There can be a number of causes for low pressure, but the most common problem is that there is no low pressure, only low flow. The symptoms may be the same, but the causes are different. Especially in older homes with galvanized iron pipes, the problem is rust on the inside of the pipe.
Over many years, the rust builds up and reduces the inside diameter of the pipe. What may have started out as an inside diameter of 3/4 inch may now be only 1/4 inch because of rust buildup. The pressure inside the pipe remains the same, but the volume of water is severely reduced. Unfortunately, the remedy for rust buildup in the galvanized pipes is to replace the pipe.
In newer homes, a sudden loss of water pressure usually means you have either a broken water line and very little water is getting through, or there is a pressure-reducing valve that is malfunctioning. Pressure-reducing valves eventually fail. When they do, one of two things will happen. Your pressure will drop to very little, or it will get very high. Neither is acceptable. The only solution is to replace the pressure-reducing valve.
By law, water districts are not allowed to work on a customer’s plumbing.
Homeowners may work on their own plumbing or hire a plumber. Check with counties to determine if a plumbing permit is needed for any work you do.