When most people ask for water pressure, they're really asking for water volume. It could be caused by a number of factors. The street pressure that's being provided to you might be low. You may be using a well that doesn't have much water. Maybe you have old pipes that are like clogged arteries. The way to increase volume is to install booster pumps, fix the well situation, or replace the pipe to get rid of the clogged arteries in the plumbing system.