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Pool water records and testing

The part of the service nobody sees — until the day somebody asks for the file.

What we measure and what goes in writing

At every visit to a pool under contract we measure pH, free chlorine and combined chlorine, and check the state of the filtration; depending on the installation and the season we also measure total alkalinity, calcium hardness, cyanuric acid and temperature. Every value, every product applied and every job done goes into a written, dated record handed to the client. In a condominium the record is addressed to the board; in a holiday rental or hotel it builds the installation file. It is the document that answers "can you show what was done?".

Content reviewed in August 2026.

This page matters to you if you

Have to keep testing records for a pool in public use
Administer a condominium and need to account for maintenance to the owners
Run a holiday rental or hotel and want the file organised before you need it
Are comparing maintenance proposals and want to know what each one hands over in writing
Are about to sell or value a property with a pool

Why the record is the part that matters

Everyone who maintains pools says they treat the water. Far fewer can show what they measured, when, and what they did next. The difference between the two only becomes visible at three moments: when an owner disputes the cost, when a guest complains, and when somebody — an insurer, an inspector, a buyer — asks for the proof. At those three moments, a clean pool without a record is worth far less than a clean pool with one.

There is also a technical reason, and it is the one that matters day to day. A single value tells you nothing; a series tells you everything. If the pH climbs half a point a week there is a cause — hard fill water, dosing out of calibration, or a reaction from the lining — and that cause is only visible in the history. Without records, every visit starts from zero and treats symptoms. With records, you treat the source.

That is why the record is not paperwork bolted onto the service: it is the technician's working instrument and the client's proof at the same time. It costs the time it takes to write and it solves two problems at once.

What we measure, and why

The ranges below are the working ranges we use on chlorine-treated pools. They are not legal values: on a pool in public use, the local health authority or municipal regulations may set tighter ranges, and the plan is adjusted to whatever applies to your installation.

Parameter	Working range and why we measure it
pH	7.2 to 7.6, ideally 7.2 to 7.4. Outside that range the disinfectant loses effectiveness, the water stings eyes, and lining and equipment suffer. It is always the first thing to correct — treating before fixing the pH wastes product.
Free chlorine	1 to 3 mg/L in a residential pool; on a pool in intensive use we work in the upper third, because bather load consumes disinfectant far faster. Below 1 mg/L, algae start to develop.
Combined chlorine (chloramines)	As low as possible, and watched closely above 0.5 mg/L. This is chlorine already spent reacting with organic matter, and it — not free chlorine — is what causes the strong smell and stinging eyes. In an indoor pool it is also the main driver of poor air quality.
Total alkalinity	80 to 120 mg/L. It acts as the pH's brake: low alkalinity makes the pH swing with every correction, high alkalinity makes the pH impossible to bring down. It explains most cases of "the pH will not hold".
Calcium hardness	200 to 400 mg/L. Relevant in hard-water areas, and decisive in preventing limescale on walls, in the filter and in heat exchangers. Measured less often, but essential in several parts of the region.
Cyanuric acid	20 to 50 mg/L in outdoor pools on stabilised chlorine, and never above 75 mg/L. It shields chlorine from sunlight, but in excess it locks it: the water holds chlorine that does not disinfect. It is the classic cause of a pool that "has chlorine" and still goes green.
Filter pressure and flow	Compared against the clean-filter reference. A steady rise means a backwash is due; a rise that does not come back down after backwashing means sand at the end of its life or an obstruction.
Appearance, temperature and level	Clarity, colour, state of the waterline and surface, temperature and level. They do not replace the numbers, but they put them in context — and it is where a problem is spotted before it shows up in the values.

Free water-testing log template

One A4 sheet to print and pin up in the plant room: columns, reference ranges and how to fill it in. No sign-up, no email.

View and print

What the law requires of pools in public use

Which statute applies to each kind of installation, the testing and analysis cadence, the Annex II values and what the maintenance company covers — with the sources cited.

See the legal obligations

What one line of the record contains

This is the format of the record we hand over. If you are comparing maintenance proposals, it is a useful list: ask each provider how many of these fields they give you in writing.

Field	What gets written
Date and time	Day and time of the visit, and the technician who carried it out.
Values measured	pH, free chlorine and combined chlorine always; the remaining parameters according to the installation and the season.
Products applied	Product and quantity, per parameter corrected. Not "treatment carried out".
Work done	Vacuuming, brushing, waterline cleaning, basket cleaning, backwashing, equipment checks.
Equipment condition	Filter pressure, pump operation, state of the automatic doser where one is fitted.
Faults and recommendation	Anything found, with the proposed correction and how urgent it is. In writing, even when it was already said on the phone.
Expected use	On professional pools, the occupancy expected over the following days — it is what determines the dosing left behind.

The complete installation file

Over the course of a contract, this is what accumulates. It is what you hand to an insurer, an inspector, an incoming condominium board or a buyer.

Pool technical sheet: volume, lining, pump, filter, flow rate and turnover time
A record of every visit, with values measured and work done
The history of each parameter over time — the series, not the isolated value
A condition report at the start and end of each season
Written notifications of faults and the corrections that followed
A plan of foreseeable replacements, with estimated dates
A written daily measurement procedure, where the installation requires one

Records are included in the contract

We do not charge for the record separately, and be wary of anyone offering it as a paid option: a provider who measures without writing is measuring for themselves, not for the client. Every maintenance contract — from €180/month with a fortnightly visit and from €280/month with a weekly visit, VAT included — includes the written record of every visit. The technical visit to the installation produces the file's first document: the installation's technical sheet and our opinion on its capacity.

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Services this contract includes

Water Treatment Problem Diagnosis

Frequently asked questions about records and testing

The questions operators ask us before signing. If yours is not here, call us.

At every visit: pH, free chlorine and combined chlorine, plus a check on the state of the filtration. Less often, but indispensable: total alkalinity, calcium hardness and cyanuric acid. On a pool in public use, the parameters and frequencies may be set locally and should be confirmed with the health authority and the municipality.

It depends on bather load more than on volume. In a family pool, once or twice a week. In a holiday-rental pool in high season, weekly as a minimum, with a check between stays. On a pool in public use, every day it is open, which is organised by combining technical visits with daily measurement by the local team.

No. They are different and complementary. On-site measurement gives the operating values and allows immediate correction; laboratory analysis verifies parameters that cannot be measured poolside, with a report issued by a third party. On public-use installations, periodic laboratory analysis is normally expected on top of the on-site measurements.

The practical test: at least as long as a complaint or a claim relating to that season could still arise. When in doubt, keep them longer — records take no space, and their absence is always read against the operator.

It serves the one purpose that matters: showing that the installation was being maintained. The question an insurer asks is whether there was negligence, and a dated record with measurements and interventions is the difference between an accident and an allegation of negligence.

Yes. The record is handed over in a form you can file and forward — what matters is that it stays with you, dated and complete, and not only in our systems.

Three questions settle the comparison. First: do you issue a written record of every visit, and what does it contain? Second: are chemicals and testing included in the monthly figure or invoiced separately? Third: how many visits a month, and on which day of the week? A proposal that does not answer those three is not comparable with one that does.

Past history cannot be invented — if there is no record, there is no record. What we do is start the file at the diagnosis, with the installation's technical sheet and the initial condition documented in writing. From there, every visit adds a line. After one season there is enough of a series to treat causes rather than symptoms.