Quick Answer:
Small bursts of air before water flows usually mean trapped air in the supply lines after a shutoff, outage, or water heater refill. It can look alarming and make a homeowner worry the system is drawing air or losing pressure, but often you can clear it yourself. If the spitting repeats across multiple fixtures or floors, a plumber can safely trace the source and check venting or supply components.
Why This Happens
Air can enter or become trapped in the pipes for a few common reasons:
- Water main shutoffs, repairs, or brief outages allow pockets of air into the system.
- Refilling a water heater or plumbing after service can introduce air into the hot side of the system.
- Pressure changes or a failing check valve and venting problems can let air collect in certain runs of pipe.
- Elevation differences mean upstairs fixtures sometimes spit air while downstairs fixtures do not.
If it only happens on the hot side after the heater refills, the heater refill is the likely cause. If it shows up across many fixtures, it points to a supply or venting issue that needs tracing. A related household pattern is described in Sputtering faucet after shutoff and in cases limited to upper levels see Air only at upstairs faucets.
Step-by-Step What to Do
Open the faucet fully to purge air
- Fully open the affected faucet (all the way) rather than leaving it partially open. A full opening moves more water and clears air faster.
- Run it until the flow steadies and the sputtering stops—this can take a minute or several minutes depending on how much air is trapped.
- Collect the initial water in a bucket if you want to avoid splashing into sinks or fixtures.
Test hot-only vs cold-only
- Run only the cold side and note whether the spitting appears. Then run only the hot side.
- If the spitting is limited to hot taps, the water heater or its refill process is likely responsible.
- Use care when testing hot water—open it slowly at first to avoid scalding if the heater produces unexpectedly hot water.
Note timing: outages or heater refills
- Ask whether the spitting started right after a water outage, main shutoff, or when the heater was refilled. That timing is a strong clue.
- After those events, trapped air is common and often clears with simple purging.
Check upstairs vs downstairs
- Test the same fixture type on different floors (for example, a sink on the first floor and one upstairs). Differences can reveal pressure or venting patterns.
- If upstairs fixtures behave differently than downstairs, note which floors are affected and whether only cold or hot are involved.
- If multiple floors show the problem, don’t try complex repairs yourself—call a pro for a systematic inspection.
What Not to Do
- Don’t keep cycling the main valve in hopes the problem will go away; repeated rapid valve changes can damage seals and introduce more air.
- Don’t start dismantling cartridges, valves, or faucet internals unless you know the exact part and how to reassemble it.
- If air returns after purging or affects multiple floors, let a plumber inspect venting and supply components rather than attempting more invasive DIY fixes.
When to Call a Professional
- When air keeps coming back after you purge faucets, or the problem affects many fixtures or multiple floors.
- If you see sustained low pressure, noisy pipes when other fixtures run, or any sign of leaks during purging.
- After a water-main repair or complicated heater work, if you’re unsure whether the system was bled correctly.
- A plumber can safely trace vents, pressure regulators, check valves, and service the heater or main where needed.
Safety Notes
- Be careful when testing hot water to avoid scalding. Start with a small opening and increase flow once you know the temperature.
- Use a bucket or towel to catch sputtered water and protect finishes and electrical outlets nearby.
- If you smell anything unusual (strong chemicals, gas), stop and call the appropriate utility or emergency service; air in water lines is not related to gas lines, but unexpected odors need attention.
Common Homeowner Questions
- Why did this start after the water company shut off service?
Air entered the lines during the shutoff; purging your faucets usually clears it. - Is the house losing pressure if I see air first?
Not necessarily; trapped air causes sputtering but steady low pressure after purging suggests a pressure issue that needs checking. - Can I fix repeated spitting across floors myself?
If it returns after purging or affects many fixtures, call a plumber to trace vents, valves, and supply components.
For more related articles, see the Air Spitting From Faucets hub.