We often ignore the water pressure in our homes. It may go up and down, yet we seldom investigate the reasons behind the change in water pressure. We blame the water company, and leave it at that.
It may be the water company, but it could also be a sign of that your home has a water leak, or there is blockage in the pipes. If, this happens in your home more than once, you should contact your local plumber. Water pressure should under normal circumstances remain constant.