Boiler kettling: the banging and rumbling that means scale

What matters most with boiler kettling

• Hard water is a regional fact here, not a fault with your boiler
• Combi hot water plates scale before the main heat exchanger
• A magnetic filter catches iron oxide but not limescale
• Scale reducers protect new installs in hard-water postcodes
• Kettling that starts suddenly can also be a stuck pump

Understanding boiler kettling before you spend money

Bath, Wells and much of the Mendip belt sit on limestone, so mains water is hard. Scale forms on the hottest surfaces first — the domestic hot water plate exchanger on a combi, or the primary in an open-vented system. Chemical descaling can recover a mildly scaled exchanger; heavy scale usually means replacing the plate. Sludge-driven kettling is treated by flushing and fitting a magnetic filter.

What we see week to week with boiler kettling

We fit more scale protection in BA1, BA2 and BA5 than anywhere else on our patch, simply because of the geology. On a new combi in a hard-water postcode, in-line scale protection is a small line on the quote that measurably extends plate exchanger life.

Where we deal with this

• Bradford on Avon (BA15) · 9 mi
• Larkhall (BA1) · 9 mi
• South Stoke (BA2) · 8 mi
• Westfield (BA3) · 1 mi
• Mells (BA3) · 4 mi

Questions we get asked

Will a descaler cure kettling?

Sometimes. Light scale responds to chemical treatment; heavy scale usually needs the component replacing.

Is kettling dangerous?

It is not immediately dangerous but it stresses the heat exchanger and wastes gas or oil.