Patent Description:
Hot tubs, spas, and similar water-containing vessels typically comprise open structures adapted to heat a volume of water contained therein. Control means are normally provided for heating the water and for circulating the water via pumps and the like.

Water in hot tubs and spas can present an attractive environment for bacteria and viruses to grow, which can cause infection and disease. These organisms can also affect the oxygen and carbon dioxide concentrations in the water, leading to unbalanced hydrogen ion concentration (pH) levels which can in turn cause irritation of the eyes and skin. Water in hot tubs and spas may also change color due to the growth of organisms therein. To maintain the spa water in a clean and sanitary condition, the water is normally passed through a filter which removes and collects particulate matter. Further, sanitation systems are used to maintain water conditions that discourage bacterial, fungal and viral growth. Sanitation systems for use in the context of hot tubs or spas typically use electrolysis and/or the injection of chemicals to control water quality factors such as Oxidation Reduction Potential (ORP) and pH.

Generally, ORP is a measure of the dissolved oxygen in water expressed in millivolts (mV). A higher ORP is indicative of higher oxygen content and greater oxidizing or cleaning power of the water. pH measures how acidic or basic water is. More specifically, pH is a measure of the relative amount of free hydrogen and hydroxyl ions in the water. Water that has more free hydrogen ions (lower pH) is more acidic while water that has more free hydroxyl ions (higher pH) is more basic. Maintaining the pH of the spa water within an acceptable range is important for user comfort.

Sanitation systems typically include sensors to measure parameters relating to water chemistry, including pH and ORP, and mechanisms to adjust said parameters directly or indirectly. Chemical injection sanitation systems deliver metered doses of one or more chemicals to maintain water chemistry within a selected target range to maintain water clarity and sanitation.

Electrolytic sanitation systems pass electrical current between electrodes, comprising one or more cathodes and one or more anodes, and causes salt molecules (NaCl) in the water to split into sodium (Na+) and chlorine (Cl-) ions. Generation of chlorine sanitizes the water, thus increases the ORP thereof. This process is often preferred to chemical injection, as salt is present in most water supplies and can be easily added otherwise, chlorine is generated at a gradual pace, and there is no need to purchase and transport hazardous chemicals. The chlorine content of water can be estimated as a function of ORP, with higher ORP and lower pH indicating higher chlorine content.

Sanitation systems are often integrated into the water circulation system of the hot tub/spa, such as the pump, which allows for more efficient mixing of chlorine or other sanitation chemicals introduced or generated by the sanitation system into the water. However, such a configuration requires the water circulation system to be running in order to be effective, thus consuming more energy.

Electrolytic sanitation systems typically have designated anodes and cathodes whereby electrical current flows in one direction - from the anode to the cathode. The electrolytic process causes wear on the electrodes, increasing electrical impedance thereof. Over time, the impedance of the electrode plates becomes great enough to render the electrodes unusable, as the current generated by the voltage applied thereto is insufficient to generate enough chlorine, and the electrodes must be replaced.

In typical electrolytic systems, the anode wears out before the cathode. To mitigate uneven wear of the electrodes, some electrolytic sanitation systems reverse the polarities of the electrodes at set time intervals. However, such polarity reversal still does not result in the most efficient use of the electrodes, where both electrodes wear at substantially the same rate.

Some examples are given in <CIT>, <CIT>, <CIT> and <CIT>.

Sanitation systems also typically require replacement of working parts, such as the electrodes, by trained technicians, making replacement of parts inconvenient and costly for the user.

There remains a need for a sanitation system capable of extending the life of its components and allowing for maintenance by the user, thus reducing the need for trained service personnel and frequency of service.

Systems and methods for an improved water sanitation system for hot tubs, spas, and the like are provided. Embodiments of a sanitation system disclosed herein are capable of operating without the pump or water circulation of the spa running, and are capable of selectably operating electrodes of the system in different polarity configurations according to the impedance of the electrodes to extend the life of the electrodes. The life of electrodes is further extended by maintaining voltage and current parameters within optimal ranges and the use of "soft starts". The sanitation system is also configured to monitor the total charge delivered to the electrodes of the system to provide a more accurate measurement of the remaining life of the electrodes. Further, the electrodes are user replaceable for ease of maintenance.

The invention relates to a spa sanitation system according to claim <NUM>.

In an embodiment, the controller of the spa sanitation system is configured to monitor the cumulative charge delivered to the two or more electrodes in each of the first and second polarities.

