Chlorination Certificates for New Pipework and Water Connections

New pipework and supply pipes usually need proof that they've been tested, flushed and disinfected before use or connection. Environmental Compliance Services (ECS) carries out the chlorination, plus the pressure testing and water sampling that go with it. We work for M&E, mechanical and commercial plumbing contractors, developers, builders and construction firms, and we offer same day certification.

We're based in Norton Canes, Cannock, and work across London, the Midlands and South Wales (including Cardiff, Swansea and Bridgend), and the rest of England and Wales. All our engineers hold current CSCS and EUSR National Water Hygiene cards, and we have over 15 years' experience. Samples are tested by a UKAS-accredited laboratory.

Need a certificate for a connection date or handover? Call 0800 015 7870 or get a quote.

What is a chlorination certificate?

A chlorination certificate is the written record that a water system or supply pipe has been disinfected with chlorine, left for the required contact time, flushed out and checked. Water companies, main contractors and clients use it as evidence that new pipework is fit to carry drinking water before it is connected or handed over.

It often sits alongside a pressure test record and laboratory sample results. Severn Trent, for example, wants all three before the connection date, and asks for laboratory reports and test certificates rather than a "Certificate of Conformance".

What does a chlorination certificate record?

There's no single national template, but a chlorination certificate typically records:

the pipework or system treated, including pipe length and diameter
the disinfection dose (mg/l) and the standing (contact) time
the residual chlorine at the end of the standing time and after flushing
the date of disinfection.

Where the water company asks for them, it is supported by a pressure test record and laboratory results. Severn Trent's list, one of the most detailed, includes coliforms and E. coli per 100 ml, turbidity, pH, taste, odour and the laboratory's name.

When do you need a chlorination certificate?

New installations, extensions and handover

The Water Supply (Water Fittings) Regulations 1999 say that every water system "shall be tested, flushed and where necessary disinfected before it is first used" (Schedule 2, paragraph 13). BS 8558:2015 gives UK guidance alongside the BS EN 806 series, and PD 855468:2015 covers flushing and disinfecting new or extended systems in buildings.

For buildings, the HSE's HSG274 Part 2 (supporting ACoP L8) says hot and cold water systems should be cleaned, flushed and disinfected in situations including:

completion of a new installation or refurbishment
installation of new components, especially if the manufacturer pressure tested them with water
a system left unused and unflushed for a long period (HSG274 notes this can be as little as two or three weeks)
substantial alteration, or entry into the system for maintenance
sampling that shows microbial contamination.

On fit-outs and new builds, the certificate normally goes into the handover file. See internal pipework chlorination.

New water company connections

For a new supply pipe, the water company's rules decide what you need. Three examples:

Water company	When chlorination is required	What they ask for
Severn Trent	All private supply pipes 50mm or above, and pipes of any size where flood water, sewage or similar has got in	Pressure test, chlorination and sampling before connection. Certificate valid for 14 days from issue
South Staffs Water	Supply pipes 63mm in diameter and larger, over a distance of 25 metres or longer	A satisfactorily passed pressure test and chlorination certificate. Contact South Staffs Water in advance
Dŵr Cymru Welsh Water	New connections 63mm or above in diameter (regardless of length), or where Welsh Water specifies	A "Bacteriological Certificate" before connection, covering all internal and external pipework and firefighting supplies

Rules change and other water companies use different thresholds, so always check your connection offer. See mains chlorination for new connections.

How the chlorination process works

The method depends on the system and the water company's or client's specification. A typical job:

Pressure test. Some water companies require supply pipes to be pressure tested first, and we offer this as part of the job. Severn Trent, for example, requires MDPE/HPPE pipe to be tested at 1.5 times its pressure rating (12 bar for an 8 bar pipe), using the WRc Type 1 or Type 2 method, with pass criteria from IGN 4-01-03. See pressure testing.
Flush. The pipework is flushed to remove debris before dosing.
Chlorinate. For building water systems, HSG274 says disinfection is normally based on 50 ppm for at least one hour, with no less than 30 ppm free residual chlorine at the end. Lower concentrations with longer contact times are acceptable, as set out in BS 8558. For new water mains, Water UK's guidance (TGN 2) uses at least 20 mg/l free chlorine held for at least 16 hours. Where the water company has its own specification, that takes priority.
Contact time. The chlorine is held for the contact time, then the residual is checked.
Flush out. HSG274 says the disinfectant must be completely flushed out before the system goes back into use.
Sample. Where required, our engineers take water samples for analysis. See water sampling after chlorination.
Laboratory analysis. Samples are tested by a UKAS-accredited laboratory, which Severn Trent, for example, requires.
Certificate issued. The chlorination certificate is issued on the day, and sample results follow as soon as the laboratory reports them. Severn Trent also asks for confirmation that the supply pipe was capped after disinfection.

