1
Filtration
The circulation pump sends the water to the filters, with recirculation times that depend on the depth and use of each area of the pool.
Swimming pools
Public and collective-use swimming pools
In type 1, 2 and 3 swimming pools, UNI 10637:2024 (Italian standard) requires automatic measurement and control of free chlorine and pH and does not allow the chlorine value to be derived from the Redox potential. The systems measure free chlorine directly in mg/l with an amperometric cell: up to 150 m³ the WDpHCl, with integrated pumps; above 150 m³ the LDpHCl, with pumps sized for the pool; for complete management of the plant, the Centurio POOL.
- Compliant with UNI 10637:2024
- Type 1, 2 and 3 pools
- Free chlorine in mg/l
- Up to 150 m³: WD · above: LD
- Multi-parameter Centurio POOL
150m³Threshold between WD and LD
0.01mg/lClosed cell resolution
0.7 – 1.5mg/lFree active chlorine in the pool
10Centurio POOL channels
How it works
The treatment circuit of a public swimming pool
The plant operates continuously, 24 hours a day: the water is filtered, analysed and disinfected in the plant room before returning to the pool.
Insight: swimming pool water →
2
Measurement
A water sample flows through the probe holder, where free chlorine and pH are measured with the resolution required for comparison with the legal values.
3
pH control
The pH is controlled automatically: the corrector is injected in solution into the circulation system, downstream of the filter.
4
Chlorine dosing
Hypochlorite is dosed only in solution into the system, never into the pool while it is open to the public, with pumps interlocked with the circulation.
5
Return to the pool
The filtered and disinfected water returns to the pool, where free chlorine and pH remain within the set values.
6
Make-up
The daily water renewal, of at least 30 litres per bather, is measured by the water meter and logged: with the Centurio POOL the volume is counted by the controller.
Typical layout
Typical layout
The treatment system is installed in the plant room, downstream of the filtration: the probes analyse a water sample and injection takes place on the delivery pipe to the pool.
UNI 10637:2024
What the standard requires
Each pool must have its own automatic system for measuring, controlling and dosing the disinfectant and must control the pH automatically.
Insight: UNI 10637:2024 in brief →Free chlorine and pH within limits
Free active chlorine between 0.7 and 1.5 mg/l, combined chlorine up to 0.4 mg/l, pH between 6.5 and 7.5, measured with a DPD photometer or an amperometric meter with a resolution of at least 0.1 mg/l.
Redox as supplementary only
Permitted for monitoring organic pollution and as a supplement to the chlorine probe; it is not permitted to derive the chlorine value from it.
Safe dosing
The dosing pumps are interlocked with the circulation, so that they do not dose when there is no flow; the tanks ensure at least 24 hours of autonomy.
Data logging
Automatic logging of the values is recommended; the daily water renewal must be measured with the water meter and recorded.
WDpHCl – up to 150 m³
Controller and two solenoid dosing pumps in a single unit, with probe holder, cell and sample filter pre-assembled on a panel: for type 2 pools up to 150 m³, such as those of hotels, campsites and residential complexes.
LDpHCl – above 150 m³
Two-channel controller with colour display and external dosing pumps, selected according to the pool volume and interlocked with the circulation; it also manages flocculant dosing.
Why the closed cell in a public swimming pool
- The legal value in mg/l: it directly indicates the free chlorine to be compared with the values of the standard, with a resolution of 0.01 mg/l: ten times finer than the minimum required.
- Many bathers: the membrane excludes the combined chlorine produced by bathers: the reading remains that of free chlorine alone, even at peak times.
- Stabiliser excluded: cyanuric acid does not reach the electrodes; pH and temperature are compensated in the cell.
- Simpler self-monitoring: calibrations kept to a minimum: the automatic measurement remains aligned with the manual checks required by the self-monitoring plan.
Quiet version with peristaltic pumps: WNpHCl.
As an alternative
Free chlorine with ECL6 open cell
The same systems with the ECL6 open cell, 0 – 10 mg/l range, also accepted by the standard as an amperometric meter.
WDpHCl with open cell – up to 150 m³
With the two pumps integrated in the controller.
LDpHCl with open cell – above 150 m³
With external pumps sized for the pool.
Limitations of the open cell in a public swimming pool
- Combined chlorine: the electrodes are in contact with the water and are affected by the presence of combined chlorine, which increases with the number of bathers.
- Stabiliser and pH: cyanuric acid affects the reading; the pH is compensated in the controller and has a lesser influence.
