Microbiological and Legionella Testing


Do I need Microbiological Sampling?

Microbiological sampling is an important feature of any control scheme. BS8554:2015 provides a number of circumstances where sampling is required:

  • one-off sampling for compliance.
  • ad hoc sampling for verification.
  • sampling for investigation.
  • random sampling and;
  • identification and implementation of schemes for commissioning, routine and investigative monitoring of water quality.

Further, W.E.T defers to BS8558:2015 which sets out a regime of 6 monthly sampling of potable storage tanks and the recommendations in ACoP L8 / HSG 274 relating to when Legionella sampling should be carried out:

  1. Systems treated with biocide where storage and distribution temperatures are outside acceptable parameters.
  2. In systems where the control measures are not consistently achieved.
  3. Where a Legionella outbreak is suspected (download action levels from ACoP L8).
  4. High risk areas where the users of water systems are in a highly susceptible category e.g. hospital wards with immunologically compromised patients.

What is involved during Microbiological sampling?

W.E.T can test for over 50 different types of microbiological and water chemistry analysis.

The locations of the samples and the procedure for testing is predetermined by W.E.T’s compliance team by using their experience and reference to guidance such as BS8680:2020, as this is crucial to ensure correct interpretation of any results.

W.E.T’s technicians will perform the sample collection on site using the methodology provided by the company’s City & Guilds training, designed to achieve standards such as BS7592:2008, before passing the samples on to an independent UKAS laboratory for analysis.

The most common microbiological samples are:

Test Analysis period Purpose
Dip slides 24 – 72 Hours Semi-quantitative measurement for the general presence of bacteria in water.
TVC - Total Viable Counts 2-5 Days Basic test of water quality.
Determines overall levels of contamination.
Essential that TVC falls within recommended guidelines for the control of Legionella.
Coliforms 24-72 Hours Indicates potential contamination of water source.
Evaluates general quality of the water.
Two Types: Coliform and Faecal Coliform.
Coliform – indicates water pollution.
Faecal Coliform – indicator of water contamination from human and other warm blooded animals' waste products.
E-Coli 24-72 Hours Coliform bacteria are used to indicate the presence of other bacteria.
E-Coli does not live very long in water so is an indication of recent contamination.
Their presence also indicates the possibility of similar bacteria also being present.
Legionella 2 Weeks Legionella is commonly found naturally water systems; an increase to harmful levels can cause Legionnaires’ disease.
Legionella sampling is required under ACoP L8 guidelines to identify systems which may pose a risk.
Pseudomonas Up to 7 Days Appropriate to test for in certain water systems.
It is a common environmental organism which easily colonises water systems and can produce a biofilm which affect taste and colour of water. Harmful levels can cause severe infection; particularly in immunocompromised people.

Why choose W.E.T for your Microbiological sampling?

  • Strictly compliant:
    All microbiological samples are taken, transported and analysed under UKAS accredited conditions as stipulated by ACoP L8 to keep you compliant.
  • Experience:
    Over 500 samples are taken and tested each year by our engineers, overseen by an operational management team qualified in Microbiology so you can be reassured of our experience and qualification.
  • Record keeping:
    Each sample is issued a unique reference and is logged on an online portal so we can trace their status. Full reports are then interpreted and issued by our dedicated account management team to ensure your records are compliant.
  • Responsive and reassuring:
    In the event of any out of range results, we have strict procedures in place to remedy the situation, fast tracking action where possible and responding to site usually within 24 hours to minimise any required system shut down.
  • Quality standard:
    All testing is undertaken using equipment, which has been pre-calibrated in accordance with UKAS accredited test methods and managed under our quality standard ISO 9001:2015 to ensure your results are recorded accurately, every time.
  • Accredited by the Legionella Control Association:
    Services are carried out under internal procedures which have been accredited by the Legionella Control Association to ensure year round compliance and quality of service to our clients.
  • National Water Hygiene Card Holder:
    All W.E.T engineers are National Water Hygiene Card holders, which is recognised by all UK water companies and is a pre-requisite for any work on the water distribution network.
Our friendly and experienced customer service team are here to help you.


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