pH Explained

pH is a numerical relationship between the number of hydrogen and hydroxyl ions in a solution. In clean fresh water, the pH value should be about 7.0. This value is chemically neutral (neither acid or alkaline). Water for consumption should be between pH 6.5 and 7.5. Also, water in this range (pH 7.2 is ideal) is more responsible to chemical disinfection using oxidizing sanitizers of the type widely used in water treatment systems, recreational pool and spas.

ORP Explained…..

ORP stands for Oxidation-Reduction Potential, sometimes referred to as Redox Potential. In practical terms, it is a measurement of the efficiency of a chemical additive in water to kill microbes. ORP is the only practical method we have to electronically monitor sanitizer effectiveness. When sanitizing water for consumption, a strong oxidizer is added, e.g. chlorine, bromine, ozone, etc. and, at appropriate levels, the oxidizer kills the biological contaminants in the eliminating the health threat. As a result, some of the oxidizer is “spent”. The remaining or residual oxidizer/sanitizer must be at an appropriate level to destroy new biological threats when they reappear. Therefore, when sanitizing water for consumption or recreational use in a pool or spa the residual oxidizer level is important. If the ORP is too low, new contaminants in the water might become a hazard.

The SmartSensor™ ORP circuit detects the residual or remaining oxidizer and continually reports its ORP or oxidizing power to provide the operator with assurances that the water is fit to drink. The SmartSensor™ detects the residual oxidizer present in the water in real time and gives the user an easy to see and accurate view of the quality of ones’ pool or spa water. ORP is reported in millivolts. (The World Health Organization suggested that a minimum of +650 millivolts should be maintained for pool or spa use).

All automated water chemistry control systems depend on ORP measurements to work. Long time pool and spa service industry professionals  know the routine involved in maintaining proper water chemistry. First test the water, then adjust it to recommended chemical levels then retest to confirm and mitigate the risk.

 

It is no secret that chemical maintenance of pool and spa water is a fairly complicated balancing act. One must maintain sanitizer residual at a level sufficient to protect swimmers and bathers from the invasion of unwanted - and possibly harmful - plant and microbe life. One must maintain the pH of the water at a level that assures the sanitizer works effectively and at the same time protect the pool shell and equipment from corrosion or scaling and the bathers from discomfort or irritation.

Of all the factors involved in pool chemical maintenance, the most important are the level of residual sanitizer and pH. These are the chemical tests performed most frequently and these are parameters with which we are most concerned with. Electronic ORP and and pH sensors allow us to monitor and control sanitizer residual and pH automatically. In a light usage residential pool this may simply be a great convenience. However, in a public or semi-public pool or spa – which is regulated by local health authorities - SmartSensor™ offers dependable, accurate, continuous water chemistry monitoring to meet your customers’, regulator’s and insurer’s requirements.

In order to obtain control of water chemistry there has to be some method of monitoring both the residual sanitizer and the pH and them using the information to chemically treat the water. That's where ORP enters the picture. Chemicals like chlorine, bromine, and ozone are all oxidizers. It is their ability to oxidize - to "steal" electrons from other substances - that makes them good water sanitizers, because in altering the chemical makeup of unwanted organisms, both plants and microbes, they kill them. Then they "burn up" the remains, leaving a few harmless chemicals as the by-product. Of course, during the oxidation process, all of these oxidizers are reduced - so they lose their ability to further oxidize things. They may combine with other substances in the water, or their electrical charge may simply be "used up." To make sure that the chemical process continues to the very end, these must have a high enough concentration of oxidizer in the water to do the whole job. "Potential" is a word that refers to ability rather than action. Therefore ORP gives an indication of the potential efficiency of the sanitizing agent.

World Health Organization Guidelines for Safe Recreational Waters
Volume 2 ‑ Swimming pools and similar recreational‑water environments
5.10.4 OxidationBreduction potential (ORP)

The oxidation-reduction potential (also known as ORP or redox) can also be used in the operational monitoring of disinfection efficacy. In general terms for swimming pools and similar environments, levels in excess of 720 mV measured using a silver/ silver chloride electrode or 680 mV using a calomel electrode suggest that the water is in good microbial condition.@http://www.who.int/water_sanitation_health/bathing/bathing2/en/