Importance of pH on effectiveness of chlorine disinfection

Category: Pools | Tags: #  
Proper water treatment system understanding will assure that you minimize the time you spend on maintenance and save the money on chemicals. Monitoring of pH & chlorine levels has an important bearing on public health as well as ROI.

As one of the oldest and most common forms of disinfection, chlorine improves water quality by destroying disease-producing microorganisms, and by reacting with other organic and inorganic substances. Chlorine levels must be actively monitored to ensure sufficient chlorine is present for disinfection, as well as to control adverse effects such as taste, odor, and potential reactions with organic matter to form harmful disinfection by products.

Chlorine is a strong oxidising agent that destroys mostly organic pollutants and bacteria and can combine with nitrogen containing compounds, forming chloramines. When dosing chlorine for disinfection, only a portion of the dosed chlorine remains active to actually continue the disinfection process.

Free chlorine can exist in two forms and which form is present is based on the pH.

pH < 7.6 the predominate form is hypochlorous acid (HOCl)
pH > 7.6 the hypochlorite (OCl) form becomes predominate

This is very important when it comes to preventing biological growth in water or keeping a swimming pool safe since hypochlorous acid is 100 times more effective as a sanitizer. Changes in pH value will affect the HOCl equilibrium in relation to the hydrogen and hypochlorite ions.

The efficacy of sanitizers, is dependent on a controlled pH value.

Technology  can keep your spa water fresh and clean and prevent the water becoming potentially harmful.

There is a variety of efficient water treatment systems available which can give very positive results together with proper maintenance.


Chlorine sanitizing systems dispense chlorine and important minerals into the pool water automatically. This maintains a constant residual amount of chlorine, which prevents bacterial growth and eliminates contaminants. The minerals inhibit bacteria growth and soften the feel of the water.These systems remove the need to continually test and adjust multiple chemical levels of the hot tub’s water on a daily and weekly basis.

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.

Save the chemicals!

The main benefit you can get from BL12X line of control/dosing pumps is dosing consent .
BL12X line utilizes a dosing consent feature that will not dose chlorine until the pH value is first corrected since it is possible to have a low ORP value even though there is sufficient chlorine.


The dosing consent feature prevents wastage of chemicals and avoids a higher than necessary chlorine concentration.

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 benefi t 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 fl ow cell is also available. The bypass flow cell allows for calibration and maintenance of the probe without having to shut down the recirculation pump.

Hanna Cloud is a web-based application that connects you to measurement devices such as the BL122 and BL123. Measurements and data storage are accessible from your PC, tablet or phone. Measurements, trends, history, device settings, alarms, and messages are transmitted to your “Dashboard” as your instrument measures and controls your process.


pH Controller and Dosing Pump

Is a system engineered for maintaining the pH of swimming pools, hot tubs, and spas. Typically chlorine, whether liquid or solid, is alkaline and will raise the pH of the water that it is added to.

As the pH increases above pH 7.4, a form of chlorine known as hypochlorite ion (OCl-) increases. This form of chlorine is 100 time less effective at killing bacteria as compared to the other form of chlorine known as hypochlorous acid (HOCl).

For this reason it is important to maintain the correct pH level in order to ensure that the more powerful hypochlorous acid form is available for disinfection.
The BL100 was developed to be an inexpensive solution for the consumer to maintain the ideal pH at all times. Simply insert the probe and injection valve in-line with the recirculation pump and provide the chemical to be dosed.
  • All in one solution for maintaining the proper pH
  • Industrial process probe with 1/2″ NPT threads for insertion into re-circulation line
  • Input for level controller or flow switch
Once you established the sanitation options, all you have to do is test your water regularly so that it remains clean and bather-friendly.
Depending on the sanitation option you have chosen for disinfection there are several options to test the water with practical handheld devices.


Pool Line Portable Photometer

  • pH
  • Alkalinity
  • Free & Total Chlorine
  • Cyanuric Acid

Pool Line Portable Photometer for swimming pools, hot tubs, and spas.

This photometer combines accuracy and ease of use in a simple, portable design. The advanced optical system provides lab-quality accuracy while its user-friendly design is easy for any user making it the perfect photometer for your water quality testing needs.

  • No warm up time before taking a measurement
  • Tutorial mode for step-by-step instructions
  • CAL Check to verify meter performance

HI981954 Pool Line Multiparameter Waterproof Portable Temperature meter is a single tool that allows swimming pool, hot tub, and spa service technicians to measure key water quality parameters for both traditional and electrolytic saltwater pools.
The auto-ranging conductivity/TDS readings can be used for low range readings to track the increase in chemicals as water evaporates from a pool and for the higher range measurement of salt required for the proper electrolysis of sodium chloride to produce chlorine.

The HI981954 can be used for both routine measurements and for process calibration in which the measurement information is then used to update the calibration of process pH, ORP and conductivity meters.

HI981954 offers many advanced features from a large dot matrix LCD that provides for an intuitive user interface in the operation of the meter, log on demand for storing readings, USB port for transferring data, and GLP data for tracking calibration data.

The HI98195 has 5 sensors:

  • pH
  • ORP
  • EC
  • Temperature
  • barometric pressure
The meter is programmed to recalculate in additional 6 interpretative measurements (pH in mV, absolute conductivity, TDS, resistivity, salinity, seawater sigma).
The HI981954 can display up to 11 parameters simultaneously on the large dot matrix LCD.

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