How long is a chlorination certificate valid?

It depends on the water company. Published examples:

Severn Trent: 14 days from the date of issue. The certificate must be in date on the day of connection.
South Staffs Water (self-lay mains): the final connection must be made within 14 days of sampling.
Water UK TGN 2 (new mains): if a main isn't brought into service within 14 days of a satisfactory sample, it should be flushed and re-sampled.
United Utilities and Essex & Suffolk Water: 30 days.
Welsh Water: its developer guidance doesn't state a validity period, so check with Welsh Water.

That's why Severn Trent asks customers not to chlorinate until they have their connection date. Book us once your date is confirmed, and we'll plan the work so the certificate is in date on the day.

Why chlorination certificates get rejected

Most rejections come down to one of these:

A failed sample. Severn Trent's pass criteria are zero coliforms, zero E. coli, turbidity below 2 NTU, pH between 6.5 and 9.5, non-coliforms below 100 (quantitative), and no odour or taste. Unsatisfactory results mean the pipe has to be re-chlorinated and re-tested.
Out of date. The certificate expired before the connection date.
Wrong or incomplete paperwork. A "Certificate of Conformance" instead of lab reports, or missing details such as dose, standing time or residuals.
Laboratory not accepted. Results weren't from a UKAS-accredited laboratory where one is required.
Contamination on site. Pipe ends left open, or dirt and water got in during storage or installation.

What affects the cost of a chlorination certificate?

We price every job on its details. The main factors are:

pipe size and length, and how many systems or supply pipes are involved
whether a pressure test is needed
sampling: how many samples, and what analysis the water company wants
site access, working hours, and whether the site is ready (water available, pipe ends accessible)
travel distance from our base in Staffordshire
re-tests or return visits if a sample fails or the connection date moves.

Tell us the water company, pipe size and length, and your connection date. Get a quote.

Same day certification

We issue the chlorination certificate on the day, once the job has been paid for, so you aren't chasing paperwork. Where your water company also needs microbiological sample results, we send them as soon as the UKAS-accredited laboratory reports them, so allow for this in your programme.

Areas we cover

We're based at Red Lion Avenue, Norton Canes, Cannock WS11 9QR, and cover:

London and the South East
Staffordshire: including Cannock, Stafford and Stoke-on-Trent
West Midlands: including Birmingham and Wolverhampton
The wider Midlands
South Wales: including Cardiff, Swansea and Bridgend
England and Wales: for contractors and developers with projects further afield.

Tell us the site postcode when you enquire, as your water company affects what the certificate must show.

Frequently asked questions

Do internal water systems in new buildings need a chlorination certificate?

Usually, yes. HSG274 lists completion of a new installation as a point at which hot and cold water systems should be cleaned, flushed and disinfected, with BS 8558 giving the method. Clients and main contractors normally want the certificate in the handover file.

How much does a chlorination certificate cost?

The price depends on pipe size and length, whether a pressure test and laboratory sampling are needed, site access and travel. Call 0800 015 7870 or use our quote form, and we'll price your job.

Does the water company chlorinate my supply pipe?

Usually not. Severn Trent makes it a requirement of the customer, and Welsh Water requires the developer to submit the certificate. You need a competent contractor to do the work.

Should I chlorinate before I have a connection date?

No. Severn Trent asks customers not to complete chlorination until they have a connection date, because its certificates are only valid for 14 days. Other water companies set similar time limits.

What size of supply pipe needs a chlorination certificate?

It varies: 50mm or above for Severn Trent, 63mm and larger over 25 metres or longer for South Staffs Water, and 63mm or above at any length for Welsh Water.

Is a chlorination certificate the same as a Water Regulations certificate?

No. A certificate from an approved contractor (for example a WIAPS or WaterSafe member) confirms the installation complies with the Water Fittings Regulations. A chlorination certificate records disinfection. A water company may ask for both.

What happens if a water sample fails?

