Quick Answer:
Short-term pressure drops that line up with storms are usually caused by changes to the supply side or by system components reacting to the event. Start by installing a pressure gauge with a peak (max) needle, log when lows happen, and isolate whether the issue is upstream (utility or meter) or inside your plumbing. Track irrigation schedules and PRV behavior while storms are happening to find a pattern.
Why This Happens
Storms can affect water pressure in several ways:
- Municipal supply pressure can dip with high demand, main breaks, or emergency flows during heavy rain.
- Air can enter lines during disturbance, causing temporary pressure swings and sputtering at fixtures.
- Pressure-reducing valves (PRVs) and pump controllers can cycle oddly when the supply changes rapidly, producing short drops.
- Irrigation systems or other large loads may run more or less during a storm window and change local pressure.
If you also see seasonal or weather-related losses, compare notes with **Pressure loss after freeze-thaw cycles**. If the timing is less clear on some days, consult **Intermittent pressure loss with no pattern** for other approaches to diagnosis.
Step-by-Step What to Do
1. Install a gauge with a max-needle
Buy a test pressure gauge that has a peak (max) needle or peak-hold feature. Attach it to an outdoor hose bib or the laundry sink drain cock so you can read supply pressure at the house connection. The max-needle records short dips you might miss with a standard dial.
2. Log and correlate events
- Record date, start and end time of any pressure drop captured by the max-needle.
- Note concurrent items: is your irrigation controller running, did the storm have heavy rain or lightning, and did the PRV cycle or pump run at that time?
- Compare your log to the storm timeline and to irrigation schedules—this will help separate weather-driven supply changes from scheduled loads.
3. Isolate upstream vs downstream causes
- Close the house shutoff or isolation valve and check pressure at a tap before the shutoff (if accessible) and after it. If pressure drops disappear when the house is isolated, the issue is inside; if they persist, the supply side is likely at fault.
- Temporarily turn off irrigation zones and any automatic loads during a test storm window to see if pressure holds. If turning irrigation off prevents the drop, that points to load-related pressure loss.
- If you have a well system, check the pump controller and pressure tank behavior during storms—look for rapid cycling or controller faults.
4. Monitor, document, and repeat
Keep a simple spreadsheet or notebook with timestamps, gauge readings, and what you turned off or on. Re-testing during similar weather is the only way to confirm a correlation and to determine whether the utility, PRV, pump, or a leak is the root cause.
What Not to Do
- Do not assume intermittent loss is a fixture issue—track system-wide behavior first.
- Don’t replace fixtures, faucets, or showerheads before confirming where the drop originates.
- Avoid attempting to remove or re-seal the water meter or utility seals yourself; that can violate local rules and be unsafe.
When to Call a Professional
- If the whole house loses pressure during storms and you cannot isolate whether it’s upstream or inside, contact your water utility first; they can confirm system-wide issues.
- Call a licensed plumber if you find pressure anomalies tied to your PRV, well pump, or internal piping and you’re not comfortable diagnosing further.
- Bring a pro if you document persistent drops, visible leaks, or repeated PRV/pump cycling—those can cause damage if left unresolved.
Safety Notes
- Do not work on outdoor plumbing during active storms—wait until conditions are safe and dry.
- Avoid contact with downed power lines or flooded areas near meters and electrical pump equipment.
- If you suspect the main has burst or there is a large leak, shut the house valve only if it is safe to reach; otherwise contact the utility.
Common Homeowner Questions
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Q: Why did my pressure drop only when it rained?
A: Likely a supply-side pressure dip, air in lines, or increased local demand during the storm; logging with a max-needle gauge will confirm.
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Q: Should I call the water company first or a plumber?
A: Call the water company first if the whole area or whole house is affected; call a plumber if the problem appears confined inside your property or involves PRV/pump equipment.
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Q: How long should I monitor before deciding it’s a utility issue?
A: Capture data over several similar storm events; if drops recur at the same time with the same pattern, it suggests a utility or external source.
Related Articles
If you’re troubleshooting a similar symptom, these guides may help:
For the full directory, see Intermittent Pressure Loss Events.