Symptoms
- Sound occurs specifically as cold water refills after hot water is drawn
- Noise is brief, lasting only while water is actively filling
- May sound like gurgling, hissing, or light clanking
- Not present during other parts of the heating cycle
Likely causes
- CommonNormal water flow and minor air movement in the pipeSome sound during refill is expected and not a sign of a problem.
- CommonSediment being disturbed as fresh water enters the tankIncoming cold water can stir sediment at the bottom, causing extra sound.
- PossibleWorn dip tube causing turbulent water flow inside the tankThe dip tube directs incoming cold water to the bottom; if it's cracked or degraded, water can splash and cause noise higher up.
- PossiblePartially closed or faulty inlet valve restricting flow unevenlyA valve not fully open can cause turbulent, noisy flow.
What to do
- Listen closely to characterize the noise: a brief, mild sound during refill is usually normal.
- If the noise is loud, harsh, or has grown more noticeable over time, flush the tank to remove sediment.
- Confirm the cold water inlet valve to the tank is fully open, not just partially.
- If sediment removal doesn't quiet it and the tank is several years old, a cracked dip tube could be contributing to the noise.
- A cracked dip tube often also shows up as lukewarm water despite everything else working normally.
- If you suspect the dip tube, a plumber can inspect and replace it, since it requires draining and partially disassembling the top of the tank.
Tools and parts
- Garden hose (for flushing)
Water heater dip tubeSearch: “water heater dip tube replacement”
When to call a pro
If noise persists after flushing and confirming the inlet valve is fully open, a plumber can check for a failing dip tube or valve.
Safety
Generally low risk
Generally low risk for a careful person. Stop if anything looks different from what this guide describes.