Switching from a Borehole to Mains Water? A Guide to the Final Connection
You’ve made the decision to switch your property’s water supply from a private borehole to the public mains. The new connection pipe is laid, the groundwork is done, and you’re ready for a more reliable, regulated supply. However, before the local water authority, such as Welsh Water or Severn Trent, will make that final connection, they will require one last, crucial step: proof that the existing pipework inside your property is clean and safe.
This is a common and often unexpected requirement that can delay projects. At Pipe Testing Services (PTS), we help homeowners, landowners, and businesses navigate this final compliance hurdle. This guide explains why this step is necessary and what the process involves.
Why Your Existing Pipework Must Be Disinfected
The primary concern for any water authority is protecting the integrity of the public water network. Your property’s existing internal plumbing, which has been supplied by a private, unregulated source like a borehole, is seen as an unknown quantity. Over the years, it may have developed a harmless internal biofilm, but it could also harbour bacteria or sediment.
To prevent any of these potential contaminants from flowing back into the public mains, the water authority needs proof that your entire system has been professionally disinfected before they will connect you. This process is a key part of the switching from borehole to mains water journey.
The 3-Step Process for a Compliant Switchover
To get the compliance documents you need, a specific sequence of work must be carried out.
Step 1: Physical Disconnection of the Old Supply
Before any disinfection can take place, a qualified plumber must physically and permanently disconnect your old borehole supply from your property’s internal plumbing system. This creates an “air gap” and ensures there is no possible route for cross-contamination between the old and new supplies.
Step 2: Full System Disinfection (Chlorination)
This is the core of the compliance process and our area of expertise.
- The Service: We perform a full system disinfection, detailed on our Chlorination Services page.
- The Process: Our technicians will carefully flush your property's entire existing hot and cold water system with a chlorinated solution. This is held for a specified contact time (typically at least one hour) to ensure that any biofilm or bacteria that may have built up is completely eradicated, from the point of entry right through to every tap and outlet.
Step 3: The Certificate of Compliance
After the disinfection is complete, you need the formal documentation to provide to the water authority.
The Process: We provide a certificate that details the disinfection process, confirming that it was carried out in accordance with UK standards like BS 8558. In many cases, a UKAS-accredited water sample is also taken after disinfection to provide impartial scientific proof of the water’s quality. For a full breakdown of what this involves, see our guide, Chlorination Certificates Explained.
What Should I Do with the Old Borehole?
Once your new mains supply is connected and operational, it is important to correctly decommission the old borehole to ensure it does not become a future contamination hazard for the local groundwater. This usually involves securely capping the borehole headworks, a task that a specialist borehole or well drilling company can assist with.
Choosing the Right Partner for a Smooth Connection
Switching from a borehole to mains water is a significant upgrade for your property. Don’t let the final compliance checks cause unexpected and costly delays. Choosing a specialist contractor like Pipe Testing Services means you get:
- Switching from a borehole to mains water is a significant upgrade for your property. Don't let the final compliance checks cause unexpected and costly delays. Choosing a specialist contractor like Pipe Testing Services means you get:
- Expertise with Water Authorities: We understand the specific requirements and standards that inspectors from Welsh Water, Severn Trent, and others are looking for.
- Peace of Mind: You get a reliable, professional service designed to get your new connection signed off without a hitch.
To discuss your requirements, schedule a consultation, or request a quote, please contact us at:
- Phone: 01922 451646
- Email: enquiries@pipetestingservices.co.uk
- Address: Unit 27 Birchbrook Industrial Estate, Shenstone, Lichfield, Staffs, WS14 0DJ
FAQs for the Borehole to Mains Switchover
How long does the disinfection process take?
For a typical residential property or small commercial unit, the on-site chlorination process can usually be completed in a few hours. If a water sample is required, the laboratory results typically take 3-5 working days to come back.
Is this disinfection process really necessary for a single house?
Yes. From the water authority’s perspective, the size of the property doesn’t change the risk. Any connection to their network requires proof of compliance to protect the public supply. The process of switching from borehole to mains water always prioritises public safety.
My existing internal pipework is very old. Is the process safe for it?
Yes, the process is safe for all standard types of pipework, including copper, iron, and plastic. The chlorine concentrations used are carefully controlled to be effective for disinfection without being aggressive to the pipe materials. The process can also help identify pre-existing issues, such as slow leaks that might be revealed during flushing. If you have any concerns, our Leak Detection Services can provide further peace of mind.
What information is on the certificate you provide?
Our certificate is a professional document that includes the date of disinfection, the chemical used, the concentrations and contact times achieved, and a statement of compliance with relevant standards. It contains all the information a water authority needs.