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Even if your current water supply looks clean, water testing may still be required to demonstrate the regime is appropriate and working well in compliance with HSG 274 and ACoP L8.


Water Microbiology can be an essential part of asset management, ensuring system integrity, water hygiene risk management and Legionella control.


As water testing experts, we report annually on over 200,000 Legionella tests, 50,000 Coliforms and E-coli tests, 200,000 Pseudomonas tests, 90,000 pool test samples and critical chemistry and physical parameter water testing.

Water testing and water quality knowledge bank

Water safety plan top tips

Read our top tips on implementing a safe drinking water plan.

Closed System Monitoring

Closed System Monitoring

The smart way to manage critical systems and prevent corrosion and system failure.


Our water testing services are designed to help with:

  • Accredited laboratory water testing and analysis: expert water microbiology and water chemistry for Legionella, Pseudomonas, Coliforms, Total Viable Counts (TVCs) and other parameters.

  • Chemical make-up of water: laboratory testing and sophisticated test and analysis of potable water, drinking water, process water and wastewater.

  • Physical parameters: testing for total and suspended solids and more.

  • Metal parameters: testing, analysis and interpretation to determine asset wear, system integrity and water quality.

  • Corrosion, scale and contaminants: water testing and analysis to reveal water quality and underlying system parameters and safety.

  • Swimming pool and spa water sampling and testing: hygiene analysis, Legionella analysis, environmental organisms growing in pool and distribution water systems, filters and biofilm.

  • Monitoring, certification and validation: latest field testing, sampling equipment and advice on appropriate sampling points and frequency. UKAS accreditation water testing and reporting.

Reasons to choose WCS Group

  • Water specialists focused across on-site testing, culture tests, water quality tests, water chemistry and microbiology
  • UKAS accredited laboratory network across the UK
  • Over 400,000 water quality and audit tests conducted annually
  • We specialise in industrial water problem-solving, analysis and interpretation
  • Expert support across Healthcare Water, Yeast and Mould Sample Analysis, Sulphate Reducing Bacteria Analysis, Suspended Solids Analysis, Potable Water Analysis, Effluent Water Analysis, BSRIA Closed System Analysis for BG50, Metals Analysis and much more

Common questions

When should I test for Legionella?

Refer to HSG 274 Part 2, page 40 onwards.

Legionella testing is recommended when:

  1. A water system is being treated with biocides and water is stored or distributed at low temperatures
  2. There is a lack of confidence in the water system integrity and degree of water quality control
  3. In accordance with the Water Hygiene Risk Assessment, if temperature control and disinfectant concentrations are sporadic and not being consistently achieved. Once the water system is brought back under control to establish and demonstrate a satisfactory ‘baseline’ in accordance with ACoP L8.
  4. There is a high risk population or critical exposure (eg hospital, healthcare premises, clinical or laboratory usage, swimming or spa pool usage, care home setting as well as public or commercial duty of care – HM Prison, public buildings, commercial offices, private landlord properties and so-on).

Property owners or managers are also required to test for Legionella across both hot and cold water systems, in systems where dead legs occur, sites containing cold water storage systems and cooling towers.

What should I test for in drinking water?

It rather depends on what you are using water for on your site and what your concerns initially are.

Sites with patient care plans will typically test for; Legionella bacteria, Coliforms, E-coli, Total Viable Count (TVC), Pseudomonas aeruginosa, Other Pseudomonas species and Staphyococcus aureus.

Sites with boreholes, wells or natural springs or in close proximity to farmland where concern may exist about contamination, will want to test for E-coli and Coliform as well as TVC to help determine water quality. Sites concerned about metals and heavy metals in their drinking water, will need to abide by regulations which are explicit about what constitutes wholesome drinking water.

Refer to The Drinking Water Inspectorate for Water Quality in England & Wales, Scotland and N Ireland as appropriate.

For sites using water treatment, there are also a range of chemical tests to detect scale, corrosion potential, strange taste, odour, staining and so-on.

When and what should I test swimming pool and spa water for?

The Pool Water Treatment Advisory Group Code of Practice (PWTAG) provides pool and spa operators with a detailed plan to ensure their pool water meets quality standards that provide a healthy experience for swimmers and bathers. All operators are required to work to the following general guidance. More specific parameters relate to bath load, operating levels, and water temperature maintained (swimming or bathing).


Total Viable Count / Aerobic Colony Count (TVC)

TVC at 37oC (24-hour incubation) reveals if the filtration systems are working satisfactorily. This should not exceed 100 cfu/ml.

Escherichia coli (E-coli)

This should be absent from a 100ml sample. Detection indicates human or animal faeces contamination.


Coliforms are related to E-coli. They should be absent in 100ml. Less than 10 cfu/100ml is acceptable provided it does not occur in consecutive samples, there is zero E-coli, ACC is below 10 cfu/ml and the residual disinfectant and pH values are within recommended ranges.

Pseudomanas aruginosa

This is a pathogen capable of growing in water at low temperatures especially in filters, deck level transfer channels, balance tanks, flexible polymetric tubing, pool covers and backwash systems. It should be absent in a 100ml sample. If detected between 10-50 cfu/ml, repeat water sampling and analysis whilst maintaining the free chlorine and pH values. If a count above 50 cfu/ml is detected, the pool / spa should immediately be closed and thoroughly decontaminated.


