Quick Answer:
Violent spray when you open a tap is usually a sudden pressure spike or a failed pressure regulator/backflow device. Stop using the affected fixture, shut its isolation valve if available, and follow the checks below: install a pressure gauge, isolate the PRV or backflow device, and monitor surge timing so you can describe the pattern to a plumber.
Why This Happens
Common causes include:
- Pressure regulator (PRV) failure or a stuck check valve that lets pressure spike when a tap opens.
- Transient spikes from the water main or a utility crew closing or opening a main line. A typical clue is a one-off spike at the same time mains are worked on — a Pressure surge after water main turn-on is a common pattern.
- Thermal expansion in closed systems (less common) or trapped air pockets that release suddenly.
- Faulty or clogged faucet cartridges and spray heads can change flow patterns and make spray worse when pressure varies.
Step-by-Step What to Do
1. Stop use and isolate the fixture
- Turn the tap off. If the spray is extreme, close the fixture’s isolation valve or the house shutoff to prevent damage.
- Turn off nearby electrical devices to avoid water contact with powered equipment.
2. Install a gauge
- Attach a simple pressure gauge to an outside hose bib, the washing machine supply, or other threaded service valve. A gauge gives numbers you can record.
- Record the static pressure with everything off, then open the problem tap slowly and watch the reading under flow.
3. Isolate PRV and backflow
- If your home has a pressure reducing valve or a backflow preventer, close the appropriate isolation valves to see whether the surge stops upstream or downstream of those devices.
- Do not disassemble the PRV or backflow device yourself unless you know how; isolation and observation are the safe first steps.
4. Monitor surge timing
- Note exactly when the spray happens — time of day, after nearby fixtures are used, or after the city works on mains. Keep a short log for at least a day.
- If the gauge spikes erratically while you open the tap, that indicates pressure transients; if the gauge is steady then the problem may be at the fixture.
- If the gauge reading jumps when you open the tap, that pattern — a Pressure gauge shows sudden jumps — helps a plumber diagnose the cause.
5. Try a cautious test
- Open the tap slowly, not fully, and watch whether the spray is controlled. Slow opening can reduce the immediate burst and avoid appliance damage while you assess.
- Do a quick test with another fixture to see if the problem is isolated to one tap or affects the whole house.
6. Record findings and prepare to act
- Keep the gauge readings, times of surges, and which fixtures are affected. This information speeds a professional diagnosis.
What Not to Do
- Do not ignore surges—they cause fixture and appliance failure.
- Do not remove or take apart a PRV or backflow device if you are not trained. That can make the problem worse or create contamination risks.
- Do not run washing machines, dishwashers, or water heaters when you suspect pressure spikes — appliances can be damaged by sudden overpressure.
When to Call a Professional
- Call a licensed plumber if the gauge shows consistently high pressure, sudden repeated spikes, or if you can’t isolate the issue.
- Also call if you see water damage, leaking fittings, or if spray is strong enough to be hazardous inside the home.
- If the PRV or backflow device appears to be the source, a professional should test, adjust, or replace those components.
Safety Notes
- Avoid standing water near electrical outlets and appliances. Turn off power to areas exposed to spray if needed.
- Use only basic isolation and observation steps unless you are experienced. Complex valve adjustments can introduce contamination or flooding risk.
- If you shut off the main water, remember to open a tap slowly when turning it back on to relieve trapped air and avoid sudden pressure changes.
Common Homeowner Questions
- Why does it only happen sometimes? Often it’s a pressure transient tied to specific events (main work, sprinkler cycles) rather than a constant failure.
- Can I fix this myself? You can do basic checks: install a gauge, isolate valves, and log timing. Major PRV or backflow repairs are best left to pros.
- Will this damage appliances? Yes. Repeated pressure spikes shorten the life of fixtures and appliances and can cause sudden leaks or failures.
Related Articles
If you’re troubleshooting a similar symptom, these guides may help:
For the full directory, see Pressure Spikes & Sudden Surges.