The question
What does an analysis actually tell you that a treatment supplier cannot assume?
Treatment chosen without analysis is treatment chosen from a catalogue
The same cooling tower in two cities, fed from two different supplies, needs two different programmes. The equipment is identical; the water is not, and the water is what the chemistry has to deal with.
Without analysis there is no basis for choosing an inhibitor, no way to establish achievable cycles of concentration, no basis for a filtration degree and nothing to compare against when something later goes wrong.
The parameters that drive decisions
| Parameter | What it decides |
|---|---|
| Calcium hardness and alkalinity | Carbonate scaling tendency and achievable cycles of concentration |
| Chloride and sulphate | Corrosivity, and whether the metallurgy present is suitable |
| Silica | A hard ceiling on concentration; often the real cycles limit |
| Iron and manganese | Deposition risk and whether pretreatment is required |
| pH and conductivity | Control setpoints and inhibitor window |
| Suspended solids and turbidity | Filtration requirement and degree |
| Microbiological indicators | Biocide selection and control strategy |
The sample decides the answer
Where and when a sample is taken matters as much as the analysis performed on it. A sample from a dead leg describes the dead leg. A sample drawn immediately after a chemical slug describes the slug. A sample taken on a single good day describes a single good day.
Some parameters change between the tap and the laboratory. pH shifts as dissolved gases equilibrate. Iron oxidises on exposure to air. Microbiological samples change in transport. Where these matter, they are measured on site or the sample is preserved appropriately.
For a cooling or boiler system, both the make-up and the system water are needed. The make-up defines the starting point; the system water shows what has actually happened to it inside the plant. Either alone answers half the question.
Results are not an answer
A results sheet is data. It becomes a treatment decision only when read against the metallurgy, the operating temperatures, the cycles, the residence time and the duty of the actual system.
The same chloride figure is unremarkable in an all-carbon-steel circuit and a serious constraint where stainless steel is present at temperature. The same alkalinity is manageable at three cycles and a scaling problem at six. Context is the whole of the interpretation.
What to check
- 01Sample both the make-up and the system water for cooling and boiler systems.
- 02Take the sample from a flowing, representative point — not a dead leg or a post-injection point.
- 03Record operating conditions at the time of sampling: load, temperature, recent chemical additions.
- 04Measure the parameters that change in transit on site.
- 05Match the parameter set to the application rather than ordering a standard panel.
- 06Read the results against your metallurgy, temperatures and cycles.
- 07Keep the results — the first analysis is the baseline everything later is compared against.
When to get technical support
If the analysis and the observed system condition disagree — good results but visible deposits, or poor results but no evident damage — the sampling regime is usually the first thing to question rather than the laboratory. Where deposits or corrosion are already present, a deposit sample analysis alongside the water analysis identifies the mechanism directly, and it is worth far more than either test alone.
Talk to an EngineerFrequently asked
It depends on how stable the source is and how critical the system is. A stable supply on a non-critical system needs less frequent analysis than a variable surface source feeding a production-critical plant. What matters is that the interval is short enough to catch a change before it causes damage.