If you intend to be the future owner of a swimming pool or if you are already a well -established company that builds swimming pools, you should know that it is necessary to maintain cleanliness and sanitation of water.
The chlorine level is measured based on the ORP or REDOX principle. An increase of the ORP value correlates with an increase of the free chlorine level.
pH and disinfectant testings are made together for more efficient disinfection and control. The efficacy of sanitizers, is dependent on a controlled pH value. The ORP value is the most consistent indicator of the sanitizing effectiveness of the pool/hot tub or water treatment.
Typically 650-750 mV at 7.2 pH indicates proper water treatment
(all harmful bacteria are killed in matter of seconds).
The chemical reaction that is essential for water sanitation is oxidation. During the oxidation process in pool water, an electron exchange occurs between chlorine (or some other oxidant) and a contaminant in the water. In this way the contaminant is inactivated and chemically inert.
ORP is the measure of water cleanliness and its ability to break down contaminants.
ORP as parameter is measured in swimming pool water and drinking water (chlorine is used to sanitize drinking water) and it tells us how effective chlorine or some other oxidizers are in the water.
For measuring ORP we use ORP probes that detects voltage between electrodes and gives us a value whose unit of measurement is milivolts (mV). Oxidizers will show positive mV charge, while contaminants will show negative mV charge. Various ORP controllers or testers can help us in determining the quantity of an oxidizer that is beeing used for sanitation of water.
A drop in the ORP indicates an increase in chlorine demand caused by reducing agents or contaminants entering the water. A decrease in ORP indicates that chemical reactions are about to occur. Compared to amperometric control, ORP is considered to be a more accurate measure of disinfection rate.
What are the factors that effect ORP?
Various water parameters and factors can affect the ORP. These are some of the most common.
Since the form of chlorine present is pH-dependent, the pH should be balanced at an appropriate level to maximize sanitizer effectiveness and ensure swimmer comfort. Ideal pH levels are typically between 7.2 and 7.6; pH levels above this greatly reduce the effectiveness of chlorine sanitizers, and pH levels below this can cause skin and eye irritation.
Depending on the pH level, chlorine will be present as hypochlorous acid (HOCl), the most effective form for sanitization, or as the less effective hypochlorite ion (OCl¯). Chlorine will be present in greater concentrations as hypochlorous acid below pH 7.6; above this pH, hypochlorite is favored. Chlorine can also combine with other molecules present in the water; when it combines with ammonia, chloramines are formed, which are virtually ineffective at sanitizing and responsible for producing the familiar and unpleasant “chlorine” odor.
Chlorine concentration can be measured as either free chlorine residual (chlorine available for active disinfection) or total chlorine (combined chlorine that is no longer available for disinfection, in addition to free chlorine). Both are measured by DPD method, standard colorimetric method, where there is characteristic magenta color change. Intensity of color is directly proportional to the chlorine concentration.
Chlorine will break down when exposed to UV light. To stabilize chlorine in the presence of UV light, cyanuric acid may be added to outdoor pools. However, high cyanuric acid levels can also lower the sanitation power of chlorine.
Microorganisms grow more rapidly at higher temperatures, so the required sanitization level for a swimming pool or spa is highly dependent on the water temperature; this is especially concerning for heated pools and spas. A general rule of thumb is that for every 5.5°C or 10°F increase in water temperature over 27°C (80°F), the concentration of required sanitizer is doubled.
To measure ORP value, Hanna Instruments have various devices that can help you in sanitation of pool water. From automated process controllers, to simple hand testers, ensure carefree swimming and pool fun with Hanna Instruments.
For measuring on the spot we can recommend a wide range of portable meters!
HI981954
Pool Line Multiparameter Waterproof Portable
pH/ORP/EC/Temperature meter
HI981954 is made for measuring key water quality parameters in swimming pool, hot tub, or spa water. This is an advanced meter uses a single weighted probe with multiple sensors to measure multiple parameters simultaneously and display results as:
- pH
- pH in mV
- ORP
- conductivity (EC)
- total dissolved solids (TDS)
- salinity
- temperature
The meter has a built-in pressure transducer for barometric pressure readings.
