The average toilet tank should fill within about three minutes depending on the water pressure in your area and in your home. If your toilet is taking too long to fill with water or isn't filling at all, you may have a partially closed shut-off valve or a clog in the fill valve tube. Troubleshoot the problem by checking one area at a time.
Check the water shut-off valve, which is located near the floor next to the toilet. You'll see a hose or tube connecting the valve to the toilet.
Turn the valve all the way to the left to ensure it is fully open. A previous owner, tenant or plumber may have left in a partially open position, or the valve may have been bumped partially or completely closed. Flush the toilet to test the fill speed. If the problem has not been fixed, move to the next step.
Turn off the water by turning the water shut-off valve all of the way to the right.
Clean the fill assembly inside the tank. Sediment may be lodged around the float cup or in the arm, preventing the assembly from moving properly. Using a clean rag, wipe any debris away from the float cup and arm and gently test that they can move freely up and down the fill tube. In an older toilet that has a ballcock assembly instead of the fill valve, unscrew the ball float and arm before wiping the ballcock assembly clean of debris. Reassemble after cleaning and turn on the water to test the toilet's fill speed. If cleaning the fill assembly has not solved the problem, move on to the next step.
Remove the valve top or cap. Depending on the type of fill valve you have, you may be able to remove the cap by pushing down and turning counter-clockwise or by gently prying it up with a screwdriver. Place a cup upside-down over the opening.
Turn the water back on while holding down the cup to clear debris from the fill valve and tube.
Turn the water off and reassemble the fill assembly.
Turn the water back on to test the fill rate. If cleaning the fill assembly has not solved your slow-fill problem, you may have a plumbing issue in the pipes in the wall.
Test the water pressure coming from your pipes to your toilet. Turn off the water. Disconnect the hose connecting the water shut-off valve to the toilet, at the toilet, and set the end of the hose in a bucket.
Turn the water on and check the water pressure. Low water pressure at this point is an indication of a larger plumbing problem that requires the attention of a professional plumber. Re-attach the hose to the toilet.
If your toilet is still filling slowly, and you do not suspect a plumbing problem, try replacing the fill valve completely.