Understanding Chlorination Certificates
What Is a Chlorination Certificate? Legal Requirements and Standards in the UK
Ensuring the safety and quality of water is paramount for public health. Chlorination plays a vital role in the water treatment process, helping to disinfect drinking water systems and prevent the spread of harmful microorganisms and waterborne diseases. In this blog post, we explore what a chlorination certificate is, whether water chlorination is a legal requirement in the UK, why new pipework must be chlorinated, and the standards and substances used in effective water treatment.
What Is a Chlorination Certificate?
A chlorination certificate is official documentation verifying that a water system has been successfully disinfected using chlorine disinfection. The certificate includes:
- Date of chlorination
- Form and amount of chlorine used (e.g., sodium hypochlorite, calcium hypochlorite, or chlorine gas)
- Contact time
- Measured chlorine residual (free and combined chlorine)
- Relevant test results
This certificate confirms the water system meets the necessary public health and safety standards, reducing the risk of possible misuse or abuse situation where unsafe water could enter the supply.
Is Water Chlorination a Legal Requirement in the UK?
Yes, water chlorination is legally required in specific scenarios under the Water Supply (Water Quality) Regulations 2016. The regulations mandate effective disinfection of water systems to ensure safe clean drinking water for consumers.
When is chlorination required?
- Installation of new or replacement pipework
- Changes to raw water sources
- After repairs to existing systems
- In water treatment plants
- During commissioning of new drinking water systems
What legislation applies?
For comprehensive information, refer to the Drinking Water Inspectorate (DWI) and the Water Regulations Advisory Scheme (WRAS). Their guidance covers procedures, chlorine demand calculations, and testing for chlorine residuals to meet compliance.
Does New Pipework Need to Be Chlorinated?
Yes. New pipework must be chlorinated before entering service. This is known as shock chlorination, a high-strength dose designed to eliminate any harmful microorganisms that may have been introduced during installation. Proper chlorine disinfection of new pipework ensures that the system starts off pathogen-free.
After shock chlorination, the system is flushed, and tests are carried out to ensure free chlorine levels are safe and effective. The final step is issuing a chlorination certificate, confirming the process was completed to standard.
What Are the Standards for Water Chlorination?
International Guidelines
World Health Organization (WHO) – Offers globally accepted drinking water quality guidelines, including advice on the effectiveness of chlorine, chlorine residual levels, and use of compounds like hypochlorous acid and chloramines.
British Standards
BS 8558 – Guidance on design, installation, testing, and maintenance of water systems
BS 8680 – Code of practice for water safety planning in buildings
These standards define methods such as breakpoint chlorination, where enough chlorine is added to react with all combined chlorine (including dichloramine) and ensure only free chlorine remains for ongoing protection.
Common Forms of Chlorine Used
Different forms of chlorine are used depending on the application:
- Sodium hypochlorite (liquid bleach) – Common in both domestic and industrial settings
- Calcium hypochlorite (solid pellets or powder) – Often used for shock chlorination
- Chlorine gas – Used in large-scale water treatment plants
- Hypochlorous acid – A highly effective disinfectant formed when chlorine dissolves in water
All of these compounds work by oxidising cell walls of microorganisms and must be carefully monitored to avoid under-dosing or overdosing.
Why Is Chlorine Monitoring So Important?
Maintaining the right chlorine residual is key for effective disinfection. Too little and pathogens may survive; too much, and clean drinking water may develop a bad taste or pose health risks. Testing ensures that:
- There’s enough chlorine for ongoing protection
- The chlorine demand of the system has been met
- Water meets public health standards
Security, Safety, and System Compliance
In today’s world, access to safe water is critical, and water systems must be protected from possible abuse, security issues, or a virus or attack. Proper chlorine disinfection, documented with a chlorination certificate, is a key part of this protection strategy.
Sometimes, technical issues (like a server or client error) can prevent access to digital chlorination records. In such cases, system administrators must ensure offline copies are stored safely and compliant with auditing requirements.
Why Choose H2O Comply for Your Chlorination Certificate?
At H2O Comply, we specialise in effective water treatment and disinfection services that comply with all UK regulations. Our chlorination services use proven methods and tested forms of chlorine to ensure your water system is safe and fully certified.
Whether you need tank disinfection, shock chlorination, or a full system flush, our team ensures:
- Reliable service
- Rapid turnaround for certification
- Full compliance with BS 8558, BS 8680, and DWI guidance
- Peace of mind
Get Certified Today
Don’t leave your compliance to chance. Partner with H2O Comply for efficient, expert water chlorination certification.
👉 Contact us now to safeguard your drinking water systems and ensure you’re fully compliant.
Blog Updated 12/05/2025
Useful resources
https://www.who.int/publications/i/item/9789241549950
Podcast: Understanding Chlorine Certification
Get the facts on chlorine certification from the experts. We cover what you need to know about getting certified, handling chlorine safely, and staying compliant with regulations. Perfect for pool operators, water treatment staff, and anyone working with chlorine who needs to get certified.