When disinfection and pH are not automatically monitored and controlled, daily manual testing is required (but refer to the Risk Assessment for frequency). Pool water samples for chemical analysis should be taken from a depth of 100-300mm.

Free chlorine levels

These values require validation by satisfactory bacteriological water quality standards. For pools using hypochlorite, assuming the pH value is 7.2, the free chlorine levels should be maintained at 1mg/l or below with an absolute minimum of 0.5mg/l. This assumes the pool has satisfactory microbiological monitoring results. The use of secondary disinfection (UV or ozone) can help minimise the free chlorine levels. These values can only be achieved where the pool is designed, engineered and operated well with effective pre-swim hygiene and is not overloaded.

Upper limits

Free chlorine levels above 3mg/l should not be present in any pool using hypochlorite. If this is exceeded, dosing should be reduced. If dosing has gone wrong and free chlorine reaches 5mg/l, chlorination should be stopped immediately. If free chlorine continues to rise, bathing should cease until the fault has been resolved and the residual free chlorine is under control.

Combined chlorine levels

The level of combined chlorine residuals should be as low as possible. Combined chlorine levels should be less than half the free chlorine, and no more than 1mg/l irrespective of the level of free chlorine. If the ratio of combined chlorine to free chlorine is unsatisfactory, some correction may need to be applied.

pH value

The pH values for the pool water should be maintained within the range recommended for the disinfectant being used. But a pH value of between 7.2 and 7.4 should be the target when using chlorine-based disinfectants. At levels above this range the free chlorine will not be so effective and may need to be increased.


To ensure effective coagulation and a stable pH when using acidic disinfectants, alkalinity in pool water should be maintained at a level between 80 and 200mg/l (measured as CaCO3). Alkalinity measurements should be taken weekly, using commercially available alkalinity test kits and using appropriate tablets. Dilution or dilute acid should be used to lower the levels of alkalinity in the pool water.

Calcium hardness

Pool water should be maintained for bather comfort, and the grout in the pool should withstand that water. Ideally calcium hardness should be maintained between 75 and 150mg/l as CaCO3. However, in areas with a hard water supply this cannot be practically achieved. It is therefore very important that water treatment chemicals do not further increase the calcium hardness values over and above that in the hard water make up supply. Calcium hardness concentrations greater than 300mg/l may result in the deposition of scale causing sudden changes in temperature and pH. Calcium hardness measurements should be taken weekly, using commercially available test kits with the appropriate tablets.

Total dissolved solids (TDS)

Dissolved solids are destructive at high levels and should never be allowed to rise more than 1,000mg/l greater the level in the source water. The TDS concentration should be reduced by dilution if necessary and should be measured weekly, using a commercially available electronic meter that has been calibrated against a commercially available standard.


Sulphate levels should be maintained below 360mg/l and should be measured once a week using a commercially available test kit.

Balanced water

It is important to maintain the water in balance and this is usually achieved when the pH is properly controlled. Alkalinity, Calcium hardness, TDS and temperature are also factors. The Langelier index is a formula that brings together all these factors. It makes sense to calculate Langelier weekly when measuring Alkalinity, Calcium hardness and TDS.

What are the testing parameters for metals in water?

Water is tested for metals to ensure drinking water is of high quality, to confirm limits prohibited in wastewater are being met, or to establish scale potential in water for example.


In accordance with The Water Supply Regulations (2010), you should test at point of supply (sentinels / taps) to the following maximum limits:

  • Lead (Pb) 10 µg/l
  • Boron (B) 1.0 mg/l
  • Chromium (Cr) 50 µg/l
  • Mercury (Hg) 1.0 µg/l
  • Arsenic (As) 10 µg/l
  • Cadmium (Vd) 5.0 µg/l
  • Copper (Cu) 2.0 mg/l
  • Antimony (Sb) 5.0 µg/l
  • Nickel (Ni) 20 µg/l
  • Selenium (Se) 10 µg/l
  • Aluminium (Al) 200 µg/l
  • Manganese (Mn) 50 µg/l
  • Iron (Fe) 200 µg/l
  • Sodium (N) 200 mg/l


Some industries can be heavy users of water in their operating and manufacturing processes. They are required to adhere to strict limits on what is discharged within their effluent water including metal content. We can test and advise on the following:

  • Barium
  • Lead
  • Copper
  • Molybdenum
  • Antimony
  • Selenium
  • Zinc
  • Chromium
  • Mercury
  • Arsenic
  • Cadmium


You can establish the scaling potential of water by testing and analysing metal content. In particular for:

  • Magnesium
  • Calcium
  • Strontium
  • Barium

At WCS Group, we test for chemical and microbial parameters which provide insights in to metals in water.

What are the testing parameters for closed system circuits?

Closed systems (circuits) should be tested for three parameters. The Hevasure Monitoring System provides ongoing diagnosis for all:

  1. System Integrity – Dissolved Oxygen, Pressure, Temperature, Water Make-up
  2. Water Characteristics – Conductivity, pH, Microbiological Risk
  3. Corrosion – Galvanic Currents, Crevice Corrosion