The two numbers
- Static pressure
- Pressure in the pipes with no water flowing anywhere. It reflects the supply and the regulator setting.
- Working pressure
- Pressure while water is flowing. It is always lower than static because moving water loses pressure to friction.
- Pressure drop
- The difference between static and working. A large drop points to restriction in valves, pipes or the regulator.
- psi
- Pounds per square inch, the unit on most household pressure gauges.
Taking both readings
- Get a gauge.A screw-on gauge that fits a garden hose thread, ideally one with a needle that marks the highest reading.
- Choose the spigot.Use a hose bib on the house side of the regulator, close to it.
- Static reading.With all water off, open the hose bib fully and note the number.
- Working reading.Keep the gauge on, open a bathtub tap and a kitchen faucet, and note the new number.
- Repeat at different times.Early morning and evening readings show daily swings in supply.
Reading the results
| Static | Working | What it suggests |
|---|---|---|
| High (over 80 psi) | Still high | Regulator missing, failing or set too high |
| Normal | Drops sharply | Restriction: partly closed valve, clogged regulator strainer or choked pipe |
| Normal | Modest drop | Supply and main line are probably fine; look at individual fixtures |
| Low | Lower | Supply side: regulator set low or stuck, main valve, line or street |
| Normal by day, high by morning | Varies | Thermal expansion or a regulator leaking through |
An illustrative example
Illustrative example. Not a real job or customer.
A two-story home near the top of a rise has weak upstairs showers. The homeowner reads a normal static pressure at the front hose bib, but it falls steeply when the tub and kitchen run together.
- The large drop suggests a restriction rather than a supply problem.
- The main shutoff turns out to be fully open, so the plumber checks the regulator's strainer and the pipe material.
- A section of old galvanized pipe near the water heater is found to be heavily narrowed inside.
Replacing that section restores flow upstairs without changing the regulator setting. This is an illustrative example, not a record of a real job.
Limits of a home gauge
A hose-bib gauge is a screening tool. It cannot show which pipe is restricted or whether a regulator's internal parts are worn. It does, however, tell you which direction to look and gives you a concrete number to share. Bring your log to a licensed plumber, and check their CSLB license at cslb.ca.gov before booking.
Common questions
Why is my working pressure always lower?
Moving water loses pressure through pipes and fittings. Some drop is normal; a very large drop is the clue to look for.
Where should I not take a reading?
Avoid hose bibs that are on the street side of the regulator or on a separate irrigation line, since they will not reflect house pressure.
Do gauges need to be accurate?
Inexpensive gauges are fine for screening. Readings that sit near an important threshold are worth confirming with the plumber's gauge.
General information for Coyote Hills, not a quote or professional advice. In an emergency, call 911.