When did anyone last check the water in your heating and chilled water circuits? If the answer is "at handover", the system may already be corroding from the inside.
Water Hygiene Services is an independent water hygiene company based in Leeds, and we are testers first. We take samples from closed heating, chilled water and heat pump systems, have them analysed by a laboratory and give an independent review of the results, to BG 29 for new systems and BG 50 for running ones, to estates managers, facilities managers and building and property managers, with sampling to BS 8552.
We report on your results independently. We take the samples, send them to an independent laboratory rather than analysing them ourselves, and report what the results show, separate from the contractor who treats or commissioned the system.
We work in Leeds and West Yorkshire, Hull and Humberside, Manchester and Greater Manchester, Newcastle and the North East, Nottingham and the East Midlands, and Sheffield and South Yorkshire.
Get a written quote for closed system testing
What is closed system water testing?
A closed system is a sealed circuit of water that is heated or cooled and pumped round a building without being used for drinking or washing: low temperature hot water heating, chilled water, heat pump and condenser water circuits, and community heating networks. The water stays in the pipework, so it is easy to forget it. It still needs looking after.
Closed system water testing is the routine sampling and analysis that shows whether the water treatment in that circuit is working. Left unchecked, the water can corrode the pipework, drop solids into pumps, valves and terminal units, and grow bacteria that attack metal from inside. Those problems cost energy, shorten the life of plant and can end in a failed heat exchanger or a leaking radiator.
We take the samples, send them to a laboratory for analysis, and review the results for you, independently, in plain language, with the action each one needs.
- Heating, chilled water, heat pump and condenser water circuits
- Fan coil units, chilled beams, radiators, plate heat exchangers and air handling unit coils
- New systems after pre-commission cleaning and before handover
- Existing systems on a routine monitoring programme
- Systems after repairs, additions or a drain-down
- Systems where a treatment contractor has made a change and you want a second view
BG 29, BG 50 and BS 8552: what each one covers
Three documents are used together for closed systems, and facilities managers often hear all three named in one conversation.
- BSRIA BG 29 covers pre-commission cleaning of pipework systems: flushing, cleaning and the water quality results expected before a new or altered system is handed over.
- BSRIA BG 50 covers water treatment for closed heating and cooling systems: how corrosion, scale, sediment and biofouling are controlled once the system is running, and how the treatment programme is managed and monitored.
- BS 8552 is the code of practice for sampling and monitoring water from closed building services systems. It sets out where and how samples are taken, handled and transported.
- BG 29 gets the system clean at handover. BG 50 keeps it that way. Sampling to BS 8552 is the evidence that it has happened.
Testing panels: what we test for
We use two levels of testing, chosen to match the system and the treatment product in use. We report against the BG 50 guideline values, and against the control limits your treatment provider sets, where they differ.
The routine panel is the everyday check on a running system. It looks at:
- Appearance, noted at the point of sampling
- pH
- Conductivity and total dissolved solids
- Iron, to show whether metal is being lost
- The level of the corrosion inhibitor (molybdate)
The fuller diagnostic panel
The fuller panel includes everything in the routine panel and adds more detail, so the cause of a problem can be understood before any remedial work is planned. It adds:
- Suspended solids
- Total hardness and total alkalinity
- Chloride
- Dissolved iron, as well as total iron
- Copper and aluminium
- Nitrite
- Glycol percentage, for chilled systems that use glycol
- Bacteria tests: nitrite-reducing bacteria, pseudomonads, sulfate-reducing bacteria and total viable count
Which panel is used, and when?
The routine panel is used for a first check on a system, for regular monitoring and for following the trend against earlier results. The fuller panel is used when a routine result points to a problem, for an annual deep-dive on a known problem system, and to check the system before and after remedial work. It is also used where a full diagnostic is wanted.
Chemistry results are usually back within one to two weeks. Bacteria testing takes longer, because some of the organisms we test for, including sulfate-reducing bacteria, need a long incubation period before a result can be given, so allow up to about three weeks for the bacteria results. If you need the chemistry results first, we can report on them separately and follow up with the bacteria results when they arrive.
What your report looks like
Every result comes back in a clear written report, not a bare table of figures. Each report follows the same structure, so it is easy to compare from one visit to the next.
- Site and system details, and when and where the sample was taken
- A summary of the findings in plain English
- The results, each rated Pass, Advisory or Fail against the benchmark
- What the results suggest about the condition of the system
- Recommended actions, in priority order
- The trend against any earlier samples, so you can see whether things are improving, stable or drifting
When should a closed system be sampled?
