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LTHW And Chilled Pipework Connections To An Office FCU

Closed hot and cold water circulating systems within large buildings

Controlling the office environment is paramount to maintaining a happy and productive workforce. One important factor is the ability of the building’s systems to control the temperature of the workspace.

Most of the time, these hidden heroes work away in the background, keeping the temperature ‘just right’, like Goldilocks’ porridge. Happy days!

But when a hot and cold-water circulating system fails, everybody notices. The complaints come pouring in and solutions are needed fast; a loss of control of temperature within the working space is a leading cause for complaints and quickly becomes a major priority for the building management, so it makes sense to have robust maintenance regimes in place.  

Circulating hot or cold-water systems

A common, cost-effective and efficient way of achieving a comfortable temperature year-round is by maintaining circulating hot and cold-water systems, usually in the form of a centralised LTHW (low temperature hot water system), and a chilled water system. LTHW and chilled systems are circulated through the office areas where they often feed fan coil units, providing the heat exchange location.

What is a Fan Coil Unit? (The technical bit)

Fan coil units are essentially a box mounted into the ceiling void. As well as containing a fan, the unit also has two heat exchange surfaces, one connected to the chilled system and the other to the LTHW system.

Air is moved by the fan from the ceiling void across either the heating or cooling coil before being distributed back into the office areas via multiple ducted air supplies.

The rate at which the heat can be added or removed from the environment is proportional to the difference in temperature at the heat exchange surface and the flow rate of air across it. Large temperature differences at the heat exchange surface, can achieve big changes in the temperature of air flowing across it. Likewise, the temperature differences at the heat exchanger surface, on the water side, are directly proportional to the temperature that the water system is maintained at and the rate of flow through the heat exchanger.

As with most plant in large commercial buildings, these water systems can be highly complex with a large variety of flow control devices. Some control flow locally, using temperature or pressure and others are connected to the building’s BMS (Building Management System). 

When the system fails

Like any complex system, these units can fail from time to time. Water quality is often assumed to be the culprit, although there can be other causes (poor design, lack of maintenance or inadequate commissioning, for example). It’s true that water quality can deteriorate over time, leading to reductions in flow within the system and reduced temperature control in the work environment. That’s why on-going prophylactic water treatment maintenance of such systems is essential.

If your system fails and water quality is determined to be the cause, you will want a specialist water treatment contractor such as Dantek to flush the system. In my next post, I will explain the process and offer some advice on the best ways to manage it and get your building’s ambient temperature back to ‘just right’!

Please contact Dantek for further information on how we can help guide you through a successful flushing project within your building.


Children Washing Hands At School

Legionella control case study at a large boarding school

Dantek have provided legionella control services to Marlborough College for a number of years, below is a case study about how we work together to ensure ACoP L8 compliance and the safety of the students and staff.

Since its establishment in 1843 by a group of Church of England clergymen at the Castle Inn at Marlborough, Marlborough College has never been frightened of change. 

In its recent history, numerous academic initiatives have been fostered at the College including, Business Studies, SMP Maths, Combined Science, Pre-U examination syllabuses and the teaching of Arabic and Chinese. In 1968 Marlborough was one of the first of the traditional boys’ boarding schools to admit girls into the Sixth Form.

In 1989, the College became fully co-educational with the admission of girls into the Lower School and with the establishment of the first of the all-girl boarding houses.

Today the College caters for 936 pupils (of which just over 40% are girls) and the great majority of whom (98%) are boarders.  The remaining four “Out-College” houses accommodate 13-16-year-old boys, plus a mixed Sixth Form of both girls and boys.

School size: 201-500 employees

Based at: Marlborough, Wiltshire

The support Dantek provides

As a school, Marlborough College provides care for a large group of students most of which board on site, this means that they must adhere to strict health and safety guidelines. One of these areas is the need to protect students and staff from potential Legionella infection. Dantek has worked with the school for many years ensuring they comply with all regulations thus providing a safe environment for their students to thrive in.

As part of their on-going activity, Dantek engineers monitor the water quality, carry out remedial work and run regular testing and Legionella risk assessments. The College compliance team benefit from using Dantek’s electronic logbook which saves time and helps them keep on top of the various requirements. Dantek has provided a long-standing service to the college and act as part of their team which supports the quality of environment and interaction required by the College.

What does the client say?

We caught up with Kelvin Neale, M&E and Energy Manager at Marlborough College to find out how he views working with Dantek;

How did you hear of Dantek?

I have worked at Marlborough College for 8 months so Dantek were already in place when I joined. However, I did work with Dantek through another employer. I can certainly say that Dantek are known for their sound reputation in the industry.

