow tube, the open pipe in the middle of the flush valve. Every cause below is one of those two problems, and figuring out which one you have tells you which part to replace.

The Four Most Common Causes of a Running Toilet

In our experience across Portsmouth, Chesapeake, Norfolk, and Virginia Beach, nearly every running toilet comes down to one of these:

• A worn or warped flapper. Rubber hardens and loses its shape over a few years, and chlorinated city water and in-tank cleaning tablets speed that up. Once it stops sealing, water trickles into the bowl and the tank refills on its own every so often. This is the cause more often than all the others combined.
• A chain that is the wrong length. Too short and it holds the flapper slightly open. Too long and the slack gets trapped under the flapper when it drops. You want about half an inch of slack.
• A fill valve set too high or failing. If the water level climbs above the top of the overflow tube, it spills down it constantly. An older fill valve can also stop shutting off cleanly and hiss as it lets water through.
• Mineral buildup or a damaged flush valve seat. If the flapper is new and still leaks, the ring it seals against may be pitted, cracked, or crusted with scale, and no flapper will seal on a rough seat.

How Much Water Does a Running Toilet Waste?

More than most people expect. The EPA's WaterSense program estimates that a leaking toilet can waste around 200 gallons a day. A slow, silent leak past the flapper wastes less, but because it runs every hour of every day, it still adds up to thousands of gallons over a billing cycle.

That is why a running toilet is often discovered on the water bill rather than by ear. If your bill jumps and nothing else in the house has changed, check the toilets before anything else. Put a few drops of food coloring in the tank, leave it for fifteen minutes without flushing, and look in the bowl. Color in the bowl means water is getting past the flapper.

If the toilets pass that test and the bill is still high, the water is going somewhere you cannot see, under the slab, inside a wall, or in the line out to the street. Our guide to the hidden water leak signs Hampton Roads homeowners miss covers what to check next.

How to Fix a Running Toilet Yourself

Start with the cheapest and most likely fix, and work your way up. Turn off the supply valve behind the toilet and flush to empty the tank before you change any part.

• Adjust the chain first. Hook it so there is a little slack with the flapper closed. It costs nothing and fixes more toilets than you would think.
• Lower the water level. Turn the adjustment screw or slide the clip on the fill valve until the water stops about an inch below the top of the overflow tube.
• Replace the flapper. Take the old one to the hardware store so you match the size. Most are 2 inches, but many newer toilets use 3-inch flush valves, and the wrong flapper will never seal.
• Replace the fill valve. A universal fill valve kit is inexpensive, fits most toilets, and takes about twenty minutes with a sponge and an adjustable wrench.

When a Running Toilet Needs a Plumber

Call a plumber if the shutoff valve behind the toilet will not turn or starts leaking when you touch it, if a new flapper and fill valve did not stop the problem, if the tank is cracked, or if you see water on the floor around the base. A running toilet wastes water. A toilet leaking at the base rots the subfloor, and that turns a small repair into a floor repair.

Older homes in Portsmouth and Norfolk often have original shutoff valves that have not been turned in decades. Forcing one can snap the stem and leave you with water spraying behind the toilet and no way to stop it short of the main. If that valve looks corroded, it is worth having us replace it during the same visit.

Sometimes the honest answer is that the toilet itself is the problem. A worn-out flush valve seat on an older toilet can cost nearly as much to repair as a new, efficient toilet costs to install. Our residential plumbing service covers toilet repair and replacement, and we will tell you which one makes sense before any work starts. Call (757) 465-0883 and we can usually get you on the schedule the same day.