The pipework has to be re-chlorinated and re-tested before the water company will connect it. We'll look at the likely cause, such as poor flushing, before treating it again.

Can you provide a chlorination certificate on the same day?

Yes. We issue the chlorination certificate on the day, once the job has been paid for. Microbiological sample results follow as soon as the UKAS-accredited laboratory reports them.

Need a chlorination certificate?

Call 0800 015 7870, email info@envirocompliance.co.uk or get a quote online. To help us quote quickly, tell us:

the site postcode and water company
pipe material, size and length (or the type of building system)
your connection or handover date
what paperwork you need (chlorination certificate, pressure test record, sample results).

Further reading: why chlorination requirements differ between water authorities

Sources

Water Supply (Water Fittings) Regulations 1999, Schedule 2 (para 12 test pressure; para 13 "tested, flushed and where necessary disinfected before it is first used"): https://www.legislation.gov.uk/uksi/1999/1148/schedule/2/made
BSI, BS 8558:2015 (complementary guidance to BS EN 806; replaces the withdrawn BS 6700): https://knowledge.bsigroup.com/products/guide-to-the-design-installation-testing-and-maintenance-of-services-supplying-water-for-domestic-use-within-buildings-and-their-curtilages-complementary-guidance-to-bs-en-807
BSI, PD 855468:2015 (flushing and disinfection of new or extended systems): https://knowledge.bsigroup.com/products/guide-to-the-flushing-and-disinfection-of-services-supplying-water-for-domestic-use-within-buildings-and-their-curtilages
HSE HSG274 Part 2 (para 2.127 triggers; para 2.135 50 ppm / 1 hour / not less than 30 ppm; para 2.137 flush out disinfectant): https://www.hse.gov.uk/pubns/priced/hsg274part2.pdf
Water UK, Principles of Water Supply Hygiene, TGN 2 (new mains 20 mg/l for 16 hours; 14-day re-sample; service pipes above 50mm disinfected): https://www.water.org.uk/sites/default/files/wp/2018/11/TGN-All.pdf
Severn Trent, "Customer chlorination, pressure test and sampling guidance" (50mm or above; 14-day validity; don't chlorinate before a connection date; UKAS lab; 1.5× pressure test, WRc Type 1/2, IGN 4-01-03; pass criteria; evidence fields; no "Certificate of Conformance"): https://www.stwater.co.uk/content/dam/stw/stw_buildinganddeveloping/st-customer-chlorination.pdf
South Staffs Water, connection requirements (63mm and larger over 25m or longer: passed pressure test and chlorination certificate). Re-check in a browser, as the page blocked automated fetches: https://www.south-staffs-water.co.uk/developer/get-connected/connection-requirements/
South Staffs Water, Self-Lay Provider User Guide, April 2026 (final connection within 14 days of sampling): https://south-staffs-water.co.uk/media/aghlhl0o/self-lay-provider-user-guide-april-2026.pdf
Dŵr Cymru Welsh Water, "Water Regulations: Information for Developers, Designers and Installers", V2 July 2025 (63mm and above chlorinated and tested regardless of length; "Bacteriological Certificate" before connection): https://www.dwrcymru.com/-/media/project/files/page-documents/help-and-advice/water-regulation/advice-and-guidance/2025/english/water-regulations-guidance---developers--installers.ashx
Dŵr Cymru Welsh Water, "Site Managers Guide to New Water Mains and Service Connections": https://developers.dwrcymru.com/-/media/Project/Files/Page-Documents/Developer-Services/Help-and-Advice/Application-Advice/Guidance-Notes/Site-Managers-Guide-Final.ashx
Dŵr Cymru Welsh Water, self-certification by WaterSafe approved contractors: https://www.dwrcymru.com/en/help-advice/water-regulations/self-certify
United Utilities disinfection guidance (certificates valid 30 days): https://www.unitedutilities.com/globalassets/documents/builders--developers-docs/advice-for-builders/disinfection-guidance-leaflet.pdf
Essex & Suffolk Water GN4 (results valid 30 days): https://www.eswater.co.uk/globalassets/customer-pdfs/developer-pdfs/2024/guidance-note-04---disinfection-of-new-supplies-rev-9.pdf
ECS confirmations (28 Sep 2026): same day certificate on payment; UKAS-accredited laboratory; all engineers hold current CSCS and EUSR National Water Hygiene cards; pressure testing offered.