Question 1

Why are my pipes banging?

Accepted Answer

A bang when a tap or appliance shuts off is water hammer — moving water stopped abruptly, sending a shockwave down the pipe. A rattle or knock while water runs is usually a pipe that isn't clipped properly, vibrating against a joist. Neither is harmless: over time water hammer loosens joints and fittings. The clue is when it happens. Bang at the moment something shuts off — most often a washing machine or dishwasher, because their solenoid valves close almost instantly — is water hammer. The water was moving, it stopped dead, and the energy went into the pipework. Knocking or rattling while the water is actually running is mechanical: a pipe with a missing or loose clip, or one passing through a joist notch with room to move. Sometimes it's fixed by getting to the pipe and clipping it properly, which is easy where the pipe is accessible and less easy where it isn't. Water hammer is treated at the cause: a shock arrestor near the offending appliance, checking the incoming pressure isn't excessive, and making sure the pipework is properly supported so it isn't free to move. It's worth doing rather than tolerating — the repeated shock works joints loose, and a joint that has been worked loose eventually leaks, usually where you can't see it. A separate noise worth distinguishing: banging or kettling from the boiler itself, rather than the pipes. Nationally the stock answer is limescale in the heat exchanger — but Macclesfield's water is soft, soft enough that scale barely forms, so that is usually the wrong answer here. In this town a kettling boiler is far more likely to be full of sludge: black iron oxide, the debris of corroding radiators, settling where it shouldn't. That's a system-cleanse or power-flush conversation, not a descaling one, and anyone reaching for the limescale explanation in Macclesfield probably isn't from Macclesfield.

Question 2

I can hear a banging noise coming from my pipework. What could it be?

Accepted Answer

A bang when a tap or appliance shuts off is water hammer — moving water stopped abruptly, sending a shockwave down the pipe. A rattle or knock while water runs is usually a pipe that isn't clipped properly, vibrating against a joist. Neither is harmless: over time water hammer loosens joints and fittings. The clue is when it happens. Bang at the moment something shuts off — most often a washing machine or dishwasher, because their solenoid valves close almost instantly — is water hammer. The water was moving, it stopped dead, and the energy went into the pipework. Knocking or rattling while the water is actually running is mechanical: a pipe with a missing or loose clip, or one passing through a joist notch with room to move. Sometimes it's fixed by getting to the pipe and clipping it properly, which is easy where the pipe is accessible and less easy where it isn't. Water hammer is treated at the cause: a shock arrestor near the offending appliance, checking the incoming pressure isn't excessive, and making sure the pipework is properly supported so it isn't free to move. It's worth doing rather than tolerating — the repeated shock works joints loose, and a joint that has been worked loose eventually leaks, usually where you can't see it. A separate noise worth distinguishing: banging or kettling from the boiler itself, rather than the pipes. Nationally the stock answer is limescale in the heat exchanger — but Macclesfield's water is soft, soft enough that scale barely forms, so that is usually the wrong answer here. In this town a kettling boiler is far more likely to be full of sludge: black iron oxide, the debris of corroding radiators, settling where it shouldn't. That's a system-cleanse or power-flush conversation, not a descaling one, and anyone reaching for the limescale explanation in Macclesfield probably isn't from Macclesfield.

Question 3

What is water hammer?

Accepted Answer

A bang when a tap or appliance shuts off is water hammer — moving water stopped abruptly, sending a shockwave down the pipe. A rattle or knock while water runs is usually a pipe that isn't clipped properly, vibrating against a joist. Neither is harmless: over time water hammer loosens joints and fittings. The clue is when it happens. Bang at the moment something shuts off — most often a washing machine or dishwasher, because their solenoid valves close almost instantly — is water hammer. The water was moving, it stopped dead, and the energy went into the pipework. Knocking or rattling while the water is actually running is mechanical: a pipe with a missing or loose clip, or one passing through a joist notch with room to move. Sometimes it's fixed by getting to the pipe and clipping it properly, which is easy where the pipe is accessible and less easy where it isn't. Water hammer is treated at the cause: a shock arrestor near the offending appliance, checking the incoming pressure isn't excessive, and making sure the pipework is properly supported so it isn't free to move. It's worth doing rather than tolerating — the repeated shock works joints loose, and a joint that has been worked loose eventually leaks, usually where you can't see it. A separate noise worth distinguishing: banging or kettling from the boiler itself, rather than the pipes. Nationally the stock answer is limescale in the heat exchanger — but Macclesfield's water is soft, soft enough that scale barely forms, so that is usually the wrong answer here. In this town a kettling boiler is far more likely to be full of sludge: black iron oxide, the debris of corroding radiators, settling where it shouldn't. That's a system-cleanse or power-flush conversation, not a descaling one, and anyone reaching for the limescale explanation in Macclesfield probably isn't from Macclesfield.

Why are my pipes banging?

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