There is no single answer for every building, because the right programme depends on the size of the system, how it is used and how much it changes. BG 50 gives a typical routine frequency, for heating and cooling systems in non-domestic buildings in mid-life, of between one and three months. More frequent sampling is recommended during the first six months of a new system, and after any significant change such as replaced or added plant or terminal units.
- At handover, to show the system meets the clean-water guidelines in BG 29
- Every one to three months in mid-life, as the programme requires
- More often in the first six months of a new system
- After repairs, additions, a leak or a drain-down
- When inhibitor levels fall or the water looks wrong
- Before and after a flush, or a treatment change
Newly commissioned building? Verify the sign-off independently
A building has been built, the system has been commissioned and the contractor has signed it off. Has anyone independent checked the water? BG 29 sets the water quality expected before a new or altered closed system is handed over, and it is the builder or the commissioning contractor who normally reports against it.
BG 29 also covers the pre-commission cleaning of the pipework. Sampling the water before and after cleaning and flushing gives written evidence that the system has been cleaned to a suitable standard before treatment starts and before the building is handed over, and we can carry out that sampling independently of the contractor who did the cleaning.
We can be the independent party. We test the system against BG 29 using our own sampling and testing regime, and report whether the results support the sign-off. You get evidence that is separate from the contractor who did the work, which is what many clients, funders and facilities teams want before they accept a building.
- New build and refurbishment projects before or just after handover
- Clients, developers and landlords who want a check separate from the contractor
- Facilities teams taking over a building and wanting a clean starting record
- Follow-up sampling in the first months of operation, when BG 50 recommends more frequent checks
Want a second opinion on your current water treatment provider?
Your treatment provider looks after the programme and reports on it. An independent test gives you a second view. The sample is taken by us, analysed by a laboratory, and reviewed against BG 50 guideline values, with no link to the product being dosed.
Many clients use it as a periodic check on a running system, when they change provider, or when a result from the current provider looks wrong.
If the results show a problem and you would like help putting it right, remedial works, dosing and chemical treatment are available afterwards if you ask.
- A second view on a running system, to BG 50
- A baseline before a new treatment programme starts
- Checking that inhibitor levels and corrosion results match what you have been told
- Records that support a warranty or insurance claim on plant
What problems does sampling pick up?
Most closed systems fail slowly. Sampling shows the early signs.
- Falling inhibitor levels, from leaks, top-ups or a drain-down
- Rising iron, or copper where it is tested, showing metal is corroding
- High suspended or settled solids, which block strainers and heat exchangers
- Sulfate-reducing bacteria, which are linked to corrosion under deposits
- A strong sulphurous or ammoniacal smell
- pH outside the range for the metals in the system
Why is my iron going up when the system is dosed?
Rising iron in a closed system is not always a sign that the treatment is failing. Where inhibitor levels look healthy but iron keeps climbing from one sample to the next, the cause is often fresh water entering the system. A small leak, or an automatic pressurisation unit topping the system up when it should not, brings in new oxygen and dilutes the inhibitor, so corrosion carries on even though the dose looked right.
It works much like a combi boiler that keeps needing its pressure topped up: the problem is not the water already in the system, it is where the water is going and what is replacing it. Looking at several samples over time, rather than one in isolation, is what shows this. If we see the pattern, we say so in the report and recommend checking for water loss and the make-up arrangements, before anyone assumes more chemical is the answer.
Too much inhibitor can be a problem as well. Levels that are too low leave the system exposed to corrosion, but levels well above the recommended range can also cause problems and waste chemical. Testing shows where you actually are, so the dosing can be corrected in either direction.
Heat pump and mixed-metal systems
Air source heat pump circuits and other modern systems often contain aluminium alongside steel and copper, and many contain glycol. This matters because aluminium is sensitive to high pH, and some inhibitors that suit a steel system are not suitable for aluminium. A glycol mix also needs checking at the right strength for the system.
The fuller panel includes aluminium, copper, pH, nitrite and glycol, so the results show whether the water chemistry suits the metals actually in your system. If you are not sure what is in your system, tell us when you get in touch and we will advise which panel to choose.
What helps us before the visit
None of this is essential to get a quote, but the more we know, the more precisely the report can interpret the results. It helps if you can tell us:
- The approximate system volume, and whether it is heating, chilled or a heat pump circuit
- Whether the system contains glycol, and the aluminium content if known
- Who currently treats the system, and the date of the last dose or treatment
- Where the make-up water comes from, and whether there is a water meter
- Where the sample points are, and that we will have safe access to them on the day
- Any known problems, such as cold spots, noisy pumps, blocked strainers or frequent top-ups
How does this fit with Legionella control?