What are the most important elements you look for in a contractor?

The most important elements for me are timely communication and a conscientious, effective manner. Due to the nature of the work Dantek provide, I also look for clear paperwork and accurate paper trial. We do consider the price, but it is not the only factor. When it comes to compliance, we must make sure we are choosing the right supplier who has the knowledge and systems which we require.

What do you like about working with Dantek?

I am very happy with their work in general. Three things stand up for me in particular:

  1. All engineers are professionals and knowledgeable, DBS checked and employed directly. They will always provide a service that goes beyond their contractual requirements and nothing we ask is ever an issue.
  2. The level of knowledge and expertise the company holds is impressive, they clearly know their stuff. I am also very impressed with the fact that on the rare occasion when they come across something they don’t know; they will go away to research for the right solution. It really demonstrates how competent they are and allows me to trust their advice implicitly.
  3. The electronic logbook is helpful and saves me a lot of time. It means I always have the data I need available to me and we never miss any tests and activities we need to complete.

How do they stand out against the competition?

As mentioned before, Dantek has a strong reputation in the industry. I think the main elements that make them stand out for me are as follows:

  1. The concise and timely completion of every job
  2. The electronic logbook which allows me to stay on top of compliance requirements, documentation and paperwork
  3. The level of knowledge and expertise they demonstrate about water treatment and legionella control


Cleaning And Chlorination Of Cooling Tower

Cooling tower water treatment – FAQ’s

What do I need to do if I am responsible for a cooling tower?
The first step is to carry out a Legionella Risk Assessment, it will need to be conducted by a competent water treatment professional with expertise in cooling towers. The risk assessment will form the basis of control measures put in place to reduce the risk of legionnaires’ disease.

You will also need to register the Cooling Tower with your local authority.

(The Notification of Cooling Towers and Evaporative Condensers Regulations 1992). These Regulations require employers to inform their local authority, in writing, if they operate a cooling tower or evaporative condenser and include the location of the tower to be used in case of an outbreak of Legionnaires’ disease. It is also a requirement for employers to notify when cooling towers are no longer in use. Notification forms are available from your local environmental health department.

What are cooling towers used for?
Cooling towers provide cooling for a wide range of industrial processes and air conditioning.

Cooling tower means a device whose main purpose is to cool water by direct contact between the water it holds and a stream of air.

Evaporative condenser means a device whose main purpose is to cool a fluid by passing the fluid through a heat exchanger which is itself cooled by contact with water passing through a stream of air.

Essentially, they are both arranged so that the air moves against the direction of the water.

The process of using evaporative cooling of water is widely used to deplete heat from air conditioning, refrigeration and industrial process systems. There are a range of evaporative cooling systems that use the evaporation of water to achieve this cooling effect and these include cooling towers and evaporative condensers. Open-circuit cooling towers are the most common and range in size from small packaged towers used in air conditioning and light industrial sites, up to large towers, including hyperbolic towers for heavy industrial uses.

Water boils at 100℃ and freezes at 0℃ and these changes of state from liquid to steam require an additional input of energy known as the latent heat of vaporisation.

The energy required to change 1 gram of water into steam is the highest of any known liquid which makes it particularly good as a cooling medium. As the water evaporates it takes a large amount of energy with it which cools the remaining liquid considerably.

Why cooling tower water treatment is needed?
The water used in cooling towers needs to be treated because impurities in the water cause the following problems all of which require actions for the system to run efficiently:

  • Scale
  • Corrosion
  • Suspended solids
  • Microbiological growth

It is important to have in place an effective water treatment programme to prevent the growth of legionella in the cooling water. A cooling tower water treatment programme should be capable of controlling not only legionella and other microbial activity but also corrosion, scale formation and fouling to maintain the system’s cleanliness. Appropriate water treatment may involve a range of chemical and physical techniques to control corrosion, scaling and fouling potential of the cooling water and to control microbial growth. Any water treatment regime must be monitored regularly to ensure they remain effective. The exact techniques that are required may vary significantly with different water supplies, the design of the cooling system and local operating conditions so it is important to engage a water treatment consultant to ensure the correct selection of control measures for your site.

How do you prevent legionnaires disease in cooling towers?
The first action is to identify and assess the sources of risk and appoint an individual who is managerially responsible for the system. This person must be trained and competent and must also have the authority and budget to act when necessary. The next step is to prepare a written scheme to include temperature monitoring, chemical treatment and any remedial works required to ensure compliance with current guidance. Once a scheme has been prepared it needs to be implemented, managed and monitored. Information must be held in a logbook so records are accessible and can be used to check the scheme remains effective. The records must be regularly reviewed, and any changes made to ensure effectiveness. Records must be kept for 5 years.

