When low pressure shows up at every tap, the cause sits upstream of any single fixture — most often a partly closed main shutoff valve, a failing pressure regulator, a hidden leak, sediment in the pipes, or a problem with the municipal supply. Normal household pressure is generally 40–60 PSI; under 40 PSI is considered low.
First: is it the whole house or one fixture?
If only one faucet or showerhead is weak, the cause is local (usually a clogged aerator or cartridge). If hot and cold are both weak at every outlet, work through the whole-house causes below. If only hot water is weak, see our water heater guide instead.
Check the main shutoff valve
A main shutoff valve that is only partly open — for example after recent plumbing work — restricts flow to the entire house. Confirm it is fully open. If you need to locate it, our guide to shutting off your water shows where to look.
The pressure regulator
| Sign | What it suggests |
|---|---|
| Pressure drops suddenly or fluctuates through the day | Failing pressure-reducing valve (PRV) |
| Consistently low across every tap | Regulator set too low or failing |
| A bell-shaped valve near where the main enters the house | That is typically the regulator — adjustable on some models |
The pressure regulator (pressure-reducing valve) controls the pressure entering your plumbing. These typically last roughly 10 to 15 years, and a failing one can cause low or erratic pressure throughout the home. Testing and replacing it is a job for a plumber.
A hidden leak
A leak somewhere in the supply piping — under a slab, in a wall, or in the yard — diverts water before it reaches your fixtures. To test, close every tap and appliance, then check your water meter: if it keeps moving, water is going somewhere unseen. This is worth a prompt plumber visit.
Sediment and old pipes
In older homes with galvanized steel supply lines, internal corrosion and mineral buildup gradually narrow the pipes and reduce flow. Sediment can also collect in valves and fixtures. If pressure has declined slowly over years rather than suddenly, this is a likely cause and may eventually mean repiping.
A municipal supply issue
If your neighbors report weak pressure too, or it changes at predictable times of day, the cause may be the municipal supply or work on the main nearby. Contact your water utility before paying for plumbing diagnostics.
Measure your actual pressure
- Buy an inexpensive hose-bib pressure gauge
It threads onto an outdoor spigot or a laundry faucet connection.
- Close all water use in the house
So the reading reflects static pressure.
- Read the gauge
Roughly 40–60 PSI is normal; below about 40 PSI confirms a whole-house pressure problem rather than a fixture issue.
When to call a plumber
A failing pressure regulator, a suspected hidden leak, or corroded supply piping all need professional diagnosis. If you also have a softener or filters, see our water softener guide, since a clogged treatment system can restrict flow as well.