Our Legionella pages cover domestic hot and cold water, to HSG274 and ACoP L8. Closed circuits follow BSRIA guidance instead. Many buildings have both, and we can keep the two sets of records side by side, so one visit programme and one reporting format covers the whole site.
Who is closed system testing for?
We work with estates managers, facilities managers and building and property managers.
- Schools and academy trusts: independent checks on heating and chilled circuits, with clear reports for governors and estates teams
- Multi-site estates and portfolios: one consistent report format across your sites, so results can be compared
- Facilities managers and consultants: an independent view on whether a contractor's treatment is working, supported by trend reporting
- Newly commissioned buildings: independent verification that the system was cleaned and treated properly before handover
How a closed system sampling visit works
- We review your system: its type, volume, materials and age, and agree the sample points and the panel of tests.
- We circulate the system before sampling. Water that has been standing does not give a true result.
- Samples are taken at the main plant and at remote points such as low-flow pipework and terminal units, from the circulating water and the make-up water.
- Sample points are disinfected before microbiological samples are taken. Laboratory bottles are used, labelled, and sent with a chain of custody record.
- The laboratory analyses the samples. We review the results against BG 50 guideline values and the limits for your treatment programme.
- You receive a clear independent report. Anything outside the limits comes with a recommended action, in priority order, such as investigation, flushing or further sampling.
- Results go into your water treatment logbook, so you have a complete record for audits, warranty claims and handover.
Get a written quote for closed system testing
Questions facilities managers ask about closed system testing
Does BG 29 or BG 50 have to be followed?
They are BSRIA good practice guides, not law, but they are the standard that specifiers, commissioning engineers and treatment contractors work to, and they are what a client or consultant will expect to see met. A water treatment programme that follows them is easy to defend.
What is the difference between BG 29 and BG 50?
BG 29 is about getting a new or altered system clean before handover. BG 50 is about keeping the water in a running system in good condition. Sampling to BS 8552 is the evidence for both.
We already have a water treatment contractor. Why add independent testing?
Your contractor runs the programme. An independent sample gives you a result that is not tied to the product dosed. Many clients use it as a periodic check, or at handover and contractor change.
How often should we sample?
It depends on the system. BG 50 gives a typical routine frequency of one to three months in mid-life, with more frequent sampling for the first six months of a new system and after significant changes. We agree the frequency with you when we review the system.
Is the testing independent? Can you also help if there is a problem?
The testing is independent: we sample, have the samples analysed, review the results against BG 29 for new systems and BG 50 for running ones, and report what they show. If the results show a problem and you would like help resolving it, remedial works, dosing and chemical treatment are available afterwards if you ask.
What does the report look like?
For each system you get the results, whether each one is within the guideline, a plain-language comment, and a short list of recommended actions in priority order, with the most urgent first. The routine panel covers appearance, pH, conductivity, total dissolved solids, iron and the inhibitor. The fuller diagnostic panel adds more chemistry and the bacteria tests, to give a fuller picture of the system.
How long do the results take?
Chemistry results are usually back within one to two weeks. Bacteria testing takes longer, so allow up to about three weeks for those results. If you need the chemistry first, we can report on it separately and follow up with the bacteria results when they arrive.
Why is my iron going up when the system is dosed?
Often it is fresh water entering the system, from a small leak or an automatic top-up, which brings in oxygen and dilutes the inhibitor. Looking at several samples over time shows the pattern, and we will say so in the report before anyone assumes more chemical is the answer.
Can too much inhibitor be a problem?
Yes. Levels that are too low leave the system exposed to corrosion, but levels well above the recommended range can also cause problems and waste chemical. Testing shows where you are, so the dosing can be corrected in either direction.
Does closed system testing replace Legionella monitoring?
No. They cover different systems. Closed circuits follow BG 50. Domestic hot and cold water follows HSG274. We can run both for the same building.
Related services
- Legionella testing and water sampling
- Legionella monitoring
- Legionella risk assessments
- Water tank cleaning and disinfection
- Closed system water treatment, Closed Systems website
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Very happy with their very high standard of work Water Hygiene Services have been carrying out legionella risk assessments for us for a couple of years now. We have been very happy with their very high standard of work, their ability to work to tight deadlines and the general professional service they provide