In an embodiment, the controller of the spa sanitation system operates according to a plurality of operational cycles, and the steps of determining the voltage and current, determining the time period, and selecting a polarity configuration are performed for each operational cycle of the plurality of operational cycles.

In an embodiment, the controller of the spa sanitation system is configured to reverse the polarity configuration of the two or more electrodes if it is detected that the same polarity configuration was selected for a threshold number of consecutive operational cycles.

In an embodiment, the two or more electrodes are located adjacent a side wall of the vessel.

In an embodiment, the spa sanitation system has a module configured to deliver controlled injections of an adjust down chemical to lower a pH level of the water.

In an embodiment, the electrodes are contained in a user replaceable housing.

In an embodiment, the spa sanitation system has a sacrificial anode.

In an embodiment, the spa sanitation system has a salinity sensor.

In an embodiment, the spa sanitation system has a chlorine sensor.

In an embodiment, the spa sanitation system has a turbidity sensor.

In an embodiment, the two or more electrodes are <NUM>-plate electrodes.

The invention further relates to a method for controlling a spa sanitation system of a water-containing vessel according to claim <NUM>.

In an embodiment, the method further comprises turning off pumps of the vessel.

According to the invention, the step of the method of selecting a polarity configuration comprises measuring a first impedance of the two or more electrodes in a first polarity and measuring a second impedance of the two or more electrodes in a second polarity, and selecting the polarity configuration having a lower impedance.

In an embodiment, the steps of the method of turning off the pumps, acquiring ORP measurements, pH measurements, and temperature measurements, determining the voltage and the current, determining the time period, and selecting the polarity configuration are performed in an operational cycle of a plurality of operational cycles.

In an embodiment, the method includes periodically switching the polarity configuration if the same polarity configuration was selected for a threshold number of consecutive operational cycles.

In an embodiment, the method includes monitoring a cumulative charge delivered to the two or more electrodes in each of the first polarity and the second polarity.

In an embodiment, the method includes injecting a pH adjust down chemical into the water if the pH measurements are above a maximum pH threshold.

In an embodiment, the voltage delivered to the two or more electrodes is increased from zero to the determined voltage gradually over a ramp period.

Although a few embodiments have been shown and described, it will be appreciated by those skilled in the art that various changes and modifications can be made to these embodiments without changing or departing from their scope, intent, or functionality. The terms and expressions used in the preceding specification have been used herein as terms of description and not of limitation, and there is no intention in the use of such terms and expressions of excluding equivalents of the features shown and described or portions thereof.

Referring to <FIG>, embodiments of a water sanitation system <NUM> herein comprise at least two electrodes <NUM>, each capable of operating as an anode 22A or a cathode 22C, coupled with a controller <NUM> which operates in a manner to extend the life of the electrodes <NUM> by selecting which of the electrodes <NUM> is designated an anode 22A and a cathode 22C based on relative wear of the electrodes <NUM>. The electrodes <NUM> may be contained within a housing <NUM> and forming part of an electrolytic cell <NUM> for easier handling.

Referring to <FIG>, embodiments herein of the water sanitation system <NUM> are described with reference to a spa or hot tub <NUM>. However, the water sanitation system <NUM> described herein may be used with any suitable body of water, including spas, hot tubs, swim spas and cold tubs.

In an embodiment, the water sanitation system <NUM> comprises the electrolytic cell <NUM> having two or more electrodes <NUM>, a power source <NUM>, a controller <NUM>, an ORP measurement sensor <NUM>, a pH measurement sensor <NUM>, a temperature sensor <NUM>, and a module for delivering an "adjust down" chemical. In the embodiments, the "adjust down" chemical can be muriatic acid, carbon dioxide, sodium bisulfate, vinegar, or another suitable chemical for adjusting pH. The cell <NUM> can be electrically connected to the controller <NUM> and/or power source <NUM> via an electrical cord <NUM> extending therebetween. In embodiments, the ORP measurement sensor <NUM>, the pH measurement sensor <NUM> and the temperature sensor <NUM> may have common components and be housed together. In other embodiments, the sensors <NUM>, <NUM>, <NUM> may be housed separated and/or located apart from each other. In an embodiment, the power source <NUM> and controller <NUM> for the sanitation system <NUM> can be located near the spa control module <NUM> of the spa or hot tub <NUM>, the electrolytic cell <NUM> can be attached to a side wall <NUM> of the spa or hot tub <NUM>, and the ORP measurement sensor <NUM>, pH measurement sensor <NUM>, and temperature sensor <NUM> can be installed near the electrolytic cell <NUM> or at another suitable location in the spa or hot tub <NUM>. In other embodiments, the controller <NUM> can be integrated into the control module <NUM> of the spa. Referring to <FIG>, in embodiments where a sacrificial anode <NUM> is included, the sacrificial anode <NUM> can be installed any location where it is in contact with the water. In embodiments, the sacrificial anode <NUM> is installed in a drain line near the equipment compartment for inspection, and away from the water flow, with a ground cable run to the ground circuit of the spa or hot tub <NUM> electrical system. In embodiments, the sanitation system <NUM> can comprise a turbidity sensor <NUM>, which is a high definition sensor that measures water clarity. In embodiments, the turbidity sensor <NUM> can signal to the sanitation system <NUM> that sanitizer is required to remedy low water clarity. The above components of the sanitation system <NUM> can be connected with wired or wireless means, such as cords wires, radio-frequency, Bluetooth™, and the like.

