Water Heater Making a Gurgling Noise: Causes
On this page (6 sections)
The Short Answer: Gurgling is the sound of water and air or steam moving together. Right after the tank has been drained or the water was shut off, it is usually air working its way out and fades within a day. Ongoing gurgling while the heater runs is often sediment. Gurgling from the relief-valve pipe means water is being released, and gurgling in a condensate line points to a drain or trap issue.
Narrow it down by where and when
| Where and when you hear it | Likely cause | What to do |
|---|---|---|
| Faucets sputter and the heater gurgles after a flush, repair, or water shutoff | Air in the tank and pipes | Run hot taps until the flow is steady; it should settle |
| Gurgling or percolating from inside the tank while it heats | Sediment on the bottom (gas) or lower element (electric) | Schedule flushing or service; see water heater sounds like rocks |
| Gurgling or dripping from the relief-valve discharge pipe | Relief valve releasing water from high pressure or temperature | Prompt service; never cap the valve |
| Gurgling in a small plastic tube or pump near a heat-pump or condensing heater | Condensate draining through a trap or pump | Check that the drain is clear and the pump runs |
| Gurgling plus water on the floor | A leak, possibly from the tank | See water leaking from the bottom of the tank |
Air after draining or a shutoff
When a tank is drained, flushed, or the water main is shut off and reopened, air gets trapped in the top of the tank and the hot piping. As you use hot water, that air is pushed out with spitting faucets and gurgling at the heater. Opening a hot-water faucet and letting it run until the stream is smooth usually clears it.
On an electric heater, the tank must be completely full before the breaker is turned back on. Powering an element that is not covered by water burns it out within moments. A faucet running a smooth stream with no air is a good sign the tank is full; see water heater turned on without water if that step was missed.
Gurgling at the relief valve
The temperature and pressure (T&P) relief valve should stay closed in normal use. Gurgling at the valve or its discharge pipe means it is opening, usually from pressure building as the tank heats in a closed plumbing system, or occasionally from overheating. A. O. Smith’s thermal-expansion bulletin (opens in a new tab) explains that pressure rise. If the valve runs continuously or the water at your taps is unusually hot, turn the heater off and call for service. Why the relief valve keeps discharging has more on this.
Condensate gurgles
Heat-pump water heaters and condensing gas heaters produce condensate, which drains through a tube, sometimes via a trap or small pump. Some gurgling as water passes through is normal. Loud, constant gurgling, water backing up, or a pump that runs without emptying suggests a blocked line or trap. If your manual describes clearing the external condensate line as owner maintenance, follow it; otherwise have it serviced.
What the technician will check
They will listen to locate the source, check house water pressure and the expansion tank, test whether the relief valve reseats, flush sediment if the tank is in good enough condition, and clear or re-slope condensate lines. On an older tank with heavy sediment, they may advise that flushing is unlikely to help.
Frequently Asked Questions
Q: How long should gurgling last after I drained the tank? A: Usually only until the trapped air has been pushed out, often within a few uses of hot water or a day. If it continues for days with smooth flow at the taps, the cause is probably something else, such as sediment.
Q: Is gurgling a sign the tank is about to fail? A: Not by itself. Sediment noise often means the tank is older and has been running with mineral buildup, but failure is shown by leaks or rusty water, not by noise alone.
Manuals and supporting references
These links distinguish general safety information from model-specific documentation. A manual directory helps you locate your unit’s instructions; it does not establish that every model uses the same parts, codes, or test values.
- A. O. Smith technical bulletin 45: thermal expansion (opens in a new tab)Background on pressure rise in a closed water system. Pressure testing and repairs are professional work.
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