Four Situations, Three of Them Benign
Evening only, fine again by morning — this is the well
If taps run clean in the morning, start spitting air by evening, and are fine again the next day, that is a yield signature. The well is being drawn down through the day faster than its fractures refill it, the water level reaches the pump, and the pump starts picking up air.
This is the pattern that matters most to recognise, because the instinctive response — a bigger pump — makes it decisively worse. See well ran dry for the actual options: storage, hydrofracking or deepening.
All the time, and getting worse — also the well, more urgently
Persistent and worsening air means the water level is sitting at or near the pump more or less permanently. That could be a declining yield, a well that has been over-drawn, or a pump set too high in the bore. Occasionally it is a leak in the drop pipe drawing air in on the suction side.
This needs attention rather than monitoring. A pump repeatedly drawing air is repeatedly running partly dry, and that shortens its life considerably. Reduce water use in the meantime and avoid long draws.
Just after work on the system — usually nothing
Air introduced during a repair or an installation, sitting in the lines and working its way out. Run the taps for several minutes each, starting with the lowest fixture in the house and working upward. It normally clears within a day or two.
If it persists beyond that, something is actively drawing air in rather than merely holding it — a fitting not sealed, or a check valve not seating. Go back to whoever did the work.
After the house stood empty — the seasonal classic
One of the most common calls we get in May, across Moultonborough, Tuftonboro, Center Harbor and every other seasonal shoreline. A system drained for winter and refilled holds air, and running it through clears it.
What to watch for is air that does not clear, because that points at something that happened over the winter: a fitting that let go in the cold, a check valve not seating, or a pressure tank that lost its charge while nobody was there.
The Other Explanations
- A waterlogged pressure tank — usually produces short-cycling too
- A jet pump losing prime — only applies to surface-mounted jet pumps, common on older shallow wells around the Suncooks and on some converted camps
- A failing check valve letting the column drain back between cycles
- Naturally occurring dissolved gas — rare, and it produces cloudy water that clears from the bottom up rather than violent sputtering
- Methane — genuinely rare in this region, but if water fizzes persistently and you can smell anything, stop and get it tested
That last one deserves a word. Persistent gas that you can smell is not a plumbing curiosity — get the water tested before doing anything else. It is very unlikely, and it is also the one possibility on this page worth ruling out properly rather than assuming.
Questions
Is the air itself harmful?
No. What it indicates can be. A pump repeatedly drawing air is repeatedly running partly dry, and that is what shortens its life. Treat persistent air as a symptom worth diagnosing rather than an inconvenience worth tolerating.
How do I bleed air out of the lines?
Open the lowest fixture in the house first and run it for several minutes, then work upward through the house one fixture at a time. That pushes air ahead of the water rather than trapping it. If it comes back after clearing, the system is drawing air in rather than merely holding it.
It only happens in late summer. Should I worry?
It means your well is marginal at peak demand in the driest part of the year. Whether that needs action depends on how far it goes: occasional evening sputtering in a dry August on a seasonal property is common and often tolerable. Sputtering that starts earlier each year, or begins happening in June, is a well that is declining and worth addressing before it forces the issue.
Can it damage my plumbing or appliances?
Air slugs can cause knocking and are unpleasant, but the more meaningful risk is to the pump rather than the plumbing. Dishwashers and washing machines cope with it reasonably well. The pump is the expensive thing in the equation.