During the electrolytic sanitation process, electrical current passing between the anode 22A and the cathode 22C in the spa water causes salt molecules in the water to split into sodium and chlorine ions. As seen in <FIG>, the ions created by the electrolytic process appear as gas bubbles G in the water. By locating the electrolytic cell <NUM> under the surface of the water attached to a side wall <NUM> of the spa <NUM>, the water sanitation system <NUM> uses the natural flow caused by the escaping gas G allowing it to circulate water without a pump, thus saving energy.

The water sanitation system <NUM> can estimate the free chlorine (FCL) level of the spa water using Oxidation Reduction Potential (ORP), pH, and temperature measurements obtained from the ORP sensor <NUM>, the pH sensor <NUM>, and the temperature sensor <NUM> of the water sanitation system <NUM>, respectively. With reference to <FIG>, the FCL of the water can be calculated from measured pH, ORP, and temperature using known correlation data. The FCL can then be used to determine whether current must be passed between the electrodes <NUM> to generate additional chlorine, and how much chlorine must be generated. As FCL can be estimated from the ORP, pH, and temperature of the water, the water sanitation system <NUM> does not require a separate chlorine sensor, which has the advantage of reduced cost and not requiring an additional component that may be subject to failure. Further, ORP is a more useful measurement for the cleanliness of water than FCL, as a chlorine sensor would only work where chlorine is the sanitizer used. In contrast, ORP measures the oxygen content in water and its ability to break down contaminants through oxidation, and as such is suitable for use with a wide variety of sanitizers. In embodiments, the ORP measurement sensor <NUM> is configured to at least measure known chemical substances, including FCL. In embodiments, the sanitation system <NUM> may comprise a separate chlorine sensor <NUM>.

As the water sanitation system <NUM> requires sufficient salt in the spa water to generate chlorine therefrom, the water sanitation system <NUM> monitors the salt level in the spa water using a salt estimation algorithm based on measurements of electrode <NUM> impedance and wear, and can prompt the user to add salt if needed. The salt estimation algorithm is based on the measured impedance of the electrodes <NUM> as salt is added to the water. In an embodiment, the operational range of salt concentration in the water is between <NUM> p. m and <NUM> p. Such impedance measurements can be taken using electrodes <NUM> at various stages of wear, for example, using new electrodes <NUM>, <NUM>% worn electrodes <NUM>, <NUM>% worn electrodes <NUM> and <NUM>% worn electrodes <NUM>. Electrode <NUM> wear is determined based on the accumulated charge of the electrode <NUM>, which can be measured in milliamp-hours (mA), as described in further detail below. The salt estimation algorithm uses linear interpolation between known points based on such impedance measurements to estimate salt level. More specifically, the impedance of the electrode <NUM> at known wear and salinity levels can be compared with the actual measured impedance and current wear of the electrodes <NUM> to estimate the salinity of the water. Thus, the water sanitation system <NUM> is controlled to maintain measurements within acceptable levels to provide accurate estimations of FCL in the water. In embodiments, the sanitation system <NUM> may comprise a separate salinity sensor <NUM> for directly measuring salt concentration.

