Introduction
A pressure reading is only as good as the procedure behind it. This checklist turns pressure testing — the foundation of every diagnosis, estimate, and adjustment — into a repeatable sequence you can run the same way every time, whether it’s an annual checkup or the first step of troubleshooting a complaint.
Print it, run it with a gauge in hand, and feed the results into the Water Pressure Calculator to compare measured reality against calculated expectation. The estimating guide covers the measurement techniques each step relies on.
Before You Start: Preparation Checklist
- Gauge ready: hose-thread pressure gauge on hand; check that the dial reads zero with no pressure applied and that the threads are clean.
- Peak-demand timing: plan the test for morning peak use if you’re evaluating performance — municipal pressure is lowest when demand is highest.
- Know your system: locate the main shutoff, the PRV (if any), the water heater, and the expansion tank before you start. Note whether the system is closed (PRV or check valve present).
- Pen and paper: record every reading with its location, time, and conditions. Memory is not a measurement instrument.
- Household coordination: tell everyone in the house not to run water during the static readings — one flushing toilet invalidates the baseline.
The Core Test Sequence
- Static reading at the entry. Thread the gauge onto the hose bib closest to where water enters. Open the bib fully with nothing else running. Record the static pressure, location, and time.
- Verify the main valve. Confirm the main shutoff is fully open. If it’s a gate valve, exercise it gently — a valve that won’t fully open is itself a suspect (see the case study for what a half-open gate valve costs in PSI).
- Flowing reading at the entry. Without moving the gauge, have someone open a fixture inside (a tub or shower is ideal — high, steady flow). Record the flowing pressure and which fixture is running.
- Compute the entry drop. Static minus flowing at the entry is your system-level friction indicator: a few psi is healthy; 15+ psi means the service line, PRV, or main valve is restrictive.
- Branch readings. Move the gauge to a tap on the branch serving the complaint area (laundry tap, or adapt to a fixture). Repeat static and flowing readings. The branch drop isolates the problem’s location.
- Fixture isolation. If one fixture is the complaint, remove its aerator/showerhead and re-test. If pressure recovers, the fixture was the problem — done.
- Overnight spike check (if indicated). If you suspect thermal expansion or water hammer, leave a lazy-hand gauge on overnight or through a laundry cycle. Peak readings above 80 psi on a PRV-regulated system mean expansion or hammer, not supply pressure.
PRV Adjustment Checklist
- Gauge downstream. The gauge must be on the PRV’s downstream side. Adjusting without it is guesswork — one of the common mistakes.
- Record the starting pressure before touching the adjustment bolt.
- Loosen the locknut, then turn the bolt in quarter-turn increments: clockwise to raise, counterclockwise to lower.
- Run water briefly after each adjustment to let the valve settle, then read the gauge.
- Target 40–60 psi unless your situation dictates otherwise; never exceed 80 psi static.
- Tighten the locknut when done, and re-verify the reading — locknuts can shift the setting slightly.
- Confirm expansion control. Any PRV install or adjustment review should confirm the expansion tank exists and is charged correctly — PRV means closed system, closed system means expansion tank in most codes. Details in the code compliance guide.
Expansion Tank Verification Checklist
- Tap test: tap the tank — top should sound hollow (air), bottom solid (water). Fully solid means a failed diaphragm; replace the tank.
- Pre-charge check: with the water side depressurized, check the Schrader valve with a tire gauge. Pre-charge must equal house static pressure.
- Support check: the tank must be supported — a water-filled 2-gallon tank is heavy, and an unsupported tank stresses the fitting.
- Annual repeat: diaphragms lose air over time. Put the pre-charge check on the same annual schedule as the pressure test.
Interpreting Results: Decision Checklist
- Static 40–60 psi, small flowing drop, all fixtures fine: healthy system. Re-test annually.
- Static above 80 psi: PRV required by most codes — plan installation (pro job; see the DIY vs. pro guide) and add an expansion tank.
- Static fine, large flowing drop everywhere: supply-side restriction — main valve, PRV screen/failure, clogged filter or softener, or utility supply issue. Check the simple items, then call the utility before spending.
- Static fine, large flowing drop on one branch: branch restriction — valves, fittings, or pipe condition on that run. Work inward from the branch start.
- One fixture weak, system healthy: fixture-level fix — aerator, showerhead, angle stop, or supply line.
- Overnight spikes above 80 psi: thermal expansion (closed system) or water hammer — expansion tank verification or arrestors, per the material guide.
- Calculator predicts adequate pressure but gauge disagrees: the gap is the diagnosis — recheck fittings count, valve positions, and pipe condition; something unmeasured is throttling the run. The pro tips guide covers the isolate-and-compare sequence.
Related Guides
- Water Pressure Calculator FAQ — quick answers to the most asked questions.
- Estimating Guide — the measurement techniques behind each step.
- Pro Tips — testing and adjustment best practices.
- Common Mistakes — what goes wrong when steps are skipped.
- Cost Guide — what the fixes your checklist uncovers typically cost.
- Code Compliance — inspection-ready verification.
Get Your Number
Run the checklist, record the readings, and enter them into the Water Pressure Calculator alongside your elevation and pipe measurements. A completed checklist plus the calculator’s estimate is the complete pressure picture — and the document you hand a plumber if the fix turns out to be pro work. Make it an annual habit; pressure problems caught by routine testing are always cheaper than pressure problems caught by failure.
Disclaimer: Calculator results are planning estimates based on the dimensions you enter. Actual pressures depend on supply conditions, elevation, and system design. Verify against your local plumbing code and consult a licensed professional for pressure systems or potable water.
