Back to Basics

Published on 04/28/2023 | by Waterline Admin

As featured in Waterline Spring 2023

Back to Basics

Matt Morse, Principal Consultant, Dragonfly Water Consultancy

In my day to day work I see a lot of audits, water treatment programmes, legionella risk assessments and written schemes of control. Many of these that I see suffer from a common problem – they start in the middle instead of at the beginning. They don’t go back to basics. Back to basics was the name of a conference the Society ran some years ago and it’s a great way to get to the root cause of problems.

It’s often said that failure to plan is planning to fail. The extent of the ‘plan’ within a lot of work I see is referring to guidance, referring to the manual. There is a reluctance or ignorance in some cases to step back, view what needs to be done and design a plan without the training wheels of guidance.

I’m going to ramble on a bit about the basics of our industry. Some of it might seem like we’ve lost our way, or that water treatment was done better in earlier years. That certainly is the case in some places, but I do tend to see the worst, or at least remember the worst of what I see. There is plenty of good, and even best practice out there so please don’t think this is a picture of where we are. This is where we want to avoid being! Don’t lose sight of the underpinning basics.

The HSE interventions programmes over the last decade have thrown up a lot of scary, and to some extent, embarrassing figures for our industry. For example, a third of cooling tower sites inspected were in material breach of the law. When the figures are examined, there are failures at multiple levels that a competent person would not, should not, have let pass. The thread of a lack of competence, runs through the R1118 report.

Despite a lot of work by the LCA over the last twenty years and other organisations such as UKAS, competence is still not as well understood as it should be. There is a legal requirement to provide information, instruction, and training to staff in the workplace so they can complete their work safely. This must be sufficient to ensure they are competent. So, what does that mean and how is it best done?

That their employees were competent is one of the most difficult things for an employer to prove in court. This becomes very difficult when looked at after the fact, after the breach, after the case, after the outbreak, after the death.

What are the basics of competence? Breaking this down, the employer needs to know what their staff need to know to do the job properly, make sure they know it, check they are competent in it and document the whole process.

For field based tasks that involve a method statement, this should detail the elements of that task. Take those elements and work out what underpinning knowledge is required. Possibly use the LCA knowledge and skills matrix to help identify what is needed. See if the operative already has that knowledge, if not train them. Record that training. Observe them doing the task, do they do it well, are they competent? Create a record of that check, maybe use the method statement itself as the basis for checking off each element of the task.

I often see a record of training without the check that the operative was competent. We’ve all seen people with a PhD that you wouldn’t let open a can of beans that was already open – training is not enough. There must be evidence of competence.

What about the competence of others? BS8580-1:2019 talks about assessing the competence of those involved in legionella control on the site you’re risk assessing. That process is sometimes poorly understood. Are there training records, tick, all good. Wrong! Back to basics; what are they supposed to be doing, are they doing it, are they doing it well? – then the conclusion is they are probably competent. If there is a training certificate for the site operative but all the results are out of spec and not reported to the defects log or the wrong conclusions drawn about the data – they clearly are not competent! Risk assessors have to make an assessment, a judgement, about this aspect of risk.

Legionella Basics
Legionella control seems to be an established ‘industry’ these days and I often see quoted ‘XYZ must be done because the guidance says it should’. Doing what guidance says has become the goal of compliance, but this is fundamentally flawed. The aim of the game is compliance with the Law. HSG274, and to some extent ACoP L8, are not compliance documents. They’re not specifications or sets of rules. There are areas where it would be impossible to ‘comply’ with some of the sections.

In most situations it’s often useful to take a problem back to root cause to find out where the problem started. That applies to legionella control, water treatment and pretty much anything else. With persistent positive legionella samples in water systems that won’t go away, the normal response is ‘we’ve done everything in the guidance’!

Legionella grows in water systems because of several well-known factors. If those factors are there and legionella is present, legionella will grow. If legionella is there, those factors are, or have been, there.

The ‘requirement’ for cold water to run below 20 degrees within two minutes and hot water to above 50 degrees within one minute is often quoted. Take that back to basics in ACoP L8 paragraph 59a it says to avoid temperatures where legionella can grow, 20-45 degrees. How many water systems avoid those temperatures in all parts, at all times? None! It is a question of degree, judgement, assessment – risk assessment. If the pipework runs though the boiler room on the way to the outlet and one minute and fifty seconds worth of flow is at 37 degrees for twenty-three hours a day, but the outlet reaches less than 20 degrees in under two minutes, is that OK?

