Quick Answer:
If only upstairs faucets or showers sputter and downstairs fixtures run clean, air is likely trapped in the upper branch of the plumbing. Verify the pattern by running an upstairs faucet slowly with the aerator on, then briefly running a downstairs cold faucet. If the upstairs clears only when the downstairs runs, the air is collecting in that higher branch and may need either simple flushing or a professional check for venting or crossover problems.
Why This Happens
Air can enter and become trapped in higher branches of a home’s water piping for a few common reasons:
- Recent work on the system (repairs, replacing fixtures, or shutting off a section) let air into the lines and it rose into the upstairs branch.
- A partial blockage, a dip in the pipe, or a vertical run that traps air can keep bubbles in the upper circuit while lower pipes stay full.
- Pressure differences between branches or a venting/crossover problem can move air into one area and not another.
Related, localized symptoms include sputtering from a shower head or appliance supply line—similar problems are described in Air coming from showerhead and Air in washing machine supply lines.
Step-by-Step What to Do
1. Confirm the pattern
Check multiple fixtures upstairs and downstairs to be sure the problem is limited to the upper floor. Note whether it affects cold, hot, or both supplies.
2. Prepare one upstairs faucet
Remove or check the aerator and run the upstairs faucet slowly on a steady stream with the aerator in place (or temporarily reinstalled). Running slowly helps bubbles move out without causing large pressure swings.
3. Run a downstairs cold faucet briefly
While the upstairs faucet is running slowly, quickly open a downstairs cold faucet for a few seconds and then close it. If the upstairs clears only when the downstairs runs, that indicates air is being drawn out of the upper branch when lower pressure changes—consistent with trapped air in the higher piping.
4. Observe behavior and pressure
If sputtering stops and normal flow returns after the brief downstairs run, you’ve likely flushed the trapped air. If the sputter persists or you see pressure swings (rapid changes in flow or banging), that suggests a more complex issue like venting, crossover, or blockage.
5. Repeat and document
Repeat the test on any other affected upstairs fixtures to confirm the pattern. Note how long the symptom returns after clearing and whether it’s only cold or hot—this information helps a plumber diagnose the root cause.
6. Next steps if it returns
If the problem returns quickly or pressure swings continue, stop further DIY attempts and consider a professional evaluation; persistent symptoms can indicate venting or cross-connection problems that need tools and experience to fix safely.
What Not to Do
- Don’t ignore that it’s upstairs-only. Treating it like a whole-house problem wastes time and can mask the real issue—confirm the location and pattern first.
- Don’t repeatedly crank water pressure to “blast” the lines; that can stress fittings and aggravate leaks or banging.
- Don’t assume it’s always the water heater or an appliance without checking fixture-by-fixture; narrowing the pattern prevents unnecessary replacement.
When to Call a Professional
Call a plumber if you see any of the following:
- Sputtering continues after you run the upstairs slow-aerator test and the brief downstairs cold-faucet test.
- There are frequent pressure swings, banging, or strange noises that suggest venting or crossover issues.
- The symptom returns quickly after temporary clearing, or you find multiple upstairs fixtures affected.
A plumber can test for trapped-air locations, check for partial blockages or improper venting, and investigate any cross-connections between hot and cold lines.
Safety Notes
- Work calmly and avoid creating sudden high pressure in the system.
- If you suspect a leak or see water where it shouldn’t be, shut off the affected supply and call a plumber.
- Don’t attempt major repairs to pressurized piping if you lack proper tools or experience—hire a licensed pro.
Common Homeowner Questions
- Why does air only affect upstairs fixtures? — Air rises and can collect in upper branches or vertical runs; downstairs lines may remain full so they don’t sputter.
- Will trapped air damage plumbing? — Short bursts of air usually won’t, but ongoing pressure swings or banging can stress fittings and should be checked.
- Can I clear it myself? — Yes for simple cases: run an upstairs faucet slowly with the aerator on, then briefly run a downstairs cold faucet to help pull air out. If it keeps returning, call a professional.
Related Articles
If you’re troubleshooting a similar symptom, these guides may help:
For the full directory, see Air in Pipes After Shutoff.