Air in faucet after outage

Quick Answer:

After a power or water outage you may see air spit from a faucet as water and trapped air re-enter the pipes. Open the affected tap fully and let it run until the stream is steady; this usually clears the air. If spitting repeats across fixtures or on multiple floors, the system may need further diagnosis — a plumber can trace the source safely and check venting and supply components.

Why This Happens

• When the supply pressure drops during an outage, air can enter the plumbing. When pressure returns, that trapped air moves and causes spitting at the faucet.
• Water heaters and boiler refills often introduce pockets of air into the hot side when they refill after power loss.
• Upstairs fixtures are more likely to show spitting because air rises to high points in the system, or because of differences in pipe layout and pressure.
• Municipal system work, pressure surges, or a failing pressure regulator can also let air into the lines.

Step-by-Step What to Do

1. Open the faucet fully to purge air

• Turn the faucet handle to full open (both hot and cold if it’s a mixer) and let the water run. A steady stream means the air has been flushed out.
• Start with the lowest fixture in the house if multiple fixtures are affected, then move higher. This helps push air up and out.

2. Test hot-only and cold-only

• Run cold water alone, then hot water alone. If spitting happens only on the hot side, the water heater refill is the likely culprit.
• If only the cold side spits, the issue is in the supply line from the street or pressure equipment.

3. Note timing and patterns

• Pay attention to when the spitting occurs: immediately after an outage, after the heater refills, or only at certain times of day.
• Write down which fixtures are affected and whether the problem is intermittent or continuous.

4. Check upstairs vs downstairs behavior

• Run a fixture on a lower floor, then run one upstairs. If the problem appears only upstairs it suggests trapped air at high points or issues specific to that branch — for example, Air only at upstairs faucets.
• If one kitchen tap behaves differently from others in the house, note that too — for instance, Air from kitchen faucet only.

5. Repeat the purge if needed, but watch for patterns

• Occasional purging (opening taps fully) is safe and usually clears the problem. If air returns after purging, or the issue affects multiple floors, stop and seek professional help.

What Not to Do

• Don’t keep cycling the main shutoff valve to try to force the air out — that can introduce more air or disturb the pressure regulator.
• Don’t dismantle faucet cartridges, valves, or plumbing fixtures while the system is pressurized; that can cause leaks and damage.
• Don’t attempt complex repairs on the water heater or its pressure/expansion components unless you are a qualified technician.
• If air returns after purging or affects multiple floors, let a plumber inspect venting and supply components rather than attempting more aggressive DIY fixes.

When to Call a Professional

• If spitting continues after you purge the lines and happens repeatedly.
• If multiple fixtures or floors are affected, or if you see a sustained drop in water pressure.
• If you hear banging, tapping, or other noises in the pipes along with air spitting — these signs may indicate trapped air pockets or failing pressure-control devices.
• If you suspect the water heater is the source (persistent hot-side air, sputtering during refill) — a plumber can safely trace and repair heater-related issues.

Safety Notes

• Hot water can scald. When testing hot-only, open the tap slowly and be careful of steam or very hot water.
• Do not work on gas-fired water heaters or electrical elements unless you are qualified. Turning off gas or electricity should be done carefully and typically by a professional.
• Avoid using tools on pressurized pipes. Shut off water to the immediate fixture and relieve pressure before any disassembly.
• If water looks discolored or smells after an outage, avoid drinking it until it clears. Run the taps until water is clear and cold before using for drinking or cooking.

Common Homeowner Questions

• Why did this start after a power or water outage?
  Pressure drops let air into the system; when service resumes the air moves and causes spitting.
• Can I fix it by myself?
  Often you can clear it by opening and running the taps fully; if it returns or affects many fixtures, call a plumber.
• Is this a sign of a bigger problem?
  Occasional air after outages is normal; persistent air, pressure loss, or problems on multiple floors may indicate a plumbing or venting issue that needs professional diagnosis.

For more related articles, see the Air Spitting From Faucets hub.