The question of what to do with remote monitoring data is a topical one. The Society is developing guidance into what the data actually means in terms of risk and it’s a very difficult question to answer. The clear cut ‘compliance’ goalposts in the guidance mean that most systems don’t comply when you look hard enough or frequently enough.

Legionella control is summed up quite well in paragraph 59 of ACoP L8. Paraphrasing a little:
a) Avoid temperatures where legionella can grow
b) Avoid stagnation
c) Avoid materials that provide nutrients
d) Control release of water spray
e) Keep the system, and the water in it, clean
f) Use water treatment techniques
g) Maintain the system

There are not many systems out there, if any, that can comply with all of those all of the time in all areas. No spa pool, cooling tower, post-TMV pipework, or shower is going to ‘comply’ with 59a. In reality we use a combination of paragraph 59b, 59e and, for some systems, 59f. Those systems can be and normally are all operated at a low level of residual risk. This can be demonstrated with low general bacteria and negative legionella analysis results.

In the dim and distant past, I had the interesting and fairly unusual experience of a client with deep pockets and little appetite for risk for certain parts of their business. The Chairman had a grace and favour apartment within the office building and no expense was spared on keeping his water system safe. When the monthly legionella samples started to test positive the guidance was followed but the positives persisted. After multiple ineffective system clean and disinfections, we became desperate and started to replace parts of the system to try and eliminate the source of the issue. We replaced the shower head and hose, still positive. We replaced the water tank, still positive. We replaced the calorifier, still positive. We replaced all the accessible pipework, still positive. Then, with not much else left to try, we dug the inaccessible pipework out of the wall that had been there since construction in the 1960’s. Within this section of corroded, galvanised steel was fibrous jointing compound – probably hemp, that tested positive on surface swabs for legionella. Once removed the positive samples went away and did not return. The moral of this particular tale is that the first principles of control in ACoP L8 paragraph 59 are important and if there is a problem with no clear cause, one of these is going to be the culprit – you just haven’t found it yet. We had corrosion and organic material in the system that was sheltering and supporting legionella growth.

Often but not exclusively in legionella control, there is a general reluctance to go off the beaten track, and to make evidence based decisions where the guidance does not fit the situation well. In my experience designers of water systems tend to rely on design guides rather than take a step back and do a basic sense check on what they’ve designed. The result is often oversized or over specified water services and problems later in managing water quality.

The question of when a building should have its first legionella risk assessment is often asked and the answer is simple – before it’s been built. I’ve had the chance a few times to see designs on the drawing board and had the opportunity to make suggestions before something was built. On one occasion we had a meeting with the architects, and they unveiled their plans for a development of six buildings. At the centre of the development was the central water tank with six balanced compartments. Or should I say, what they intended to be six balanced compartments. My feedback was that there was no advantage to six compartments and the disadvantage was the much higher chance of stagnation in five of the six. The architect took that all on board and the design was to be updated accordingly. Six months later we arrived on site to find a six compartment tank with five of them heavily stagnant. It turned out nobody would take responsibility to sign off on the change to the design and we embarked on six years of legionella problems instead.

Risk Assessment
Basics Risk assessment basics tend to only really be thought of in the more advanced risk assessments! For systems where there is not much guidance out there, the only way to go is from first principles. From the basics. The more run of the mill hot and cold water systems or even healthcare or cooling systems seem to be assessed against the guidance, rather than against the risk. Legionella risk assessment these days seems to be a commodity to buy from the lowest bidder. Many that I see don’t even quantify the risk they’re supposed to be assessing.

The basics of legionella risk assessment have to be: contamination, amplification, transmission, exposure and susceptibility. CATES is the five letter TLA. Many risk assessments get these wrong.

One ‘premium’ risk assessment company with all the right accreditation and membership regularly states that cooling towers are a low risk of contamination as they are fed by mains water. That really shows the risk assessors lack of understanding of how cooling towers work.

