Quick Answer:
After de-winterizing, some branches will trap air and sputter every time you open a tap. Start by listing which zones or branches were winterized and which fixtures are the highest in each branch. Purge air by opening the lowest cold fixtures first and work upward, one branch at a time. If a branch never stabilizes or any valve feels stuck or starts to leak, stop and call a professional.
Why This Happens
When a system is winterized it’s often drained, isolated with valves, or treated with compressed air or antifreeze. Air naturally collects at high points and in loops or isolated sections. Common causes:
- High fixtures or attic runs trap air at the top of a branch.
- A zone valve, shutoff, or mixing valve left partially closed isolates a pocket of air.
- Recirculation loops or alternate routing create a closed loop where air can’t escape.
If you see a pattern like Air in upstairs fixtures only, that tells you the trapped air is collecting at the highest runs and you should focus on high points and any one-way valves in that area.
Step-by-Step What to Do
1. Record which zones/branches were winterized and which fixtures are highest
- Write down each zone or branch you winterized (basement, main floor, upstairs, outdoor hose bibs, irrigation).
- Mark the highest fixture(s) on each branch (attic sink, upstairs tub, remote shower heads).
- Note any valves you closed during winterization (main shutoff, zone valves, individual fixture shutoffs).
2. Start purging at the lowest cold fixtures
- Turn on the lowest cold-water faucet for that branch (basement or lowest floor) and leave it open.
- Open the next-lowest cold fixture and let water run until sputtering stops and the flow is steady.
- Continue moving upward through the fixtures on that branch until the highest fixtures run clear and steady.
3. Watch for branches that never stabilize
- If a branch keeps sputtering or won’t hold steady after purging, check that its zone valve or shutoff is fully open.
- A persistent problem may suggest trapped air in a loop or a valve left closed; do not force anything that feels stuck.
- Isolate that branch and re-check all nearby valves and any recirculation pump settings before attempting more purging.
4. Re-check hot-water and recirculation lines
- After cold lines are stable, run hot taps to purge air from hot lines and the water heater bypass.
- If you have a recirculation loop, run the pump briefly and purge at the lowest point in that loop, then at high points.
5. Monitor for leaks and re-test
- After purging, close fixtures and watch fittings, valves, and exposed pipes for several minutes to catch slow leaks.
- If a branch repeatedly loses pressure or traps air again, it could be a stubborn loop or a valve issue such as those seen with Air pockets after replacing shutoff valves.
What Not to Do
- Don’t force winterization valves or compressor fittings if anything feels stuck—stop and call a professional.
- Do not apply high-pressure compressed air to domestic plumbing unless you are trained and the system is rated for it.
- Avoid repeatedly opening and slamming valves; gentle, controlled operation is safer and reduces risk of damage.
When to Call a Professional
- If any valve feels stuck, is hard to turn, or shows signs of damage.
- If you find active leaks, wet insulation, or water where it shouldn’t be during or after purging.
- If a branch keeps trapping air after you’ve purged and checked valve positions, or if you suspect trapped air in a loop or bypass you can’t access safely.
Safety Notes
- Shut off electrical power to circulation pumps before working on the system.
- Wear eye protection when opening fittings or working near pressurized lines.
- If antifreeze was used during winterization, flush lines thoroughly until water runs clear before using drinking water fixtures; collect and dispose of antifreeze according to local regulations.
- If you are unsure about any step, especially involving valves, pumps, or compressed-air equipment, call a licensed plumber.
Common Homeowner Questions
- Why do I get sputtering every time I open a tap? — Air is trapped at a high point or in an isolated branch; purge from the lowest fixture upward.
- Can I use a compressor to blow the air out? — Not unless you are experienced and the system is rated and prepared for compressed air; this can damage plumbing if done incorrectly.
- How long should purging take? — Typically a few minutes per branch; if steady flow doesn’t arrive after multiple attempts, get a professional to inspect valves and loops.
Related Articles
If you’re troubleshooting a similar symptom, these guides may help:
For the full directory, see Air in Pipes After Shutoff.