Quick Answer:
Small spurts of air after you refill a water heater are often trapped air in the tank or house pipes. Open a full faucet to purge the line and test whether the issue is only on hot or cold fixtures. If air keeps returning or shows up across multiple floors, have a plumber trace vents and supply components safely.
Why This Happens
- When a water heater is drained and refilled the tank and nearby pipes can trap pockets of air. That air will come out as sputters until it is flushed from the lines.
- One-way valves, check valves, or pressure-reducing devices on the supply side can hold air in sections of the plumbing, releasing it later at fixtures.
- Water main outages or partial refills after repairs can let air into the system. If the heater refill follows an outage, the timing matches trapped air being pushed through as pressure normalizes.
Step-by-Step What to Do
1. Identify where the spurting occurs
- Try a single fixture first. Note whether it happens with the hot tap, cold tap, or both.
- Test hot-only and cold-only by turning one side off at the faucet and running the other fully open for a minute.
- If it only happens on the cold side, check the bold note below for related guidance: Air only on cold water.
2. Purge the air by opening a faucet fully
- Open a nearby faucet all the way (preferably a bathtub or utility sink) and let it run until the sputtering stops and flow is steady. Opening fully helps push out trapped air faster than a trickle.
- Start with cold-only if you’re worried about hot-water scalding. After cold runs clear, repeat on hot water.
- If a single fixture clears but another still sputters, move to that fixture and purge it the same way.
3. Note timing and patterns
- Write down whether the spitting started right after a heater refill, after a power or water outage, or after you worked on valves.
- If the problem began immediately after shutting off or turning on supply, it’s useful to compare with the guidance on Sputtering faucet after shutoff.
- Check upstairs fixtures separately from downstairs—air can collect in high runs and behave differently on different floors.
4. Watch for recurrence and test across the house
- After purging, use fixtures on other floors and in different rooms. If air returns at several fixtures or on multiple floors, it likely isn’t an isolated faucet issue.
- If a single fixture continues to spit despite purging, the fixture cartridge or aerator may be involved—don’t dismantle cartridges unless you’re comfortable with reassembly.
What Not to Do
- Don’t keep cycling the main shutoff valve to the house trying to “blow” the air out; repeatedly opening and closing the main can introduce more air or stress plumbing components.
- Don’t dismantle cartridges, internal faucet parts, or appliances unless you know how to reassemble them and can shut off water safely.
- If air returns after purging or affects multiple floors, don’t try complex fixes yourself—let a plumber inspect venting, check valves, and supply components rather than guessing at internal parts.
When to Call a Professional
- Call a plumber if the air keeps coming back after you purge fixtures or if more than one floor is affected; a pro can safely trace the source and check valves, expansion devices, and heater venting.
- Also call if you notice pressure loss, continuous noise inside the water heater, or any leaks around the heater after a refill.
- If you’re unsure whether the heater was refilled correctly or a valve was left partially closed, a technician can verify tank fill, relief valve operation, and supply pressure.
Safety Notes
- Be careful of hot water when testing or purging. Run cold-only first if you’re unsure of water temperature.
- Do not attempt gas or electrical repairs on the water heater yourself. If the heater needs shutoff for diagnosis, a plumber or licensed technician should handle power or gas controls when required.
- If you smell gas, leave the house immediately and follow your local emergency instructions—do not try to diagnose or fix gas issues yourself.
Common Homeowner Questions
- Why did the air start after the heater was refilled? Trapped air in the tank or lines is the most common cause; it exits as the system refills and pressure equalizes.
- Is it safe to keep using water while it sputters? Generally yes, but use caution with hot water to avoid scalds. If sputtering is widespread or accompanied by pressure loss, stop and call a plumber.
- Will turning the main valve off and on fix it? No — repeatedly cycling the main can make the problem worse. Purge fixtures or call a pro if it persists.
For more related articles, see the Air Spitting From Faucets hub.