HTHW Boiler Water Treatment: Why BG02 and BG04 Guidance Matters
High-temperature, high-pressure hot water (HTHW) boilers are critical assets in many industrial and commercial operations.
But with high temperatures and pressures comes increased risk — and that means water treatment must be right from day one.
To ensure safe, reliable, and efficient operation, industry guidance such as BG02 and BG04 plays a vital role.
What Are BG02 and BG04?
BG02 and BG04 are guidance documents produced by the Combustion Engineering Association (CEA).
Used together, they provide a framework for:
- Safe operation of HTHW and steam boiler systems
- Effective water treatment and monitoring
- Long-term protection of plant and equipment
These documents are widely recognised across the UK as best practice guidance for boiler management.
Why Water Treatment Is Critical in HTHW Systems
Unlike low-temperature systems, HTHW boilers operate under conditions where poor water quality can rapidly cause damage.
Without proper control, issues such as corrosion, scaling, and fouling can develop — leading to:
- Reduced efficiency
- Increased energy costs
- Premature equipment failure
- Safety risks
This is why proactive water treatment and monitoring is essential.
Key Principles from BG02 and BG04
BG02 and BG04 reinforce several core principles that protect HTHW systems over the long term:
✅ Correct Water Chemistry Control
Maintaining appropriate pH levels and inhibitor dosing is critical to prevent corrosion and protect system materials.
✅ Keeping Systems Clean
Systems must be kept free from:
- Sludge
- Debris
- Contamination
Clean systems improve heat transfer and reduce the risk of blockages and localised overheating.
✅ Minimising Oxygen Ingress
Oxygen is one of the primary drivers of corrosion in HTHW systems.
Control measures include:
- Preventing air ingress
- Managing system top-up water
- Ensuring proper deaeration where applicable
✅ Monitoring and Trending
Routine testing is not enough on its own.
Operators should:
- Monitor key water quality parameters
- Track trends over time
- Act early when corrosion indicators or deviations appear
Early intervention prevents small issues from developing into major failures.
Protecting Your Boiler Investment
A new HTHW boiler represents a significant capital investment.
Without the right water treatment regime, that investment can quickly be compromised.
By aligning with BG02 and BG04 guidance, organisations can:
- Extend equipment lifespan
- Maintain system efficiency
- Reduce maintenance costs
- Improve operational reliability
- Ensure compliance with best practice
Commissioning and Ongoing Support
Whether you are:
- Commissioning a new HTHW boiler
- Reviewing an existing system
- Looking to improve performance and compliance
It is essential that your water treatment programme and monitoring strategy are fit for purpose.
At Deep Water Blue Ltd, we support organisations with HTHW water treatment, system reviews, and operator training, helping ensure systems are protected from day one.
Because effective water treatment isn’t just about performance — it’s about safety, reliability, and protecting your investment.
