Quick Answer:
If you hear air noise and see sputtering after backflow work or testing, it’s usually trapped air moving through the pipes. First check whether the sputter is worst at outdoor bibs or irrigation lines or if it’s happening throughout the house. Try running a cold faucet slowly to purge the air. If the backflow device is utility-owned or part of a required test assembly, don’t adjust it yourself — call the installer or the utility instead.
Why This Happens
Backflow devices and associated testing often require shutting and opening portions of the supply or filling sections of pipe. That can introduce pockets of air or shift air that was already in the system. Outdoor lines and irrigation are common spots because they have long runs and extra valves that trap air, but indoor fixtures can show the effect if air moves into the main lines.
Similar conditions occur after adjustments to pressure-reducing valves or when lines are refilled after seasonal work — think of short bursts of noise as air traveling down the plumbing. If the recent work involved winterization or refilling irrigation, this is the most likely cause. You may find it helpful to read about Air in pipes after PRV adjustment and Air pockets after winterization for similar scenarios.
Step-by-Step What to Do
1. Identify where the problem is worst
- Test a few fixtures: an outdoor hose bib, a bathroom cold tap, and a kitchen cold tap. Note whether sputtering is limited to outdoor/irrigation lines or present throughout the home.
- If only the outdoor fixtures or irrigation sputter, the issue is likely trapped air in those lines rather than the house plumbing.
2. Purge the air by running a cold faucet
- Open a cold water tap slowly at full bore and let it run for several minutes. Slow, steady flow helps push air out without creating pressure spikes.
- Start with the fixture nearest the meter or backflow device and work toward the farthest fixtures. For irrigation, run each zone briefly to clear air from the lateral lines.
3. Check hose bibs and irrigation valves
- Open outdoor valves and hose bibs one at a time to let trapped air escape. If you have a separate shutoff for irrigation, operate the zone valves to cycle and purge air.
4. Watch for leaks and persistent noise
- If you see continuous sputtering, whistling, or visible leaks, stop and reassess. Persistent noise can indicate a faulty valve, a stuck check, or a pressure issue that needs repair.
5. Don’t touch utility-owned or tested assemblies
- If the backflow device is owned by the water utility or is part of a mandated test assembly, do not attempt to adjust, loosen, or reconfigure it. Contact the installer or utility to report the issue.
What Not to Do
- Don’t adjust backflow devices yourself; improper changes can create safety and compliance issues.
- Don’t use hot water to try to clear air — use cold taps so you don’t risk scalding while you’re troubleshooting.
- Avoid opening multiple valves or turning assemblies without knowing their purpose; that can introduce contamination risks or change system pressures.
When to Call a Professional
- Call the installer or utility if the device is utility-owned or was installed/tested by a contractor — they are responsible for corrective work on that assembly.
- Call a licensed plumber if sputtering continues after purging, if multiple fixtures are affected for more than a few hours, or if you find a leak or a valve that won’t operate normally.
- If you notice discolored water, foul odor, or loss of pressure after purging, stop using the water and call a professional immediately.
Safety Notes
- Always use cold water when flushing air from lines to avoid scald risks.
- Do not tamper with backflow preventers that are marked as utility property or sealed after testing.
- If you must shut off the main water, know the shutoff location and how to operate it; if unsure, wait for a professional to avoid accidental contamination or pressure issues.
Common Homeowner Questions
- Why is my outdoor spigot sputtering after the test? Air trapped in outdoor runs or irrigation zones is common after service; run the zone briefly or the outdoor bib slowly to purge it.
- How long will the air noise last? Usually minutes to a few hours after purging; persistent noise beyond that suggests a leak, a stuck check valve, or other problem that needs a pro.
- Can I fix this by adjusting the backflow device? No. Don’t adjust backflow devices yourself — contact the installer or utility, especially if the assembly is part of a required test program.
Related Articles
If you’re troubleshooting a similar symptom, these guides may help:
For the full directory, see Air in Pipes After Shutoff.