If it's lime scale, try a 50/50 solution of white vinegar and water. Fill the tank with it, pump it through the faucet(s) and let it set in the lines for an hour or so. Then remove the aerator from the faucet(s) and run the solution through them for a couple minutes or so each. Next, remove the tank and drain it. Add about 1/4 cup of baking soda to it, and fill it full of water to get the vinegar taste/smell out of it. Hook it back up to the water system, fill the lines and faucets with this solution and let it set, again for about an hour. Finally, flush the tank, water lines & faucets several times with fresh water, and reattach the faucet aerator(s). That should take care of the problem, and the water should taste better, as well. Works well for cleaning the coffee maker and the steam iron, too. (But cut the baking soda to about a tablespoon for the coffee maker, and you won't need it at all in the steam iron.)