One weak showerhead is usually a clogged nozzle. But when every faucet, every shower, and every hose bib in the house runs low at the same time, the cause is bigger than any one fixture — and no amount of cleaning a showerhead is going to fix it.
Here are the real causes of whole-house low pressure, roughly in order of how often we find them.
A partially closed valve
The simplest cause, and worth ruling out first: your main shutoff valve or the valve at the water meter isn’t fully open. This can happen after any plumbing work — including work by someone other than the original installer — if a valve was closed and not fully reopened. Check both before assuming something is broken.
A failing pressure regulator
Most homes have a pressure-reducing valve (PRV) where the main line enters the house, keeping city water pressure at a safe level for your plumbing. PRVs typically last 10 to 15 years. When one starts to fail, you’ll often see either consistently low pressure throughout the house, or pressure that swings unpredictably between fixtures and times of day. A failing PRV is a common, fixable cause of a whole-house pressure drop.
Corroded or scale-clogged pipes
Older galvanized steel pipes corrode from the inside over time, narrowing the passage water flows through. In San Jacinto’s hard water, mineral scale adds to the problem, gradually restricting pipes that were once wide open. This kind of pressure loss tends to develop slowly, over years, rather than appearing overnight.
Learn about whole-home repiping →A hidden leak
A leak — especially a slab leak — diverts water before it ever reaches your fixtures, which can show up as a sudden, unexplained drop in pressure throughout the house. If low pressure appeared suddenly rather than gradually, and especially if it’s paired with a higher water bill or damp flooring, a hidden leak is worth ruling out.
See our leak detection service →High demand on the municipal supply
Occasionally the cause isn’t your plumbing at all — heavy simultaneous usage in your neighborhood, or municipal system maintenance, can temporarily reduce supply pressure. This is usually short-lived and affects more than one household at a time.
What normal pressure looks like
Residential water pressure below 40 PSI is considered low; most homes run comfortably between 45 and 60 PSI. A plumber can check your actual pressure at the hose bib in a few minutes — a useful first step before diagnosing further, since it tells us whether we’re dealing with a true system-wide problem or something more isolated.
How we diagnose it
We start by testing pressure at the source and checking the regulator, then work through the possibilities above in order — valves, regulator, pipe condition, and leak detection if needed. Because a sudden pressure drop can point to something as serious as a hidden leak, it’s worth having a professional diagnosis rather than guessing.
Frequently Asked Questions
Why is my water pressure low in every faucet at once?
Whole-house low pressure usually points to a partially closed main valve, a failing pressure regulator, corroded or scale-clogged pipes, or a hidden leak diverting water before it reaches your fixtures. A single weak fixture is usually a local clog; all of them at once is a system-wide cause.
What is a normal water pressure for a house?
Most homes run comfortably between 45 and 60 PSI. Below 40 PSI is generally considered low. A plumber can measure your actual pressure at a hose bib in a few minutes.
Can a hidden leak cause low water pressure?
Yes. A leak — including a slab leak — diverts water before it reaches your fixtures, which can cause a sudden, unexplained drop in pressure throughout the house, often along with a higher water bill.