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What Causes Toilets to Keep Running?

Sometimes trouble comes in a trickle instead of a flood. That’s certainly the case with a constantly running toilet, which can drive up your water bills even as it’s driving you crazy. Fortunately toilet technology is uncomplicated and with just a little bit of knowledge you can obtain the know-how you need to fix that unwanted flow yourself.

Identifying the Problem

A bit of trial-and-error might be necessary to discover the real reason why your toilet keeps running. In most cases the source of the trouble can be traced to one of four possible causes, each of which—thankfully—can be fixed with relative ease. Here are the possible culprits: #1 Faulty flapper Problem: The flapper is the rubber stopper that pops open to let the water in the tank rush into the bowl after you flush. Once the flushing cycle is complete the flapper drops back into place so the tank can refill. But flappers can become cracked, worn or coated with mineral deposits. This prevents them from fitting tightly over the pipe that supplies the toilet bowl with water. As a consequence water will leak continuously from the tank into the bowl. Solution: To gain access to the interior of the tank turn the shut-off valve clockwise to cut the water supply, flush, and wait for the tank to empty. If the flapper is in rough shape remove it and replace it (a new one will cost about five bucks at the hardware store). #2 Excessive chain length Problem: The chain that lifts the flapper is too long and occasionally gets caught inside the lid of the flapper, preventing the latter from closing completely. If this is the trouble the constant running will tend to come and go. Solution: This foul-up will be easy to spot when you lift the top off the tank. To fix it, empty the tank and turn off the water so it can’t refill, and then unhook the chain by its ends and remove it. Use a wire cutter to snip off a few links (but not too many!) and re-install. #3 The float valve is set too high. Problem: The float valve is designed to shut off the water flow when the tank has refilled to an adequate level. But if it is set to the wrong level the water may continue to rise until it begins to empty into the overflow pipe, which in turn empties into the toilet bowl. The float valve can’t trigger a shut-off then because the water level in the tank can’t rise any higher. Solution: Your float valve will be either a large, round ball that bobs on top of the water (older toilets) or a floating black cylinder that fits over an assembly on the left side of the tank. In either case a screw will be provided to adjust for height, and you can use a flat screwdriver to drop the float down to a lower level. #4 The ballcock assembly needs to be replaced Problem: Something has gone wrong with the entire mechanism responsible for refilling your tank after it flushes. In this instance discovery occurs by process of elimination: if the other possibilities have been discounted this is most likely the source of the trouble. Solution: You can buy a new ballcock assembly at the hardware store and install it yourself. Instructions will be provided and it is not as difficult as you might think. If Nothing Else Works … If these DIY procedures all fail it’s safe to say you’ve got a real mystery on your hands, at which point calling a plumber may be your only realistic solution. Follow the Efficient Systems blog for oodles of heating, cooling, electrical and plumbing advice.