- Periodic calibration: the measurement must be compared periodically with the DPD photometer and the cell recalibrated more frequently than the closed cell.
Complete management
Centurio POOL: all the pool parameters
For type 1 pools and for plants with greater requirements: a single controller measures free, total and combined chlorine, pH and Redox, logs the make-up and discharged water and controls dosing, filtration, heating and lighting.
Panel-mounted Centurio POOL
Up to 10 measuring channels, touch screen, 6 timed outputs; Ethernet, Wi-Fi and Modbus as standard. The worthy successor to the MAX5.
Combined chlorine and water renewal
Two closed cells measure free and total chlorine: the controller calculates combined chlorine from the difference, to be kept within 0.4 mg/l. Two water meters measure make-up and discharge.
Completing the plant
Dechlorination of discharges and footbath
Insight: swimming pool water discharges →
Dechlorination of discharges
Backwash and drain-down water is brought within the chlorine limits set for the receiving body: constant dosing activated by a water presence sensor or dosing proportional to the volume measured by the water meter.
Footbath
A dosing pump injects the antifungal agent into the footbath supply pipe, in proportion to the volume measured by the pulse-output water meter.
Configurator
Which system for your swimming pool
The pool volume determines the controller; the desired management determines the chlorine measurement or the multi-parameter system.
Answer the questions: the recommended system appears below.
Recommended systemWDpHCl with SCL closed cell
Free chlorine measured directly in mg/l, unaffected by combined chlorine and stabiliser.
Components
WDpHCl controller
With the two integrated dosing pumps: pH corrector and hypochlorite.
The pump →
SCL closed cell
Free chlorine in mg/l, selective membrane, 0.01 mg/l resolution.
SCL cells →
pH electrode
EPHS combination electrode, 0 – 14 pH.
pH electrodes →
Probe holder and filter
Flow-through probe holder with flow sensor, 50 µm sample filter.
Probe holders →Recommended systemLDpHCl with SCL closed cell
Free chlorine measured directly in mg/l, with dosing pumps sized for the pool volume.
Components
LDpHCl controller
Two-channel controller with colour display: it controls the external pumps.
The controller →
pH corrector pump
Flow rate selected according to the pool volume, interlocked with the circulation.
V and VMS pumps →Hypochlorite pump
Dosing proportional to the measured free chlorine.
V and VMS pumps →SCL closed cell
Free chlorine in mg/l, selective membrane, 0.01 mg/l resolution.
SCL cells →pH electrode
EPHS combination electrode, 0 – 14 pH.
pH electrodes →Probe holder and filter
Flow-through probe holder with flow sensor, 50 µm sample filter.
Probe holders →Recommended systemWDpHCl with ECL6 open cell
Free chlorine in mg/l with the open cell, to be compared periodically with the DPD photometer.
Components
WDpHCl controller
With the two integrated dosing pumps: pH corrector and hypochlorite.
The pump →
ECL6 open cell
Free chlorine 0 – 10 mg/l, periodic calibration.
ECL6 cell →pH electrode
EPHS combination electrode, 0 – 14 pH.
pH electrodes →Probe holder and filter
Flow-through probe holder with flow sensor, 50 µm sample filter.
Probe holders →Recommended systemLDpHCl with ECL6 open cell
Free chlorine in mg/l with the open cell and pumps sized for the pool.
Components
LDpHCl controller
Two-channel controller with colour display: it controls the external pumps.
The controller →pH corrector pump
Flow rate selected according to the pool volume, interlocked with the circulation.
V and VMS pumps →Hypochlorite pump
Dosing proportional to the measured free chlorine.
V and VMS pumps →ECL6 open cell
Free chlorine 0 – 10 mg/l, periodic calibration.
ECL6 cell →pH electrode
EPHS combination electrode, 0 – 14 pH.
pH electrodes →Probe holder and filter
Flow-through probe holder with flow sensor, 50 µm sample filter.
Probe holders →
Recommended systemCenturio POOL
All the pool parameters: free, total and combined chlorine, pH and Redox, measured make-up and discharge, dechlorination and flocculant.
Components
Centurio POOL
Multi-parameter controller with touch screen, up to 10 measuring channels.
The Centurio POOL →Cells for free and total chlorine
Two closed cells: the controller calculates combined chlorine from the difference.
SCL cells →pH and Redox electrodes
Redox supplements the amperometric measurement as additional information.
pH electrodes →Flow-through probe holder
With flow sensor, which stops dosing when there is no circulation.
