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The guidance below is only applicable to healthcare facilities. Currently this only applies to a very limited number of buildings within the University's Estate. 

Equipment Required

The majority of work requires a thermometer and probe only. In some instances, de-scaling and disinfection materials are required.

The document “Equipment Required” explains the requirements.

Pictorial Guide to Common Water Assets

A guide to what common Water Assets look like has been produced. This is to help identify common Water Assets within various buildings across the estate.

Glossary of Terms


A suspension in a gaseous medium of solid particles, liquid particles or solid and liquid particles having negligible falling velocity.

Blow-Down/ Bleed-Off

Water discharged from the system to control the concentration of salts or other impurities in the circulating water; usually expressed as a percentage of recirculating water flow.


An apparatus used for the transfer of heat to water in a vessel by indirect means, the source of heat being contained within a pipe or coil immersed in the water.

CFU or Colony Forming Units

A unit of measurement used in microbiology that indicates the number of microorganisms present in a water sample. It is normally measured by the number of colony forming units (CFU) present in one millilitre of water.


An element used in disinfection.


A storage device for water

Cold Water Service (CWS)

Installation of plant, pipes and fitting in which cold water is stored, distributed and subsequently discharged.

Dead End/ Blind End

A length of pipe closed at one end through which no water passes.


Pipes leading to a fitting through which water only passes when there is draw-off from the fitting


A process which destroys or irreversibly inactivates micro-organisms and reduces their number to a non-hazardous level.

Domestic Water Services

Hot and cold water intended for personal hygiene, culinary, drinking water or other domestic purposes.

Hot Water Services (HWS)

Installation of plant, pipes and fittings in which water is heated, distributed and subsequently discharged (not including cold water feed tank or cistern).

HSG 274

HSE publication relating to Water Hygiene best practice

HTM 04

Department of Health guidance document relating to Water Hygiene best practice in Healthcare Establishments

Legionnaires’ Disease

A form of pneumonia caused by Legionella bacteria.


Type of aerobic bacterium which is found predominantly in warm water environments. (singular of legionellae).


A collective term for diseases caused by legionella bacteria


Pseudomonas aeruginosa is a Gram-negative bacterium which is harmful to certain categories of patients

Risk Assessment

A legal document required to assess the risk from Water services


Crystalline deposits that form on system surfaces or pipework. Scale normally results from a build-up of unwanted minerals, usually calcium carbonate.

Scale Inhibitors

Chemicals used to control scale. They function by holding up the precipitation process and/or distorting the crystal shape, thus preventing the build-up of a hard-adherent scale.

Sentinel Taps

For a hot water services – the first and last taps on a recirculating system. For cold water systems (or non-recirculating hot water systems), the nearest and furthest taps from the storage tank. The choice of sentinel taps may also include other taps which are considered to represent a risk.


A mucus-like exudate which covers a surface produced by some micro-organisms.


A general term for soft mud-like deposits found on heat transfer surfaces or other important sections of a cooling system. Also found at the base of calorifiers and cold water storage tanks.


The condition where water ceases to flow and is therefore liable to microbiological growth.

Subordinate and Tertiary HWS loops

Many larger circulating hot water systems have additional loops consisting of a smaller bore pipe branching from the flow leg of a principal loop to supply a group of outlets and connecting back to the return leg. In systems such as this, the smaller bore loops are the subordinate loops and the larger loops are the principal loops. Subordinate loops should be monitored ideally at a suitable return leg or from a representative outlet, to test all subordinate loops quarterly. However, large and complex HWS, for example in hospitals often have localised loops that feed only one or two outlets and these can be identified as tertiary loops.

Thermostatic Mixing Valves (TMV)

Mixing valve in which the temperature at the outlet valve is pre-selected and controlled automatically by the valve.

Thermostatic Mixing Tap (TMT)

As above but where the mixing valve is built into the tap

Total Viable Counts (TVC)

The total number of culturable bacteria (per volume or area) in each sample (does not include legionella).