Ignoring the building and water system history is another cookie cutter risk assessment failing. In a risk assessment from a hospital where there had already been one fatality from legionnaires’ disease and literally thousands of positive legionella results in the record, the risk assessment report stated that the chances of contamination were low. At this stage the reality was that the chance of legionella being in the system was 100% but there was a template to follow…

Amplification is another area where risk assessors can sometimes go astray. Just because a water system is able to meet the criteria in the guidance for ‘control’ does not mean that it won’t grow legionella.

In the not quite so distant past, I looked after a project where we kept getting persistent positive results despite the buildings ‘compliance’ with the guidance. Cold came through at the same temperature as the tank within the permitted two minutes. The hot came through within one minute. Everything was clean, everything moved at least once a week, what could possibly be wrong? We sampled back sequentially through pipework and determined that the colonisation was mainly in the riser areas rather than at the main plant. We then installed sensors and data loggers throughout the building to try and see what was causing the issue. The results were a surprise – it turned out the majority of the water in the building resided at legionella growth temperature for at least 22 of every 24 hours. This was enough to allow legionella to grow if it got into the system. Pipes were very well insulated and separated hot from cold as far as possible, but we still had an issue. The building was built to the building regulations Part L of the time and was therefore extremely well insulated and relatively airtight. There was nowhere for the heat from hot water or heating to go except into the cold water. The solution we came up with in the end was to ventilate the riser spaces and allow trapped heat to escape. This meant the cold water was able to maintain temperatures of less than twenty degrees in the riser spaces.

Table 2.1 of HSG274 part 2 now advises observing the thermometer during temperature monitoring for cold water temperatures that are slow to fall or hot water that is slow to rise. The key here is intelligent analysis of what that means. What do you expect, what is it doing, is it different?

Transmission risk – can the system make aerosol? If so, how much and how likely is this? Most water systems where the water is not fully contained all the time, can create aerosol.

Closed heating and cooling systems are often dismissed as being such a low risk, its virtually a no risk system. Exposure from these is likely to be rare in normal operation but what about when being maintained? Bleed air from a closed system and an aerosol is normally produced. Many recently installed heating system technologies such as heat pumps now run with flow and return temperatures that might not kill legionella. Safe systems of work for maintenance activity are essential.

Exposure and susceptibility are an interesting subject. Who is going to be exposed to the hazard? An outbreak a few years ago in a hospital originated from TMVs feeding TMTs in a toilet on the ground floor of the administration block. Susceptibility was thought to be a normal cross section of the public in the scheme of control as after all, this was a water system in an admin block. These toilets also happened to be on the route from reception to oncology outpatients. Can anybody see a potential problem with that?

The fundamental basics of legionella risk assessment are not that complex but seem to be beyond some template type risk assessment systems. The risk assessor needs to be capable of making judgement – making an assessment. There is an argument that there is too much guidance out there and it stops assessors having to think for themselves and make that judgement. There is also a culture of not wanting to make a decision and be responsible for it – ‘do this because the guidance says you must’. That misses the meaning of the word guidance!

Water Treatment
Basics Water treatment was a thing long before legionella became a popular US export. From the very first steam boilers that went bang, engineers were looking for ways to limit corrosion, scale and fouling. There are three topics that come up again and again in all water treatment and they are the fundamental basics.

Add biofouling or microbiological activity to the mix and you’ve got the four pillars of water treatment. Control scale, corrosion, fouling deposition and microbiological activity and you have control of water quality and a healthy system.

One thing that is often misunderstood is the interaction between these four areas and the law of unintended consequences. Push too hard in one corner and there will be problems at the others.

I’ve seen many galvanised steel cooling towers prematurely destroyed by the use of fully softened water makeup intended to control scale. Good intentions, blindly following health and safety guidance on avoiding scale, and lack of understanding of the process of white rust can lead to problems that are relatively easily avoided.

Microbiological control using a halogen like bromine or chlorine is established and well understood. The corrosive effect of using too much oxidising biocide is also reasonably well understood – pushing too hard on microbiological control with an oxidiser will lead to corrosion problems.