Probe holders →Dosing pumps
pH corrector, hypochlorite, flocculant and algicide.
V and VMS pumps →
Pulse-output water meters
They measure the make-up and discharged water, so that the water renewal is logged.
Water meters →Recommended systemCenturio POOL
All the pool parameters: free, total and combined chlorine, pH and Redox, measured make-up and discharge, dechlorination and flocculant, with pumps sized for the pool.
Components
Centurio POOL
Multi-parameter controller with touch screen, up to 10 measuring channels.
The Centurio POOL →Cells for free and total chlorine
Two closed cells: the controller calculates combined chlorine from the difference.
SCL cells →pH and Redox electrodes
Redox supplements the amperometric measurement as additional information.
pH electrodes →Flow-through probe holder
With flow sensor, which stops dosing when there is no circulation.
Probe holders →Dosing pumps
pH corrector, hypochlorite, flocculant and algicide.
V and VMS pumps →Pulse-output water meters
They measure the make-up and discharged water, so that the water renewal is logged.
Water meters →
pH and chlorine
pH and chlorine in a pool with many bathers
In water, hypochlorite splits into hypochlorous acid and hypochlorite ion, in proportions that depend on the pH: this is why the standard requires automatic control of both and the systems give priority to pH control.
Stable pH, effective chlorine
With a pH close to 7.2 – 7.4, hypochlorous acid prevails, the fastest and most effective form: with the same amount of chlorine dosed, disinfection is greater even at peak times.
Combined chlorine
The nitrogenous substances introduced by bathers react with chlorine and form chloramines, which cause irritation and the characteristic odour: combined chlorine must be kept within 0.4 mg/l and the Centurio POOL measures it continuously.
Dosing in solution
pH corrector and liquid sodium hypochlorite are injected in solution into the circulation system, with the corrector downstream of the filter, and never into the pool while it is open to the public.
Installation
Installation in the plant room
On panel, box or skid
The systems are supplied pre-assembled and tested, with controller, pumps, probe holder and sample filter already connected.
Injection and sample
The injection points are on the delivery line, downstream of the filtration, with an injection valve or lance; the probes analyse a sample in the flow-through probe holder.
Probe holders →Interlock with the circulation
The flow sensor of the probe holder stops dosing when there is no circulation; the controller remains powered and continues measuring in stand-by.
Chemical tanks
At least 24 hours of autonomy and containment systems; in type 1 pools the chemicals are kept in a separate, ventilated room.
Tanks →
Technical data
Technical data
Pool water requirements
| Parameter | Value |
|---|---|
| Temperature, indoor pools | 24 – 30 °C |
| Temperature, indoor pools for children | 26 – 32 °C |
| Temperature, outdoor pools | 18 – 30 °C |
| pH, chlorine disinfection | 6.5 – 7.5 |
| pH, stabilised chlorine | 6.9 – 7.7 |
| Active free chlorine | 0.7 – 1.5 mg/l |
| Active combined chlorine | up to 0.4 mg/l |
| Stabilised chlorine: free chlorine | 1.5 – 3.0 mg/l |
| Stabilised chlorine: cyanuric acid | 30 – 60 mg/l |
| Turbidity | 2.5 mg/l of SiO₂ |
| Coarse solids | absent |
Values from the State-Regions Agreement of 16 January 2003 (Annex 1, Table A2), to which UNI 10637:2024 (Italian standard) refers for pool water requirements; the requirements must be met at every point of the pool.
