5 Noises Your Unvented Cylinder Makes Before It Fails

Unvented cylinders usually operate pretty quietly. If yours has started making noises, it’s understandable to be a little concerned. Some noises are not much to be alarmed about, but some can be signs that your system is about to fail. Below are five common “panic noises”, what they usually mean, and when it’s time to call in a G3-qualified engineer.

The “Shudder” or Loud Bang After You Turn Off A Tap

This usually sounds like a thump, bang, or a brief vibration through the pipework when a tap, shower, or washing machine stops.

You may be familiar with the term “water hammer”, which is a pressure shockwave when the flow of water stops suddenly, or loose pipework moving against joists. Eco shower heads and some household appliances can make it more noticeable. Repeated hammering can stress joints and valves over time. Note when it happens (only hot? only certain taps?) and get the pipework secured and the cause assessed.

The “Whine”, “Whistle”, or Low “Foghorn”

This sounds like a high-pitched whistling when hot water runs, or a deeper foghorn-like moan. Usually, it’s water being forced through a restriction (partially closed valve, scaled shower head insert, blocked filter, etc.), or a pressure-reducing/control valve “chattering”. It usually means a component is working harder than it should, which means additional wear and tear and a shorter lifespan. Don’t ignore it if it’s new or getting louder. It usually means a diagnostic visit for an engineer.

Popping, Crackling, or Rumbling While Heating

This sounds like popping or crackling when the cylinder is heating (often during immersion use). The most common cause is limescale on the heating surface, essentially “kettling”. Hard-water areas are especially prone. Limescale is never a good thing, because it makes your system work harder, reduces cylinder volume, and shortens the unit’s lifespan. Book a service before it turns into a no-hot-water morning (or an immersion replacement).

Gurgling or a Trickle You Can See In The Tundish

Usually, this sounds like a faint trickle, but the key is that you can often see it through the tundish window. A tundish is designed to give a visible indication that water has been released from the system due to excessive pressure/temperature, and it should be in a safe, visible position so you can spot discharge.

Often, this means expansion vessel issues, a failing relief valve, or a pressure problem, and it’s a safety signal, so schedule a qualified inspection.

Rapid Clicking, Buzzing, or “On/Off Cycling” During Small Hot Draw-Offs

This sounds like repeated clicking or vibration when someone briefly uses hot water (hand wash, quick rinse). Often, this means there’s a control or mixing issue, sometimes linked to pressure imbalance, thermostatic valves hunting, or a component reacting badly to low-flow conditions.

Cycling means that your system is unstable. If you leave it for too long, it usually means that a component (or more than one) will wear out early. Have the system checked.

When to Stop Googling and Call Someone

If the noise is new, getting worse, or it’s paired with visible discharge at the tundish, that’s your cue to bring in a professional.

EasyFlow’s G3-qualified engineers can diagnose the cause and keep your system safe, and our annual service includes testing safety valves, recharging pressure vessels, cleaning the pressure reduction valve, checking electrics, and providing a service certificate. Contact us today to schedule your inspection.