Short definition
A pressure gauge is the homeowner’s primary diagnostic tool for water-supply problems. The most common form is a hose-thread test gauge that screws onto any exterior hose bib, reads 0–200 psi, and includes a telltale needle that records the maximum pressure observed since the last reset. A $10 part that answers most pressure questions in 30 seconds.
What it is
Two common forms in residential plumbing:
- Hose-bib test gauge. Three-quarter-inch female hose thread that screws onto any standard exterior hose bib. Portable, no tools needed. The standard homeowner diagnostic tool.
- Inline pipe-thread gauge. A permanent gauge tee’d into the supply, used on PRVs, well-pump systems, and some whole-house filters to give a continuous reading.
Most homeowner gauges have a 0–200 psi range, a normal needle, and a red telltale needle that the moving needle pushes upward and leaves at the highest reading observed. A small reset knob returns the telltale to the current pressure. Glycerin-filled gauges (the dial is liquid-filled) dampen needle vibration and last longer in systems with pulsation — worth the small price premium.
What the gauge reads is gauge pressure, the pressure relative to atmosphere. Absolute pressure adds about 14.7 psi at sea level for the atmospheric component, but in residential plumbing every code threshold and reference value is in gauge pressure, so the gauge reading is the number that matters.
Why it matters to a homeowner
The pressure gauge is the cheapest, fastest answer to a long list of plumbing complaints. Three high-value uses:
- Sudden low pressure. Connect, open the bib, read. Below 35 psi static is a real problem; investigate. Above 35 but below your historical normal points to a partial restriction worth following up.
- Suspected high pressure. Connect, open the bib, read. Above 80 psi static triggers the code requirement for a PRV. Many WA homes downhill of major hills routinely read 90–110+ psi.
- Nighttime pressure spikes. Leave the gauge attached overnight with the telltale set to the current reading. Read the telltale the next morning. Mains pressure peaks after midnight when neighborhood demand drops; a daytime reading of 75 psi can hide a 110 psi nighttime peak. The telltale captures it.
Most emergency-prep checklists for WA homeowners include “own a hose-bib pressure gauge” alongside the water-shutoff key and the gas-shutoff wrench. Cheap insurance.
Common variants and what gauges aren’t
- Test gauge vs. inline gauge. Test gauge is portable and screws onto any hose bib. Inline is permanent.
- Standard gauge vs. telltale gauge. Telltale records the max observed pressure between resets; the standard moving needle alone doesn’t.
- Liquid-filled vs. dry. Liquid-filled (glycerin) damps vibration and reads more steadily on systems with pulsation; dry is fine for static testing.