If you've noticed that a faucet in your house is running very slow, but it's only the hot water that seems to have the problem, there's a good chance you've got sediment built up in the hot-water line. It can happen in both lines, but it tends to be worse in hot-water lines. The heat more readily breaks up minerals from the sides of the pipes and sends them swishing around the system. There is a quick way to flush out that line by running cold water through it in reverse and giving it somewhere to expel the material. All it costs is a little wasted water and one dime.
Go to your water heater and turn off the cold-water supply that runs to the tank. This will generally be a valve located directly above the tank, or somewhere near it, on the cold-water line. You can tell which line is cold by touching it.
Go to the lowest faucet in the house that is not having the water-pressure problem, ideally a basement faucet. Turn the hot water on full and let it run.
Locate the faucet that's having the problem. Close the drain (so the rubber washer can't fall down it when you take the aerator off). Remove the aerator screen at the end of the faucet by turning it clockwise. Once it's off, make sure to keep holding it in the same upright position as it was on the faucet, so the washer doesn't fall out.
Press the dime into the aerator, flat side down against the screen, to completely close it off. Depending on the design, you may have to remove the washer, put the dime under it, and put the washer back in over it. In most faucets, the dime will fit perfectly. Now replace the aerator on the faucet, turning it counter-clockwise.
Slowly turn on the cold water tap until it's fully on, and leave it on. Water will not come out of the faucet (because the dime is blocking it), so the water will run back through the hot-water line.
Return to the faucet in step 2 and watch the water coming out; you will likely see discoloration and waste material in the water stream. Let it run for a few minutes, until the water runs clear again. Let it continue running while you go back to the faucet with the dime in it. Turn off the faucet, remove the dime, and replace the aerator. Then turn off the basement tap and turn back on the water line to the water heater.