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Identify a Toilet Leak

DIY Questions and Answer November 20, 2015 Sonia



Q. My water bill has been on steady incline the last few months. The water department says I must have a plumbing fixture, but I don’t see any sign of one. Is there a way to look for unseen leaks?

A. A leaking faucet should be visibly evident, but toilets can have “silent” leaks. A dye test is a tried-and-true method for testing that plumbers have used for many years. To test, remove the tank lid and any colored cleaners that may be in the tank. Flush until the tank fills with clear water. You’ll need a dye capsule or some food coloring—even powdered Kool-aid will work. Apply enough dye to give the water a deep color tone. Leave the toilet unused and check the water in the bowl after 30 minutes to an hour. If dyed water is in the bowl, you have a leak. The next step is to determine if the leak is coming from the flush valve or fill valve. Make a pencil mark at the full water line inside the tank wall. Turn off the water supply and weight about a half hour. If the water stays at the level of the pencil mark, then the leak is at the fill valve. If the water level has fallen, the leak is occurring in the flush valve.