The use of a non-oxidising biocide alongside bromine or chlorine seems to be fashionable. These are sometimes claimed to be there to act as a biodispersant by the water treatment company. While some non-oxidisers do have an impact on biofilm, they are not generally classed as a biodispersant in the classic sense. The back to basics question to ask is this; is the other stuff going in with the oxidiser readily oxidisable? If it is, then in simple terms there is likely to be an issue when the oxidiser and oxidisable bits interact. Don’t forget, the one or two parts per million bromine reserve in the system is likely to a whole number in parts per thousand or even parts per hundred in the brominator. The system water containing the nonoxidising biocide will go through that brominator.

Sometimes the dose of a non-oxidising biocide is limited either by environmental limitations, operational constraints, or the human factor and the result is a dose below the level that will achieve an effective kill. Something is better than nothing though? Where do these nonoxidising biocides come from? Many are organic chemicals that when they degrade can provide nutrient for bacteria within the system. In closed systems it seems very common to dose a non-oxidiser without consideration to the conditions within the system. If the system water quality is alkaline some non-oxidising biocides will struggle to do much except feed the microbiological problem.

The key to successful management of water quality in any water system is balance. In swimming pools, we often still use water balance as a critical control to prevent corrosion of metals and erosion of grouting, but it seems to have fallen from favour in other water systems. Keeping the basics under control will lead to success. The four pillars of water treatment above can be applied to any water system to a greater or lesser extent. There might not be much in the way of microbiology growing in a steam boiler, but we still need to manage corrosion, scale and fouling.

Root Cause Analysis
As part of the recommendations following a case of legionnaires’ disease some time ago, the responsible person was advised to be trained in root cause analysis. They had enormous trouble finding a course that fit the bill because nobody seemed to offer it back then. The basic principles of this subject can be very useful when problems are encountered in legionella control.

The first part of this is accepting that there is an issue that requires solving. Falling back on faulty data or mindlessly defending the status quo, does not move the situation onward. ‘Positive legionella results are normal for that type of cooling system’, was one I heard a little while ago. Once they’d had their head removed from the sand they recognised the problem and we managed to get to the bottom of the issue.

Once a problem has been recognised, it must be diagnosed. What is the underlying cause? Understand and define the extent of the problem. For legionella, microbiology and water treatment problems there will be many assumptions. It’s very difficult to obtain all the data needed to understand everything. The principle is to determine what the problem is, why it has happened, and most importantly what needs to be done to prevent it happening again.

There could be a physical cause – something failed or broken in the water system, pump airlocked, tanks imbalanced, calorifier heating coil blocked, etc.

There could be a human cause – an action taken or not taken leading to the issue, cooling tower water treatment removed from a tender specification, a plumber leaving a hot water return valve closed after working on the system, not cleaning the packing in a cooling tower, etc. All of these have led to outbreaks in the past.

There may be a deeper organisational cause – a system, process or policy that has led to the problem. Nobody nominated as responsible person for legionella, nobody assigned to switch duty/standby pumps on the cooling system, etc.

Root cause analysis should look at each of these types of problem roots. When the underlying root cause has been found, it can be addressed. If the analysis does not get to the root cause, the problem is likely to reoccur because the cause has not been resolved.

Example 1; a positive legionella in a water system. Problem – there is legionella in the water system. Action – clean and disinfect system. Does this deal with the root cause?

Example 2; hot water is reported as running cool. Problem – water is not hot enough at taps. Action – flush hot water till it runs hot. Does this deal with the root cause?

There are several ways of getting at root cause. The two examples above are flawed because they address symptoms rather than causes. The statement of the problem misses the underlying reasons. One way to get at root cause is to keep asking why, like a toddler, until you get to the root of the problem, or get put on the naughty step. Known as the five whys because five questions are normally enough. Applied to the first problem example 1.

Q1. There is legionella in the water? Why?

Q2. Conditions in the system for legionella to grow and legionella has entered the system. Why? What are those conditions?

Q3. One compartment of the tank is stagnant and residing at 30oC. Why?

Q4. The tank is imbalanced and is gaining heat. Why?

Q5. The tank room is unventilated and at the top of the building and water resides for long enough to get warm.

The root cause at question 5 gives the answer. Don’t lose sight of the symptom – clean and disinfect that water system because there is clearly an immediate issue that needs to be dealt with. Make sure there is a recommendation to rebalance the tank, maybe reduce storage capacity, ventilate the tank room – address the underlying root cause.