Insight: UNI 10637:2024 in brief →Probe data sheets
pH electrodes
| Electrode | Pressure | Connection | Body | Minimum conductivity | Junction | Temperature | Cable | Diameter | Notes |
|---|---|---|---|---|---|---|---|---|---|
| EPHS | 7 bar (3.5 bar) | BNC | Epoxy | 100 µS | – | 70 °C (80 °C) | 0.8 m | 12 mm | – |
| EPHM | 7 bar (3.5 bar) | BNC | Epoxy | 100 µS | – | 70 °C (80 °C) | 4.5 m | 12 mm | – |
| EPHL | 7 bar (3.5 bar) | BNC | Epoxy | 100 µS | – | 70 °C (80 °C) | 15 m | 12 mm | – |
| EPHSN6 | 7 bar (3.5 bar) | SN6 with PG13.5 thread | Epoxy | 100 µS | – | 70 °C (80 °C) | 1 – 100 m | 12 mm | – |
| EPHMD/100 | 7 bar | BNC | Epoxy | 100 µS | Double | 100 °C | 4.5 m | 12 mm | – |
| EPHM/D | 7 bar (3.5 bar) | BNC | Epoxy | 100 µS | Double | 70 °C (80 °C) | 4.5 m | 12 mm | – |
| EPHM/D/SN6 | 7 bar (3.5 bar) | SN6 with PG13.5 thread | Epoxy | 100 µS | Double | 70 °C (80 °C) | 1 – 100 m | 12 mm | – |
| EPHMD/LI | 7 bar (3.5 bar) | SN6 with PG13.5 thread | Epoxy | 3 µS | Double | 70 °C (80 °C) | 1 – 100 m | 12 mm | For low-conductivity water |
| EPHSC | 7 bar (3.5 bar) | BNC | Epoxy | 100 µS | Double | 70 °C (80 °C) | 4.5 m | 12 mm | Self-cleaning |
| EPHSC/SN6 | 7 bar (3.5 bar) | SN6 with PG13.5 thread | Epoxy | 100 µS | Double | 70 °C (80 °C) | 1 – 100 m | 12 mm | Self-cleaning |
| EPHM/HF | 7 bar (3.5 bar) | BNC | Epoxy | 100 µS | Double | 70 °C (80 °C) | 4.5 m | 12 mm | Resistant to 1% hydrofluoric acid |
| EPHSN6 GK | 10 bar | SN6 | Glass | 150 µS | – | −5 / 135 °C | 1 – 100 m | 12 mm | High temperature |
All models: combination electrode, range 0 – 14 pH, resolution 0.01.
Closed (membrane) amperometric cells – Free chlorine
| SCL3N/0.5 | SCL3N/2 | SCL3N/20 | SCL18/0.5 | SCL18/2 | SCL18/20 | SCL3S/20 | |
|---|---|---|---|---|---|---|---|
| Measuring range | 0 – 0.5 mg/l | 0 – 2 mg/l | 0 – 20 mg/l | 0 – 0.5 mg/l | 0 – 2 mg/l | 0 – 20 mg/l | 0 – 20 mg/l |
| Resolution | 0.001 | 0.001 | 0.01 | 0.001 | 0.001 | 0.01 | 0.01 |
| Free chlorine | Inorganic | Inorganic | Inorganic | Inorganic | Inorganic | Inorganic | Organic and inorganic |
| Water | Fresh | Fresh | Fresh | Fresh | Fresh | Fresh | Fresh or salt |
| Electrodes | 2 | 2 | 2 | 3 | 3 | 3 | 2 |
| Selective membrane | Yes | Yes | Yes | No | No | No | Yes |
| Automatic compensation | pH and temperature | pH and temperature | pH and temperature | pH and temperature | pH and temperature | pH and temperature | Temperature |
| Self-cleaning | – | – | – | Yes | Yes | Yes | – |
| Operating pH | 5 – 9.5 | 5 – 9.5 | 5 – 9.5 | 5 – 9 | 5 – 9 | 5 – 9 | 5.5 – 9.5 |
| Operating temperature | 1 – 40 °C | 1 – 40 °C | 1 – 40 °C | 5 – 70 °C | 5 – 70 °C | 5 – 70 °C | 5 – 45 °C |
| Operating pressure | 1 bar | 1 bar | 1 bar | 8 bar | 8 bar | 8 bar | 1 bar |
| Water flow | 30 l/h | 30 l/h | 30 l/h | 40 l/h | 40 l/h | 40 l/h | 30 l/h |
ECL open cells
| ECL6 | ECL6/E | ECL7 | ECL12 | ECL12/E | ECL20 | ECL21 | |
|---|---|---|---|---|---|---|---|
| Water | Fresh | Fresh | Fresh | Sea | Sea | Fresh | Sea |
| Flow stabiliser | Yes | Yes | Yes | Yes | Yes | – | – |
| Flow sensor and regulation | Yes | Yes | Yes | Yes | Yes | – | – |
| Probe holder for | Temperature, pH, Redox | Temperature | Temperature, pH, Redox (PG13.5) | Temperature, pH, Redox | Temperature | – | – |
All models: amperometric system, range 0 – 10 mg/l, resolution 0.01, organic and inorganic free chlorine, operating temperature 1 – 40 °C, pressure 0.4 – 5 bar, water flow 40 l/h.