It is a legal duty to control the risk of exposure to legionella bacteria. As legionella bacteria are more likely to grow and proliferate in a cooling system fouled with sludge, scale and other deposits, maintaining system cleanliness and the water in it is an essential part of the control regime. The cleaning and disinfection frequency must be determined by a risk assessment and this should be based on inspection and the history of the water treatment control of microbial activity, scaling tendencies and other factors that may result in fouling of the system. In relatively clean environments with effective control measures, it may be acceptable to extend the period between cleaning operations, provided you can demonstrate that system cleanliness is maintained.

Water quality monitoring
The composition of the make-up and cooling water must be routinely monitored to ensure the continued effectiveness of the treatment programme. The frequency and extent will depend on the operating characteristics of the system. There are some checks which must be carried out weekly for example TDS and pH, while others are much less frequent for example legionella testing which is typically carried out quarterly.

Routine checks on cooling towers:

There are various checks which must be performed daily; these include a visual check of the cooling tower, check on the internal condition, dosage equipment and chemical drum levels check.

Every week the oxidising biocide levels, conductivity (TDS), pH, microbiological activity, pumps and softener must be checked and records updated in the logbook.

Why is scale a problem is cooling towers?
Scale is one of the four main issues found in cooling towers below are 5 of the key implications of scale:

  • Scale reduces heat transfer
  • Scale promotes corrosion
  • Scale promotes microbial growth for example legionella bacteria
  • Scale absorbs chemical treatments
  • Scale can obstruct pipework causing inefficiency and increased energy costs

Scale is the localised build-up of normally water-soluble inorganic hardness salts. Its formation is influenced by the concentration of calcium salts, pH, surface and bulk water temperatures and the concentration of the total dissolved solids (TDS). As an evaporative cooling system operates, the concentration of these various dissolved solids increases and the pH of the water tends to rise, which results in the scaling potential of the water increasing.

Scale formation results in loss of heat transfer, reduced flow rates and loss of efficiency and contributes to deposition. Legionella can be associated with such deposits. The scale protects the bacteria and so reduces the effectiveness of any biocidal treatment.

One or more of the following techniques generally control scale formation:

  • removing the hardness from the make-up water by pre-treatment, e.g. water softening
  • adding specific scale inhibitors that extend the solubility of the hardness salts and so prevent precipitation
  • acid dosing to lower the pH and alkalinity and reduce the scaling potential
  • limiting the system concentration factor to a range within which the hardness salts can remain soluble

What is TDS in a cooling tower?
Conductivity or Total dissolved solids (TDS) the quantity of solids dissolved in the water, measured in mg/l. These solids will typically include calcium and magnesium (sodium in softened water), bicarbonate, chloride, sulphate and traces of other materials. TDS indicates general water quality.

What are dipslides used for in cooling towers?
Dipslides are used to measure the level of bacteria. They are incubated at 30°C for 48 hours and bacteria will show as red spots. A comparison chart is used to assess the level of bacteria.

For further information about water treatment service contracts for cooling towers contact us to talk through how we can help keep your cooling tower running efficiently and compliant with the latest HSE guidance for Legionella control.

Frequently asked questions about Legionella control

Legionella control FAQ’s

What is Legionnaires’ Disease?

Legionnaires’ disease is a potentially fatal pneumonia caused by inhaling legionella bacteria.  Infection is caused by breathing in small droplets of water contaminated by the bacteria in the lungs.

Legionellosis is the term used to describe the diseases caused by legionella bacteria, of which Legionnaires’ disease is potentially fatal.  Pontiac fever and Lochgolihead fever are the less serious conditions but none the less avoidable if the correct cause of actions is taken.


Who can catch Legionnaires’ disease?

Everyone is potentially susceptible to infection, but some people are at higher risk e.g. those over 45 years of age, smokers and heavy drinkers, those suffering from chronic respiratory or kidney disease, and people whose immune system is impaired.


Where is legionella found?

Legionella bacteria (legionella pneumophila) are common in natural water courses such as rivers and ponds.  Since legionella are widespread in the environment, they may contaminate and grow in man-made water systems such as cooling towers and hot and cold-water services.  Spa baths, Jacuzzi’s and hot tubs are also provide a potential breeding ground for legionella bacteria as they provide optimum conditions for the bacteria to grow and multiply to sufficient numbers for a system to be colonised.

The bacteria thrive at temperatures between 20 and 45 degrees, particularly if there is a supply of nutrients such as rust, sludge, scale, algae and other bacteria.

