Monitoring & Maintenance of Domestic Water Systems

Cleanliness, water quality and microbiological control are essential factors in the safe operation of engineered water systems, and maintaining good domestic system water quality. As specialists in the field of water hygiene ph Water Technologies Ltd provide not only traditional methods of monitoring, cleaning, disinfection and refurbishment of domestic and process water systems, but also innovative control systems. All systems and practices are designed to meet specific site requirements for industrial, commercial, leisure and healthcare premises. All working methods and control systems comply with the latest Codes of Practice and specifications.

Typically the systems to be considered are:

  • Cold water storage tanks
  • Cooling towers
  • Evaporative condensers
  • Domestic water tanks/systems.
  • Calorifiers and water heaters
  • Air handling units
  • System pipework

Where is legionella found?

Legionella bacteria are common in natural water courses such as rivers and ponds. Since legionella are widespread in the environment, they may contaminate and grow in other water systems such as cooling towers and hot and cold water services. They survive low temperatures and thrive at temperatures between 20°C- 45°C if the conditions are right, e.g. if a supply of nutrients is present such as rust, sludge, scale, algae and other bacteria. They are killed by high temperatures. It is therefore important to control the risks by introducing measures outlined in the Approved Code of Practice & guidance document Legionnaires’ disease – The Control of Legionella Bacteria in Water Systems (L8).

What are my duties under the law?

As an employer or a person in control of the premises (eg a landlord), under general health and safety law, you have to consider the risks from legionella that may affect your staff or members of the public and take suitable precautions.

ACoP L8 4th Edition

There have recently been a number of high profile cases of Legionnaires disease. All businesses have an obligation to take the correct measures to protect their staff, customers and the public against the risk of Legionnaires disease. The Code of Practice and Guidance called L8 was designed to help businesses meet their legal obligations.

British Standard BS 8558:2011

Samples should be sufficient in number to be fully representative of the distribution system, sub-branches, tanks and cisterns as well as the condition to be evaluated, e.g. completion of a cleaning process, efficacy of distribution of disinfectant; and taken at a frequency which is representative of the time series to be demonstrated, e.g. taking into account the growth rate of the organism when designing the monitoring scheme to check for potential microbiological colonization.

Sampling and Monitoring Quality Assurance

Regular sampling practice audits should be carried out to ensure that a responsible person can verify the cleaning process or monitoring programme as part of a building water safety plan (see the WHO’s Water safety in buildings [28]). Water quality sampling practice should be audited in accordance with BS 8550

HSG274 & BS8558 Guidelines for Cold Water Storage Tanks

Regular inspections of the tank and microbiological sampling are specific requirements of HSG 274 and BS8558 (previously BS6700) to remain compliant with the HSE’s ACoP L8.

To help you understand the guidelines ph Water have devised the table below:

*Potable cold water storage tanks are those which feed drinking water outlets
** Annually or more frequent if inspection deems necessary

This table should be used as a guide only. If you are responsible for the health and safety of a water system you should carry out a risk assessment to determine the frequency of any controls or seek professional advice.

The perceived risk level should determine the frequency of sampling and locations. We would recommend that (as a minimum) samples are collected on a six monthly basis and the locations include: incoming main; Cisterns; Calorifiers; showers, sentinel Hot and sentinel Cold water outlets.


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