Quick Answer:
If water pressure drops or cuts out only during high simultaneous use (irrigation, many fixtures, or pump cycling), start by monitoring the system with a pressure gauge that records peak drops, correlate the timing with likely triggers, and isolate whether the problem is upstream (utility) or downstream (your house and property). Short tests and a log will usually show whether this is a capacity/supply issue, a control device (PRV/pump), or a local leak or valve problem.
Why This Happens
When many outlets run at once—sprinklers, washing machine, showers, and sometimes a well pump or PRV cycling—the total demand can exceed the supply capacity. That can make pressure fall quickly or cut out for a short time. Other common causes include temporary utility supply reductions, a failing pressure regulator, stuck pump controls, or blockages that limit flow.
Weather-related events or ground movement can cause intermittent reductions too; see Pressure loss after freeze-thaw cycles for how temperature cycles can create pinhole leaks and partial blockages. If the pressure drop lines up with your irrigation schedule, see Pressure loss when irrigation starts for steps focused on sprinkler-related demand.
Step-by-Step What to Do
1. Fit a pressure gauge with a max-needle
- Install a reliable gauge at the service entrance or at an accessible outdoor tap on the house side. Use a gauge with a max-needle or peak indicator so you can see the lowest and highest pressure over a short period without constant watching.
- If you have a PRV, put one gauge before the PRV (meter side) and one after it (house side) to compare readings.
- Note: Installing a gauge at the meter or on the utility side may require permission or a pro. Do the house-side gauge yourself on an exterior hose bib if you’re unsure.
2. Create a short log and correlate triggers
- Record time, pressure reading, and what was running (irrigation zones, showers, dishwasher, pump on/off, storms). Log for several events or a full day with typical heavy-use periods.
- Look for patterns: simultaneous pressure loss with irrigation start, during heavy rainstorms, or when the PRV cycles.
- Use the max-needle to capture brief collapses that you might miss in a spot check.
3. Isolate upstream vs downstream causes
- Compare meter-side vs house-side gauges:
- If both drop equally, the supply or utility side is likely the problem.
- If meter-side stays steady but house-side drops, the issue is on your property (PRV, service line, valves, or internal plumbing).
- Shut off the house main (inside shutoff) while the supply is under load:
- If pressure at the meter drops when your main is shut, the utility may be reducing supply.
- If meter pressure stays steady, your internal system or irrigation is causing the collapse.
- Test irrigation separately: run one zone at a time and watch the gauge. If a single zone causes the collapse, that zone may be oversized, have broken heads, or your supply isn’t sized for concurrent zones.
4. Check common on-property causes
- Inspect PRV operation and settings. PRVs that stick or are too low can collapse under demand. A pro can test and recalibrate or replace a failing PRV.
- Check pump control settings and the pressure tank (if you have a well). Rapid cycling or tank loss of air charge will drop pressure during use.
- Look for partial blockages or a closed valve on the service line or main feed to the house.
What Not to Do
- Do not assume intermittent loss is a fixture issue—track system-wide behavior first.
- Do not open or modify the utility meter or tamper with the utility-side equipment yourself.
- Do not replace parts (PRV, pump controls) without confirming the location of the issue through gauge comparisons and basic isolation tests.
When to Call a Professional
- If both meter-side and house-side pressure drop, contact your water utility—this is likely a supply problem.
- If testing shows the problem is on your property and you’re not comfortable with valve work, PRV replacement, or pump diagnostics, hire a licensed plumber or well contractor.
- Call a pro immediately for signs of a major leak (rapid pressure loss, visible water, or meter spinning with no known use).
Safety Notes
- Turn off electrical equipment before working near pumps or pressure controls.
- Use proper fittings and thread seal when installing gauges to avoid leaks. If you’re unsure about connections at the meter, stop and call the utility or a plumber.
- Avoid working on the utility side of the meter; utilities may require licensed personnel to access or modify that equipment.
Common Homeowner Questions
- Why does pressure return after a few minutes? Short drops that recover often point to a supply limit or cycling device (pump/PRV) that stabilizes after demand falls.
- Can I fix a PRV myself? You can often adjust a PRV, but replacement or complex diagnosis is best left to a plumber if you aren’t comfortable shutting water off and making the repair.
- How long should I log readings? Log during at least one full heavy-use period (morning or evening) and during an irrigation cycle; 24–48 hours gives the clearest pattern.
Related Articles
If you’re troubleshooting a similar symptom, these guides may help:
For the full directory, see Intermittent Pressure Loss Events.