- One probe with field replaceable pH/ORP, EC and temperature sensors
- Auto-ranging for EC and TDS readings
- Display up to 11 measurements simultaneously
HI981914
Professional Waterproof Portable pH/ORP/ISE Meter
HI981914 is made for measuring pH and ORP of a swimming pool, hot tub, or spa water. This is an advanced meter with many features including Han-na’s exclusive CAL Check pH electrode diagnostics that is used to iden-tify potential problems including when to clean the electrode, check a buffer for contamination and the overall health of a pH electrode. This function can be used to identify issues with process probes that have a BNC connector.
- Laboratory grade measurements in a portable
- CAL Check advanced probe diagnostics
- Troubleshooting tool for the maintenance of process probes
Pool Line testers – specialized line of testers designed with pool pa-rameters in mind!
HI981204
ORP/Temperature
Pool Line Tester
Pool Line Tester
HI981204 Pool Line ORP and temperature meter is made for measuring the oxidation (chlorine) level of swimming pool, hot tub, or spa water. This lightweight, waterproof tester offers high accuracy ORP, and temperature measurements in a single handheld unit.
- Waterproof
- Replaceable ORP electrode
- Simultaneous display of ORP & temperature
HI981214
pH/ORP/Temperature
Pool Line Combo Tester
Pool Line Combo Tester
pH/ORP meter is made for measuring pH and ORP of a swimming pool, hot tub, or spa water. This lightweight, waterproof tester offers high accuracy pH, ORP, and temperature measurements in a single handheld unit.
No more switching between meters for your routine measurements!
- Waterproof
- Replaceable pH electrode
- Automatic calibration
The easiest way to achieve clean and clear water in the pool is with automatic dosing of chemicals.
BL12X pumps measure and precisely control chlorine and pH balance with the help of integrated peristaltic pumps and multiparameter pH/ORP/Temp probe.
This gives a complete compact system that can measure, analyze and make automatic dosing based on the parameters that are measured (pH/ORP). This way the water quality is continuously monitored and precise dosing of chemical is enabled.
BL122 • BL123
pH/ORP Controllers
with Cloud Connectivity
BL122 and BL123 are designed to maintain constant pH and disinfectant levels in swimming pools, hot tubs, and spas and offer the added benefit of allowing remote
connection and access to devices via the Hanna Cloud web app. These controllers are available in two configurations. The basic version is the inline model which allows for direct installation of probe and chemical injection fittings into existing piping. A panel mounted version with a bypass flow cell is also available. The bypass flow cell allows for calibration and maintenance of the probe without having to shut down the recirculation pump.
BL120 • BL121
pH/ORP Controllers
with Built-In Chemical Feed Pumps
These Swimming Pool Controllers are a complete system designed for maintaining
swimming pool, hot tub, and spa disinfection water quality. These controllers are available in two configurations. The basic version is the in-line model which allows for direct installation of probe and chemical injection fittings into existing piping. A panel mounted version with a bypass flow cell is also available. The bypass flow cell allows for calibration and maintenance of the probe without having to shut down the recirculation pump.
BL101
Pool Line ORP Controller and Dosing Pump
Engineered to be an inexpensive solution for homeowner and maintenance companies to maintain the ideal ORP at all times of a swimming pool or hot tub. The BL101 Pool Line ORP Controller and Dosing Pump is a complete solution with both a process controller and a chemical dosing pump. Simply insert the probe and injection valve in-line with the re-circulation pump and supply the oxidizer (i.e. chlorine) to be dosed.
- All in one solution for maintaining the proper ORP value
- Industrial process probe with 1/2″ NPT threads for insertion into re-circulation line
- Input for level controller or flow switch
PCA300 Series
Chlorine, pH, ORP, and Temperature Analyzers
The Hanna Instruments PCA310, PCA320, PCA330 and PCA340 series of chlorine, pH, ORP and temperature analyzers are microprocessor controlled, process analyzers which continuously monitor a sample stream for chlorine content, pH, ORP and temperature values. The PCA Analysers uses DPD Colorimetric method for determining chlorine.
- 4 models available for monitoring chlorine, pH, and ORP levels
- Two separate selectable 0-20 or 4-20 mA signal output (PCA340 only)
- User-friendly interface simplifies setup and maintenance
Author:
Nives Vinceković Budor
mag.ing.chem.ing.
Nives Vinceković Budor
mag.ing.chem.ing.
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