Plumbing Guide
Why the water pressure dropped
By All Purpose Anytime Services LLC
Pressure problems often get diagnosed backwards. Two questions do most of the work. Is it every tap in the house or just one? And did it drop overnight, or fade a little each year until somebody noticed the shower?
One fixture, and it happened gradually
Almost always the aerator or the cartridge in that fixture. Mineral build-up closes the screen. It is a cheap fix and often not a plumbing visit at all.
Whole house, and it happened suddenly
Look at the main shutoff and the pressure reducing valve. A valve that has been knocked or has failed drops the whole house at once, and a valve at the end of its life does it without being touched.
Whole house, and it happened over years
This is usually the supply pipe itself. Galvanized lines corrode from the inside until the bore is a fraction of what it was, and no fitting change will bring the pressure back.
Replacing the affected run is the repair that works. Anyone offering to clean it out is selling you something that does not hold.
Pressure that is too high
Less common and more damaging. High pressure shortens the life of every fixture, valve and appliance in the house, and it is what makes supply lines let go. A gauge on an outside tap answers it in a minute.
Pressure questions from older houses
What does it mean when water pressure drops in one part of the house?
Usually a problem on the pipe that feeds that part. One fixture points to its aerator or cartridge. One bathroom or one floor points to the branch feeding it, often narrowed galvanized pipe, or a valve on that branch that is partly closed. With the rest of the house running normally, the meter and the main pressure reducing valve are ruled out.
Does low water pressure in an older home mean the pipes are failing?
Often, but check the cheaper causes first. Pressure that faded over years and is worst at the fixture farthest from the meter points to galvanized pipe closing up inside, and that run needs replacing. Pressure that dropped all at once points to the main valve or the pressure reducing valve. A gauge on an outside tap tells you which in a minute.
Pressure still weak everywhere?
Tell us whether it is one tap or the whole house, and how old the supply pipe is if you know. Whole house loss usually points at the line.