Remote control
Remote control
Controllers and pumps can be remotely monitored and controlled via Wi-Fi, Ethernet or 4G from the web portal, free of charge and with no subscription: set points, dosing and alarms can be changed, alarm notifications received and logged data downloaded, which is also useful for the inspection log. Alternatively, integration into a PLC is via Modbus RTU or TCP/IP.
Wi-Fi
Wireless connection to the web portal, with the same functions as the cable connection.
Ethernet
Connection to the web portal via network cable: measurements, set points, dosing and alarms accessible from PC, tablet and smartphone.
4G
Connection via the cellular network for installations without a local network, with alarm notification by SMS or e-mail.
Modbus RTU
Integration into your PLC via serial port.
Modbus TCP/IP
Integration into your PLC or SCADA via Ethernet network.
The NIMBUS portal
A single account brings together all registered installations, each with its own devices: the web portal, free of charge and with no subscription, can be accessed from PC, Mac, tablet and smartphone and allows every parameter to be both viewed and changed, with an encrypted connection and protected access.
Overview
On a single screen: probe readings, chemical levels, pump activation thresholds and active alarms, with the status of installations and devices (normal, warning, alarm, standby, not connected).
Installation map
Installations appear on an interactive map with their status and open with a click; for each one, the local weather conditions and temperature are also shown.
History and charts
Archive of measurements and alarms, available for consultation at any time with charts and numerical reports exportable in Excel format.
Alarms and notifications
Alarm thresholds for readings, dosing, faulty probe and out-of-range readings, with notification by e-mail or SMS depending on the communication system; a warning is also issued when an installation remains disconnected beyond the set time.
Set points and dosing
Remote modification of the set points, of the dosing pump activation thresholds and of the corresponding hourly flow rate.
Inputs and outputs
Status of relays, pulse outputs, digital inputs and current outputs, with the name assigned to each connection.
Maintenance calendar
Tasks are scheduled by installation or by device and assigned to technicians; a reminder is sent by e-mail two days before the due date. Each task is shown as scheduled, due, overdue or completed.
Team and permissions
The main account has full access and creates the technicians’ accounts, each enabled only for the assigned installations and devices; the last login and activity of each technician are visible.
Reports and activity log
Reports on devices, tasks and technicians, downloadable in PDF or CSV with the customer’s logo; the log keeps the history of operations and disconnections.
Customisation
Logo, main colour and light or dark theme; the tiles on the main screen can be rearranged by dragging them. Two installations can be displayed side by side for comparison.
Guided registration
Each device is added through a guided procedure: the model is recognised automatically and associated with the installation, together with the technician to be contacted.
PLC integration
As an alternative to the portal, the Modbus RTU or TCP/IP port allows integration into the plant supervision system.
Installations
Installation examples
Systems are supplied pre-assembled and tested, in the form best suited to the plant room: on a panel, in a cabinet or on a skid (with cover, in a box or on a frame), also tailor-made. Some examples.
On a panel
Controller, pumps, probe holder and accessories mounted and wired on a wall panel.
In a cabinet
System panel and chemical tanks housed in a single cabinet.
Wall cabinet
Pipework, pumps and electrical panel in a wall cabinet with door.
Skid with cover
Skid with raised stainless steel frame and protective PMMA cover.
Skid in a box
Skid enclosed in a box with door, with the chemical tanks at the base.
Skid on a frame
Skid on a frame with doors, pre-assembled and ready for connection.
On the tank
Dosing pump mounted directly on the tank: the most compact solution.
In the plant room
Wall installation in the plant room, with the chemical tanks on the floor.
Pumps, controllers or components supplied by the customer can also be fitted, with custom dimensions, back panel and electrical panel. Dosing stations and skids →
Which one to choose
From the simplest to the most complete solution
For chlorine and other disinfectants the basic solution is the dosing station; to dose according to the concentration actually present in the water, measuring controllers are used.
Dosing station
The simplest solution: the pump doses at a constant rate or in proportion to the volume of water measured by the pulse-output water meter.
Details →
LDsRh
Dosing based on the Redox potential of the water: an economical solution, based on an indirect measurement.
Details →
LDsCL
The amperometric cell directly measures the disinfectant concentration in mg/l, ensuring maximum dosing accuracy.
Details →
LD Dual Parameter
Simultaneous management of two parameters, for example pH and chlorine, with a single controller.
Details → Centurio PRO
Management of up to 10 parameters and of all the pumps in the installation, with touch screen and remote control as standard.
Details →Technical consultancy
Tell us the pool volume, the type of use and the characteristics of the plant room: we will propose the most suitable system, probes and accessories.