Acid descaling.

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What is acid descaling?

Acid descaling is a targeted cleaning process used to remove limescale, corrosion deposits, and other mineral build-up from hot water systems, calorifiers, and associated pipework. Over time, hard water can cause scale to accumulate on heat exchange surfaces, reducing efficiency, restricting flow, and creating ideal conditions for bacterial growth, including Legionella.

At Complii, we deliver bespoke acid descaling services to restore system performance and ensure compliance with HSG274 Part 2 and other UK water safety standards. Our engineers use controlled chemical descaling methods designed to safely dissolve scale deposits, improve heat transfer, and support the effective control of Legionella risk within hot water systems.

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Why choose Complii?

How we can help.

Protect your people, property, and business. Here’s why we’re the right choice for acid descaling.

Improved energy efficiency

Scale acts as an insulating layer, forcing boilers and calorifiers to work harder to reach the same temperature. Removing it restores optimal heat transfer and reduces energy consumption.

Enhanced Legionella control

Descaling eliminates one of the key environments where Legionella bacteria thrive – the combination of heat, scale, and stagnant water – helping maintain a safer system.

Prolonged equipment lifespan

By removing scale and corrosion, you prevent long-term damage to internal components, extending the life of calorifiers, pipework, and heating systems.

Compliance with HSG274 guidance

Section 182 of HSG274 Part 2 requires annual inspection and cleaning of calorifiers. Our descaling services ensure your system meets these obligations, with full reporting and documentation.

Reduced maintenance and repair costs

Regular descaling prevents blockages, improves flow rates, and reduces the likelihood of costly repairs or unplanned downtime.

Your questions answered.

Limescale build-up restricts heat transfer, increases energy usage, and creates conditions for bacterial growth, particularly Legionella. Descaling removes this build-up, improving both performance and safety.
Under HSG274 Part 2, calorifiers should be inspected annually and cleaned if deposits or debris are present. The frequency may be increased or reduced depending on inspection findings and system conditions.
No. When carried out by qualified specialists, the process uses carefully controlled chemical concentrations and circulation methods that dissolve scale safely without harming metal surfaces or seals.
In many cases, yes. We offer online descaling methods that allow cleaning to be completed while the system remains operational, reducing downtime.
Common indicators include poor heat performance, fluctuating water temperatures, reduced flow rates, and increased energy bills. A visual inspection may also reveal scaling or sediment within the vessel.
Yes. Scale and debris provide nutrients and surfaces where Legionella can grow. Removing them is a key preventative measure as part of a compliant water hygiene programme.

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