spots (white crystal like substance). if you notice this, make sure to have them replaced. if there is a bathroom that seldom gets used make sure to run all the fixtures. this includes sinks, shower/tubs, and toilets for several minutes to make sure there are no leaks. turn the angle stops on/off to make sure that they will still turn and function properly.
if your gas and/or electric water heater is 10 years or older and makes a popping noise like rocks are in it, it might be a good idea to have it replaced. in the winter time we use hot water more than in the summer. a water heater 