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Recommissioning a Commercial Water System

A guide to recommissioning a commercial water system by Pipe Testing Services, over a background photo of a professional chemical dosing system in a plant room.

Recommissioning a Commercial Water System

    You’ve just taken over the lease on a new commercial property; perhaps a bar, a care home, or a small business unit. Before you can open your doors to the public, one of the most important safety checks is on the water system. If a building has been inactive for an extended period, the stagnant water in its pipes and tanks can become a serious health hazard.

    Simply flushing the taps is not enough. A formal recommissioning process is essential to protect your staff and customers and to ensure you comply with UK health and safety regulations. At Pipe Testing Services (PTS), we guide businesses through this process every week. This guide explains the key steps you need to take.

    The Hidden Risks in Stagnant Water Systems

    When water sits unused in pipes, it creates the perfect environment for biofilm—a slimy layer of microorganisms—to develop. Within this biofilm, dangerous bacteria like Legionella can multiply to dangerous levels. The Health and Safety Executive’s ACOP L8 guidance makes it clear that building owners have a legal duty to manage this risk. A thorough recommissioning process is the definitive way to do this.

    A 4-Step Checklist for Water System Recommissioning

    To ensure your property’s water is safe and compliant, we follow a proven, four-step process.

    Step 1: Conduct a Legionella Risk Assessment

    This is the mandatory first step. Before any cleaning or disinfection work begins, a competent person must survey the water system to identify potential hazards.

    Step 2: Clean and Disinfect Water Storage Tanks

    If your property has a cold water storage tank, it is the most likely source of contamination and must be addressed first.

    Step 3: Perform a Full System Disinfection

    Once the main storage is clean, the entire hot and cold water distribution network needs to be disinfected.

    Step 4: Provide Proof of Compliance

    After the disinfection is complete, you need formal documentation to prove the process was successful and that the system is safe to use.

    Don't Forget Your Other Pipe Systems

    While domestic hot and cold water systems are the priority for Legionella, other pipework in a commercial building may also need attention after a period of inactivity. We are often asked about assessing the integrity of commercial heating pipework (LTHW). If you have concerns about the condition of these systems, you can learn more in our Guide to Testing Different Pipe Systems.

    Choosing the Right Partner for a Safe Opening

    Recommissioning your new property’s water system is a critical step in preparing for a safe and compliant opening. Choosing a specialist contractor like Pipe Testing Services means you get:

    PTS Supports Sapphire Utility Solutions on Severn Trent Water's AMP7 Mains Renewal

    To discuss your requirements, schedule a consultation, or request a quote, please contact us at:

    Recommissioning FAQs

    How long does the recommissioning process take?

    For a small-to-medium commercial property, the on-site cleaning and disinfection can often be completed in a single day. However, if water samples are required, the final laboratory results can take 3-5 working days to come back.

    Yes. Under UK health and safety law, all business owners and landlords have a duty of care to ensure their water systems are safe. For properties with stored water or those open to the public, a formal recommissioning process after a period of inactivity is considered a key part of fulfilling that duty.

    If a risk assessment or a previous test has identified Legionella, the cleaning and disinfection process is mandatory. Our expert Legionella Contractors can manage this as a full remedial action.

    Due to the use of hazardous chemicals, the need for specialist equipment, and the requirement for compliant documentation, this work should always be carried out by trained and competent professionals.