Maintaining building services systems requires careful planning. Proper water treatment protects pipework systems from corrosion and scale. The BSRIA guide provides essential technical content for facilities managers and design engineers. It outlines best practice for closed heating and cooling circuits. Following this guidance helps achieve energy efficiency and reliable system performance over many years. This introduction covers the key factors intended to improve system conditions.
What is BSRIA BG 50 2021?
BG 50/2021 is the most recent edition of BSRIA’s guide on Water Treatment for Closed Heating and Cooling Systems, replacing the earlier BG 50/2013 version.
The guide outlines the current principles and practical approaches used in water treatment for closed-circuit HVAC systems. It is designed for professionals involved in building services, including facilities managers, design engineers, installation contractors, and maintenance teams.
For facilities managers in particular, BG 50 offers practical guidance to support the selection of suitable water treatment solutions for their specific systems.
Key Takeaways from BG 50/2021 (Second Edition)
In the UK, chemical treatment remains the most widely used method for managing water quality in closed heating and cooling systems. As a result, BSRIA’s BG 50/2021 guide focuses heavily on this approach while also introducing other available water treatment methods.
BG 50/2021 also expands guidance on the responsibilities of professionals involved in managing water treatment in closed systems. This includes those who design water treatment programmes, specialist maintenance providers, day-to-day system operators, building owners or operators, and specialists responsible for remedial cleaning.
In addition, the guide updates recommended water quality testing parameters and benchmarks. These updates include the introduction of corrosion rate measurements, along with additional advice on corrosion monitoring and on-site testing methods, such as the use of water test kits.
The guide discusses several important practices, including:
Pre-treatment of system fill water
Removal of dissolved gases
pH control and management
Filtration and removal of solid particles
Electrochemical protection methods, such as galvanic anodes for cathodic protection
Prevention of bacterial growth and biofouling through the use of biocides
What’s New in BG50/2021 vs BG50/2013?
BSRIA’s BG 50/2021 introduces several updates and expanded guidance compared with BG 50/2013, particularly in system management, water quality monitoring, and technology used in closed heating and cooling systems.
System Management
In BG 50/2021, the section on system management has been expanded with more detailed guidance. It outlines what should be included in a formal Scheme of Control and recommends carrying out a Closed Loop Risk Assessment within three to six months after system handover.
The updated guide also separates water treatment responsibilities into two distinct roles:
Water Treatment Planner – responsible for designing the overall water treatment programme during the design stage, including both mechanical and chemical considerations.
Maintenance Water Treatment Specialist – responsible for the ongoing management and care of the system during operation.
In contrast, BG 50/2013 generally referred to a single Water Treatment Specialist, with responsibilities defined through a written Scheme of Control that outlined personnel roles, the treatment programme, and applicable operational limits.
Water Quality Monitoring
The 2021 edition places greater emphasis on monitoring long-term trends in water quality data, ensuring that parameters remain stable without upward trends. This approach reflects the wide variation between newer and older systems.
It also introduces several defined performance indicators, including:
Acceptable corrosion rates measured in MPY (mils per year)
An acceptable annual water loss limit of 5% of total system volume
To support this, the guide recommends installing a water meter on the system fill line to accurately track water losses.
The guide also shows broader acceptance of dip slide testing methods for monitoring Total Viable Count (TVC) and Pseudomonads, with clearly defined limits for TVC results. These are primarily intended for monitoring and informational purposes.
In BG 50/2013, microbial guidance focused mainly on Pseudomonads, with recommended limits of less than 10,000 cfu per 100 ml or 10% of the TVC result, typically set by the water treatment specialist. Testing for nitrate-reducing bacteria (NRB) was also available.
Water Sampling
The 2021 guide recommends sampling water according to BS 8552 guidance.
Typical sampling frequency includes:
Every two weeks after system handover or cleaning for the first two months
Monthly sampling as part of standard ongoing monitoring
By comparison, BG 50/2013 recommended routine monitoring in mid-life systems every one to three months, with more frequent testing immediately after handover or system modification.
Technology
BG 50/2021 recognises the growing importance of dissolved oxygen monitoring in managing corrosion caused by oxygen ingress. Continuous, real-time monitoring of key system variables is highlighted as an effective way to control this risk.
The guide also recommends including a dedicated circulation pump to maintain consistent pressure across filtration systems, regardless of overall system demand.
These technological considerations were not addressed in BG 50/2013.
Equipment
The 2021 edition also introduces additional guidance on equipment inspection. It recommends that buffer vesselsinclude access doors or panels to allow internal inspection.
This requirement was not included in BG 50/2013, although the earlier guide did reference filtration systems.
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Water Quality Assessments for Safe Water Systems
Regular water quality assessments are vital for safe operations. Water treatment companies typically perform these checks to ensure full compliance. They test for oxygen, bacteria, and proper inhibitor levels. Without accurate sampling, hidden problems can destroy closed heating and cooling systems. Facilities managers rely on these reports to make smart maintenance decisions. Consistent testing highlights minor issues before they become major faults. This proactive management keeps the building running safely and protects the overall health of the site.
Prevent Microbiological Fouling
Effective water treatment plays a key role in preventing microbiological fouling (biofouling), as well as corrosion and scale formation within closed heating and cooling systems.
When systems are not properly maintained, they are likely to operate less efficiently, consume more energy, and experience reduced performance. In many cases, this can also increase the likelihood of system failures.
BSRIA’s BG 50/2021 helps facilities managers understand how water treatment processes work, what results can be achieved when they are implemented correctly, and the potentially serious consequences that can arise when water treatment is ineffective.
Why Should You Choose Comfort Services Group for Your BG50 Compliance?
Comfort Services Group offers expert water treatment for closed heating systems. Our team understands the exact requirements of the BSRIA guide. We provide comprehensive services to help facilities managers achieve total compliance. From routine sampling to full system cleaning, we handle every detail. Our experienced staff uses industry standards to improve system performance.
We ensure your building services closed systems operate efficiently. Trust our proven methods to protect your pipework and maintain excellent water quality year-round.
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Frequently Asked Questions
Should I use VDI 2035 or BG50?
Choosing between VDI 2035 and BG50 depends on your specific installation. BG50 is the standard UK industry guidance for water treatment. It focuses on chemical inhibitors and regular monitoring. VDI 2035 is a German standard that relies more on chemical-free water control. Most UK design engineers and facilities managers prefer BG50 for local compliance. Always check your boiler manufacturer’s warranty, as typically they will specify which practice you must follow.
Do you offer building services following BG50?
Yes, we provide comprehensive building services systems maintenance that strictly follows BG50 guidelines. Our team conducts regular testing, sampling, and chemical dosing. We manage closed heating and cooling circuits to ensure they meet the latest industry standards. By applying best practice, we protect your equipment from scale and corrosion. Our services give facilities managers peace of mind, knowing their systems are safe, compliant, and highly energy efficient over many years.
Do you offer pre commission cleaning for closed systems?
Yes, we offer full pre commission cleaning for all new systems. This essential step removes dirt, grease, and debris left over from installation. Cleaning the pipework before switching it on prevents early damage and blockages. We strictly follow industry guidelines during this process. Proper pre commission cleaning prepares the network for long-term water treatment. It ensures the installation runs perfectly from day one, boosting system efficiency and protecting your investment.
