Quick Answer:
If water pressure drops without warning anywhere in the house, treat it as a system-wide issue and methodically test. Start by installing a pressure gauge with a max-needle, watch when drops happen, and try to isolate whether the problem is upstream (public supply or service line) or downstream (your plumbing, valves, PRV, or equipment).
Why This Happens
- Supply interruptions from the utility or bursts in the street can cause intermittent loss.
- Pressure-reducing valves (PRVs), well controls, or booster pumps can cycle or fail and cut pressure briefly.
- Automatic systems like irrigation, fire sprinklers, or water softeners can create sudden demand that looks like a cutout.
- Weather-related events (storms, freezing, or maintenance) may affect municipal pumping or valves.
- Hidden leaks or intermittent valve failures inside the house can mimic supply problems, but you should confirm system-wide behavior first.
Step-by-Step What to Do
1. Put a test gauge on the system
Install a pressure gauge with a max-needle (peak indicator) at an accessible point near the main shutoff or a hose bib. The max-needle records the highest pressure before a drop and makes it easier to compare events over time.
2. Record pressure and times
- Check the gauge at different times of day and after any pressure event.
- Note conditions when drops occur: weather, time, whether irrigation or appliances were running.
- Look for patterns — repeated drops at the same time suggest an automatic system trigger.
3. Correlate drops with likely triggers
Compare your notes to likely causes: irrigation cycles, sump or well pump cycles, municipal work during storms, and PRV adjustments. If the pressure falls when irrigation is on, the system demand is the likely cause. If it happens during heavy storms, utility issues are more likely.
4. Isolate upstream vs downstream
- Close the house main shutoff to isolate your internal plumbing. If the pressure at the street or at an external meter remains variable, the problem is upstream (utility or service line).
- If pressure stabilizes after isolating the house, open sections of your plumbing one at a time (irrigation, softener bypass, booster pump) to find the load or failing device.
- Check with neighbors—if they have the same intermittent loss, it is almost certainly upstream.
5. Inspect the PRV, well controls, and pump systems
- Look for visible leaks, cycling pumps, or a PRV that sounds like it is hunting (opening and closing repeatedly).
- For well systems: watch the pressure switch and tank pressure; rapid cycling or failure to maintain set pressure points to controls or tank problems.
- For homes with PRVs: note whether the PRV cycles before the drop; a failing PRV can cause intermittent outages.
6. Log findings and act
- Keep a simple log: date/time, gauge reading, what was on (irrigation, pump), and whether neighbors saw it.
- If you identify a device (irrigation, softener, pump) causing the drop, service or replace that component.
- If the issue is upstream, contact the water provider with your log and gauge readings.
What Not to Do
- Do not assume intermittent loss is a fixture issue—track system-wide behavior first.
- Do not randomly replace parts without testing; that wastes time and money.
- Do not start major repairs on the main service or electrical pump controls if you are not experienced; get a pro.
When to Call a Professional
- If you cannot isolate upstream vs downstream causes after the basic checks.
- If you find a failing PRV, well pump, or pressure tank and are unsure how to repair it safely.
- If pressure swings are severe enough to damage appliances or if you suspect a large hidden leak.
- If your gauge shows erratic spikes or drops that you can’t explain from usage patterns or neighborhood behavior.
Safety Notes
- Turn off the main water before working on fittings. Use proper tools and thread sealant on gauge fittings.
- Electric well pumps and booster pumps involve electricity—disconnect power before inspecting electrical components.
- If you smell gas or see signs of structural damage from a burst, evacuate and call emergency services first.
- Be cautious when working on pressurized systems; relieve pressure before disconnecting anything.
Common Homeowner Questions
- Why does the pressure cut out only sometimes? Short answer: intermittent demand or a cycling control (irrigation, pump, PRV) or upstream utility events are the usual causes.
- How will a test gauge help? A gauge with a max-needle records peak and lets you compare before-and-after readings to spot patterns.
- Should I contact the water company first? If neighbors are affected or your tests point upstream, contact the water provider with your recorded times and gauge readings.
If you want a quick read on related symptoms, see Water stops briefly then returns and Intermittent pressure after outages.
Related Articles
If you’re troubleshooting a similar symptom, these guides may help:
For the full directory, see Intermittent Pressure Loss Events.