The risk of legionnaires’ disease is increased if water droplets are produced and dispersed in aerosol form for example in a shower or spa bath.

It is possible to reduce the risk by removing exposure to water droplets and aerosol and by removing the nutrients on which the legionella bacteria feed.  This can be done by keeping water systems clean by cleaning and disinfecting cold water storage tanks and showerheads.


How do I comply with latest HSE guidance?

The current HSE guidance documents for the legionella control are the L8 Approved Code of Practice and the HSG274 Legionella technical guidance.


The first thing to do is a Legionella Risk Assessment, to consider the risks from legionella that may affect your staff or members of the public, and then take suitable precautions to control and prevent the risk.



Is it a legal requirement to have a legionella risk assessment?


There is a legal duty for employers and landlords to consider the risk legionella bacteria in buildings under your control or management. You must identify and assess the source of risk i.e carry out a legionella risk assessment. Manage the risk. Put in place measures to control or prevent any risks.  Keep good records to prove you are taking the appropriate action and to show to external agencies you are following the HSE guidance for legionella control.


What can be used to control legionella bacteria?

Temperature is usually used in hot and cold-water systems, by keeping hot water at above 60 degrees and ensuring it is above 50 degrees at the outlets. Cold water should be kept at below 20°c.

There are other methods which can be used if temperature is not an option, such as copper/silver ionisation and chlorine dioxide.  Cooling towers / systems are often treated with biocides.  There are other treatment strategies available such as ultra violet (UV) irradiation.


Do I need to take Legionella samples?

This depends on the risk assessment and control methods being used.  In some circumstances it will be required, however it needs to be done at a UKAS accredited laboratory and will require specialist help.  Dantek can provide advice on sample frequency and locations, and what to do if Legionella is detected.


Routine Legionella testing however is not a requirement in domestic hot and cold-water systems.  It would only be recommended in hot and cold-water systems due to exceptional circumstances where typical control measures are not working.  A full legionella risk assessment would identify the best course of action to reduce the risk.


To get an indication about whether microbial control is being achieved taking a TVC sample (total viable count) will allow the system to be monitored.  TVC samples are normally carried out for cooling towers and spa pools.  For other systems the risk assessment will identify is sampling is recommended.


Where can I get more information?

  • Order a copy of the Approved Code of Practice and guidance Legionnaires’ Disease: The control of legionella bacteria in water systems L8 here »
  • Contact the Water Management Society (WMS)
  • Check out the LCA legionella control association directory of Water Hygiene companies
  • Call Dantek for free expert advice and support about all legionella control issues


What will a legionella risk assessment cost?

The cost will depend on what assets are on your site and how many buildings.  For large sites or multi-site portfolios a site visit by one of our team is the best way to establish exactly how much a risk assessment will cost. However, we are often able to provide a guide price if you know roughly the size and type of building.  For example, how many floors, what it is used for, whether there are any cold-water storage tanks, number of calorifiers and if there are any cooling towers. An asset register of plant and equipment can be very helpful in determining how long the on-site assessment will take and therefore the cost.


One of our team would be happy to talk through on the phone any requirements and enquiries.


What do Landlords need to do about Legionella control?

The law clearly states if you are a Landlord and rent out your property then you have a duty under Health and Safety Law to consider the risk posed by Legionella bacteria. The ACoP L8 (3rd edition) also states Landlords must assess the risk from exposure to legionella to their tenants.

In most cases the risk assessment is simple and straight forward, however for more complex systems or if the Landlord is not able / competent to carry out the assessment they can use a specialist Water Treatment Company like Dantek, to carry out the legionella risk assessments and advise on any actions required.

A simple risk assessment will identify if a system is considered a low legionella risk and no further actions are required other than to review the assessment regularly in case anything changes which may affect the risk for example the water system in the building changes.

Examples of low risk systems include;

  • A small building occupied by people not considered at risk from legionella bacteria.
  • Where there is enough usage of water per day to ensure the entire system is changed at least once.
  • Mains fed cold water supplies the entire system, so there are no cold-water storage tanks.
  • Hot water is fed from combi boilers/ instantaneous heaters or low volume water heater where the hot water is supplied at no less than 50°c
  • The only outlets at the property are toilets and wash hand basins with no showers present on site.


What is meant by the term water system?

A water system includes all plant and equipment for example all the pipework, pumps, cold water storage tanks, valves, showers, water softeners, chillers, heat exchangers, cooling towers, calorifiers, little used outlets and dead legs, humidifiers, air washes, car washes, indoor fountains and water features.


How do I choose a water hygiene company?

