Water Heater Ticking Like a Clock
On this page (7 sections)
The Short Answer: A clock-like ticking near a water heater is usually harmless: hot-water pipes expanding as they warm and rubbing on straps or framing, heat-trap fittings on the tank connections, or a check valve in a recirculation line. The one ticking sound that needs attention right away is water dripping into the drain pan or onto metal, because that is a leak. Time the sound and look for water before deciding.
When does it tick?
The timing is the best clue:
| When you hear it | Likely source |
|---|---|
| For a few minutes after hot water is used, along the pipes, then it stops | Pipes expanding and contracting against straps, joists or drywall |
| At the top of the tank as water starts or stops flowing | Heat-trap nipples (small check balls or flaps in the tank connections) |
| All the time while a recirculation pump runs | Check valve in the recirculation line fluttering |
| Steady and regular, with a wet spot in the pan or on the floor | Water dripping from a fitting, the relief valve, or the drain valve |
| Clicks when a tankless starts or stops | Normal valve, relay or fan operation |
| Clicking from a gas tank’s burner area | Normal on some electronic igniters during lighting; repeated clicking with no flame means ignition is failing |
Pipe expansion
Copper pipe grows noticeably in length as it heats. Where it passes through tight holes in framing or is held by tight metal straps, it can creep and tick until it reaches temperature, then tick again as it cools. This is common after a new heater or new piping is installed. A plumber can loosen or replace straps, add plastic isolators, or enlarge tight holes. It does not mean the heater is failing.
Heat traps
Many tanks come with heat-trap fittings in the hot and cold connections to reduce heat loss through the pipes. Some contain a ball or flap that can click as flow starts and stops. If the noise bothers you, a plumber can replace them with non-noisy nipples.
Check valves and recirculation
A spring check valve in a recirculation line can chatter when the pump runs, especially if house water pressure is high. If the ticking stops when the recirculation pump is off, the check valve or pump is the source. A check valve that fails can also let hot water mix into cold lines, which shows up as lukewarm cold water at distant taps.
Rule out a leak first
Wipe the drain pan, the floor around the heater, the relief-valve discharge pipe and the drain valve with dry paper towels. Wait a few minutes and check again. A steady drip into a metal pan sounds a lot like a clock. If you find water:
- From the relief-valve pipe: see overflow keeps discharging
- From a connection or gasket: see water heater gasket leak
- From the tank itself: the heater needs replacing; see leaking from the bottom
What the plumber will check
They will listen to locate the sound, check house water pressure and the expansion tank (high pressure makes check valves and relief valves noisier), inspect straps and pipe supports, and look at heat traps and any recirculation check valve.
Frequently Asked Questions
Q: Is a ticking water heater dangerous? A: Expansion and heat-trap ticking are not. A drip that sounds like ticking is a leak that should be fixed. A gas heater that clicks repeatedly without lighting, or lights with a bang, should be turned off and serviced.
Q: Why did the ticking start after a new water heater was installed? A: New piping and straps are often tighter than the old ones, and many new tanks have heat-trap fittings. Both are common sources of ticking that are not defects.
Q: Will flushing the tank stop the ticking? A: Usually not. Flushing addresses sediment, which makes popping or rumbling sounds rather than a steady tick.
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 51: puddles around a heater (opens in a new tab)Common water-leak sources and the distinction between fittings and a failed tank.
- 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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