Another way to try to find root cause of an issue is an Ishikawa cause and effect analysis. This looks at all the possible causes that might lead to the observed effect. This can be useful where there are multiple possible causes contributing to the observed effect. Named after Professor Kaoru Ishikawa but also sometimes known as a fishbone diagram after the shape it can make on paper.

The effect – i.e. the observed problem sits at the head of the fish. Each rib line coming off the spine is a different possible cause or contributary factor. Some of the ribs might have contributary ribs of their own. The contributory factors are often classified into those related to people, equipment, methods and materials.

For our example 2 the analysis might look something like this:

We can unpick each strand of the problem and its possible contributory factors. For each of the branches there could be:

• People factors (did somebody leave a valve closed they shouldn’t have, has somebody turned off the calorifier?)

• Equipment factors (has the calorifier heat source or recirc pump failed?)

• Method factors

• Materials factors (was this system designed with long runs of noncirculating hot water?)

For this real example the issue was an unbalanced hot water system. Lockshield valves were closed in some areas and changes in the system layout meant that areas of the system had lost balance, were not circulating and hot water in the pipework was cooling down over time. Flushing for five minutes brought hot water through but did not solve the underlying stagnation and legionella growth issue. As a result of the root cause analysis, the action taken was to rebalance the hot water system. This meant that all the circulating parts circulated as they were supposed to and water at outlets was hot within seconds.

All of the above is an attempt to describe the underlying basics. The first principles of control, principles of identifying and quantifying risk, basic fundamentals of water treatment and the root causes of problems.

Using downstream guidance, without heeding the basics sometimes leads us astray. Where the guidance comes to an end, all we have are first principles and we must think for ourselves.

Diary Dates & Events

Grime Scene


Following on from the successful Grime Scene competition, we have decided to continue the theme for another year, but with a twist. This year, we are asking for photographs of the grimiest pictures you can find accompanied with another photograph of how the ‘scene’ has been improved by your maintenance or cleaning.

We will display the photographs in each of the Waterline editions throughout 2024. The ‘most improved’ picture will be chosen by WMSoc members via an online vote. The winner will receive a £25 Amazon Gift Voucher after the Winter 2024/25 edition has been published.

Please send your photographs to:
[email protected].

Product & Service Spotlight

Introducing B & V Chemicals' Multitreat SHD showerhead descalers.

Multitreat SHD showerhead descalers from B & V Chemicals are easy to use and effectively eliminate Legionella spp and Pseudomonas aeruginosa.

Independent tests confirm its efficacy, achieving a 5 log reduction within 5 minutes. Proven to prevent Legionella growth, Multitreat SHD ensures peace of mind by addressing scale buildup quickly.

Customer feedback and laboratory tests validate its reliability.

For more information, contact [email protected]

How the NEW SolidTek® Biocide Feeder Package will BENEFIT YOU

SolidTek® has launched its NEW Biocide Feeder which is functional, compact, and environmentally-friendly.

Designed for use with SolidTek’s® enhanced bromine biocide, BromTek, it offers multiple benefits:

Reduced exposure to fumes and bromine dust (non-pressurised system).

Use with field proven mixed hydantoin biocide - better performance than standard bromine tablets.

Wall mounted reducing footprint of installation.

Charge with product in under 5 minutes without isolation from the system.

Product calculators and tech support available.

Lovibond MD640 Photometer (PTSA & Fluorescein capable)

Product Spotlight Drop Test Kits

How many times have you heard … ‘we’re not sure what the system volume is’. A common problem which can be expensive - wasting chemical over dosing, or underdosing so the treatment is ineffective (i.e. shock dosing a biocide). The MD640 photometer has PTSA & Fluorescein capability built in. Simply use our System Checkers to add to an unknown system and read a PTSA or Fluorescein levels to accurately identify the system volume.

The Hydrosense PRO range


The Hydrosense PRO range pioneers Legionella pneumophila detection, the cause of over 97% of Legionnaires’ disease outbreaks, by identifying all the serogroups 1-15 of this dangerous Legionella species. This easy-to-use, highly sensitive test uses unique filtration, offering a three-line test result that distinguishes between serogroup 1 and serogroups 2-15 within 25 minutes. The water test has a level of detection of 100 CFU/L and swab tests detect 200 CFU per swabbed area, providing crucial, rapid insights for water safety management.