Choosing a water hygiene company with the knowledge and skills to manage and control the risk of legionnaires’ disease at your site is made easier with the help of the Legionella Control Association.  The LCA hold a register of members who have met their requirements on an annual basis and have passed their annual audit of systems.

A key factor should be the training of site staff to carry out water hygiene work competently.  A provider will be able to demonstrate how their employees are trained and audited to ensure continual compliance with current standards.

The LCA code of conduct sets out the standard of service a client should expect from a water hygiene provider.  The code requires a Service Provider to set up an appropriate management system for the control of legionella complying with the latest HSE guidance for the control of legionella bacteria.

How many cases of Legionnaires Disease were there last year?

The figures for 2017 are not available yet however in 2016 according to a report by Public Health England, there were 359 cases of Legionellosis cases reported to the National Surveillance Scheme for Legionnaires’ disease in England and Wales.  70.4% of these cases were male and 29.6% female.  With 60% of the cases were reported in people over the age of 60.

57% of cases are thought to have been infected by the organism in the community, with 41% of cases relating to travel abroad and 2% relating to healthcare premises.  Three quarters of those who were diagnosed already had an underlying health condition making them more susceptible to legionnaires’ disease.

The HSE take the view that all these deaths were preventable as it was a man-made system which allowed the bacteria to grow and proliferate to cause an outbreak.  As such the HSE take the view that all businesses should consider the risk from Legionella bacteria and follow the AcoPL8 and HSG274 guidance on the best way to prevent and control it.


TVCC water sampling success


TVCCDantek engineer Dan Plaistow received high praise from a customer for the water sampling work he did last week.  The customer was delighted with his work and wrote “Please pass on my thanks to your engineer; Dan, who is an ambassador for your company. Polite, professional in his work ethic & very knowledgeable.”  He was tasked to take pre-flush TVCC samples and post-flush disinfection samples at numerous locations within the building on the domestic system.

All our sampling work is carried out by trained engineers, following specific method statements and using aseptic techniques to minimise the chance of sample contamination.  Any water samples taken will be tested by a UKAS accredited laboratory under certificate number 2048.

For a quote or more information please email

What are Dantek looking forward to in 2018


With the New Year underway we are excited about the prospect of some changes at Dantek, focusing on 2 key areas; skills and productivity.

As with many service based companies our people are our business and we know that to achieve our high growth target we must invest in developing high level technical skills, engagement in work, retention and the recruitment of suitably skilled new starters.

Our top priority is focusing on ensuring our workforce have the skills, confidence and knowledge to perform to the best of their ability.  To improve on our already robust mentor training programme we intend to build a practical training hub at our HQ in Thornbury.  The hub will have live water systems set up to allow engineers to be trained practically in a realistic environment, this will include higher level training in chlorine dioxide units, chemical cleaning and water softener service to name a few.

Martin Kingdon Technical Director at Dantek commented “it will be great to have a bespoke training centre (which may be the first of its kind) especially for new starters to practice in a live setting without the worry and pressure of being on a customer site.”

By investing in training and improving skills throughout the company we are confident engagement will improve and as a result productivity.  We also know the importance of recognising and rewarding our employees who all play a vital role in ensuring customers receive the best possible service. As such this year will also see the introduction of a company wide incentive scheme to allow employees to benefit from the overall success of the company.

As with many SME’s we see the greatest challenge being the ability to continually future proof the company. As such, we will continue to invest heavily in technology for example; our cloud based temperature monitoring log book system which we include for free as part of our water hygiene contracts.

Dantek Environmental Services are a Water Treatment Company, who specialise in the prevention and control of Legionnaires disease.  Founded in 2003, now based in Thornbury and employ 30 people.  Targeted to achieve £3 million turnover.

Designing out Healthcare Acquired Infections Conference

Technical Director


Technical Director Martin Kingdon is attending this conference held at the Society of Chemical Industry.  It will allow Dantek to better understand the needs of good design in healthcare buildings and water systems, to reduce the current numbers of Healthcare Acquired Infections (HAIs).

As Technical Director Martin is continuously improving the processes and advice we provide to our Healthcare customers to ensure the service offered is up to date with current guidance.  This is important as we work with many Hospitals, care homes and healthcare premises providing water treatment and water hygiene services.


New Water Treatment contract at Smart Systems

water treatment contractSmart Systems have chosen Dantek to manage the water treatment at their 30,000 sq/m site in Yatton. Smart Systems are the UK’s leading suppliers of aluminium glazing systems and bespoke aluminium extrusions.

Martin Kingdon; Techincal Director at Dantek said “we are delighted to be working with Smart’s, through our consultative approach we are already making improvements and ensuring compliance with the latest guidance.”

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