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Turn the water shut-off valve counter-clockwise to turn the water supply back on. Allow the tank to fill completely with water. Once the fill valve stops, listen to ensure the toilet is no longer running. Perform a test flush by pressing the handle. Observe the flapper to make sure it lifts high enough for a full flush and then settles back down to create a firm seal. If the flush is too short or long, you may need to adjust the settings on the flapper itself, if available.