Ground Source Heat Pump Installed? It’s Time to Rethink Your Legionella Control Strategy
The installation of air and ground-source heat pumps is playing a key role in decarbonisation strategies across the UK.
Councils, housing associations and commercial estates are transitioning away from gas-fired boilers to reduce emissions and future-proof their heating systems.
It’s the right move environmentally. But it requires a rethink when it comes to Legionella control.
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The Challenge: Lower Temperatures, Higher Risk
Traditional gas boilers routinely operate at:
• 70–80°C radiator flow temperatures
• 60°C+ calorifier temperatures
These higher temperatures alone are generally sufficient to control Legionella.
Heat pumps, by design, operate at significantly lower water temperatures — typically 35–55°C.
This reduces the system’s ability to suppress Legionella through temperature alone.
Pictured Left: Legionella is a type of bacterium found naturally in freshwater environments that can cause serious, sometimes fatal, pneumonia (Legionnaires' disease) and a milder flu-like illness (Pontiac fever) when inhaled via contaminated water droplets or mist.
A Real Site Example and Where SafeSol Stepped In
SafeSol were brought in to support a site following the installation of a ground source heat pump.
Before the installation of the ground source heat pump:
• Calorifier flow temperatures were consistently 60°C
• Tap temperatures exceeded 50°C
• Legionella control was stable
After installation of the ground source heat pump:
• Hot water temperatures were reduced at both the calorifier and outlets
• Daily immersion heating was introduced for one hour per day to raise temperatures to 65°C+ in an attempt to manage legionella risk
• Despite this, routine sampling kept returning positive Legionella results.
The site:
• Reviewed its risk assessment
• Performed further immersion heating cycles
• Carried out a full system disinfection using Huwa-San with SafeSol's assistance
Initially, results improved. But over time, positive Legionella samples reappeared. A more resilient, continuous strategy was required.
The Solution: Huwa-San Constant Dosing
SafeSol designed and implemented a Huwa-San constant-dosing system tailored to the site.
This system:
• Uses a precision dosing pump
• Introduces silver-stabilised hydrogen peroxide proportionally to incoming water flow
• Maintains a consistent level of disinfectant residual throughout the system to successfully combat legionella risk
• Provides 24/7 microbiological protection
Unlike thermal boosting, constant dosing:
✔ Does not rely on short high-temperature windows
✔ Protects during stagnation periods
✔ Destroys biofilm - where the legionella bacteria thrives
✔ Ultimately, supports compliance in low-temperature heat pump environments
It becomes a secondary barrier when temperature control cannot be consistently achieved, which is increasingly the case with air- and ground-source heat pumps.
Since installation, the site has achieved sustained Legionella control.
Why SafeSol’s Involvement Matters
Constant dosing isn’t simply about installing a pump. It requires:
• System assessment
• Correct sizing and dosing calculation
• Integration with incoming mains supply
• Ongoing monitoring strategy
• Compliance alignment with HSG274 and risk assessments
SafeSol were involved at every stage - from diagnosis and corrective action through to system design and implementation.
This level of technical input is critical to ensuring:
• Correct dosing levels
• Effective residual maintenance
• Long-term stability
• Audit-ready compliance documentation
We don’t just supply Huwa-San We design, implement, and support comprehensive water-safety strategies tailored to modern heating systems.
The Bigger Picture
As more organisations adopt heat pumps, we expect to see:
• Increased reliance on immersion boosting
• Greater variability in water temperatures
• Rising microbiological risk if strategies aren’t adapted
The installation of a heat pump should trigger a Legionella strategy review. If your site has moved to low-temperature heating, or is planning to, now is the time to consider whether temperature control alone is still sufficient.
Future-Proof Your Legionella Control
Huwa-San constant-dosing provides continuous protection that many ground source systems require.
SafeSol provides the technical expertise to design and install it correctly.
If you’re operating air- or ground-source heat pumps and want a resilient, compliant solution for legionella control - speak to SafeSol’s technical team.
Decarbonise with confidence, without compromising water safety.
Huwa-San constant-dosing provides continuous protection that many ground source systems require.
If you’re operating air or ground source heat pumps and need a more resilient Legionella control strategy, SafeSol can help.
For expert advice on Huwa-San constant dosing systems:
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