The controller <NUM> of the water sanitation system <NUM> controls the operation of the electrodes <NUM> based on the ORP, pH, and temperature measurements obtained by the various sensors <NUM>,<NUM>,<NUM> of the water sanitation system <NUM>. The controller <NUM> can be configured to operate the electrodes <NUM> to maintain ORP at about a selected set point, for example 740mV, or within a selected range, for example +/- 20mV. In an embodiment, the ORP level can be maintained at three different levels based on user settings: <NUM>-550mV, <NUM>-650mV and <NUM>-750mV. In embodiments, the pH can be maintained at levels between <NUM> and <NUM> and the temperature can be maintained between <NUM> to <NUM> degrees Celsius (<NUM> to <NUM> degrees Fahrenheit). The speed at which the electrolytic process occurs is controlled by the controller <NUM> by adjusting the current through the electrodes <NUM>. The controller <NUM> can also be configured to inject a pH-reducing "adjust down" chemical to maintain the pH of the spa water within a range appropriate for spa occupants, for example between <NUM> and <NUM>.

The controller <NUM> of the water sanitation system <NUM> can be configured to operate in a series of operational cycles. An exemplary operational cycle <NUM> is depicted in <FIG>. At the beginning of the operational cycle <NUM>, at step <NUM>, the electrodes <NUM> as well as the pumps of the spa <NUM>, if present, are turned off. At step <NUM>, the controller <NUM> then waits for residual electrical current in the water from a previous operational cycle to dissipate, for example by waiting for one minute or some other time period. At step <NUM>, the controller <NUM> takes ORP, pH, and temperature measurements using the respective sensors <NUM>,<NUM>,<NUM>. Based on the ORP, pH, and temperature measurements, at step <NUM>, the controller <NUM> determines whether sanitizer needs to be produced to adjust the ORP, or whether the pH must be adjusted, in the present cycle. If sanitizer needs to be produced, the controller <NUM> also determines how much sanitizer should be produced, the voltage and current needed to produce the requisite amount of sanitizer, and what polarity the electrodes <NUM> should be operated in. As discussed in further detail below, the controller <NUM> selects the polarity of the electrodes <NUM> based on the relative wear of the electrodes <NUM> determined by impedance. Likewise, if pH must be adjusted, the controller <NUM> can introduce an appropriate amount of pH adjust-down chemical into the water during the operational cycle to bring the pH to a desired level. The controller <NUM> then either runs the sanitization procedure for the remainder of the operational cycle (step <NUM>) or, if no sanitizer needs to be produced, waits until the next operational cycle and the process repeats (step <NUM>). In an embodiment, an operational cycle can be <NUM> minutes. However, in other embodiments, a different operational period can be selected.

<FIG> is a state machine diagram illustrating on embodiment of the operation of the electrodes in the sanitation system, which illustrates the following states and the transitions therebetween: ORP not charging, charge starting, soft start charging, sampling impedance, charging, disconnecting from charging state, ORP measurement, flipping polarity of electrodes, ramping down charging.

In embodiments, the controller <NUM> can adjust the ORP level to an ORP setpoint, the setpoint being a target value or targeted range, using hysteresis around the setpoint value. For example, if the ORP setpoint is 740mV, the controller <NUM> can be configured to operate the electrodes <NUM> to produce sanitizer when the ORP drops to 720mV or below, and can continue operating until the measured ORP reaches 760mV. The deadband around the ORP setpoint can be selected to maintain the ORP of the spa water within a range in which FCL is most effective, and within the limits of the FCL estimation algorithm. For example, for the 740mV setpoint, the deadband is the range between 720mV and 760mV. In embodiments, a different setpoint and/or a different deadband thereabout can be selected.

Applicant has found that at a current of about 980mA, the electrodes <NUM> have a long life but will only maintain water in a sanitary condition if no new bacteria or organics are introduced into the water. Applicant has further found that about 2400mA is ideal for effective sanitizer production in a non-sanitary environment. In an embodiment, the controller <NUM> can be configured to operate to deliver between 980mA and 2400mA of current depending on how much sanitizer is required based on the water conditions. For example, the controller <NUM> could operate to deliver 2400mA to the electrodes <NUM> for a period to bring the FCL of the water to a desired level, and then deliver 980mA to maintain the FCL level. The controller <NUM> can also be configured to deliver any other level of current within the operating range to the electrodes <NUM>. In embodiments, the controller <NUM> can be configured to deliver current within a different operating range.

The electrolytic process causes wear on the electrodes <NUM> and increases the impedance thereof. Eventually, the impedance of the electrodes <NUM> increases to a point where the power source <NUM> can no longer provide a current sufficient to carry out the electrolytic reaction or generate FCL at a sufficient rate, and the electrode plates <NUM> become unusable and require replacement. Therefore, wear of the electrodes <NUM> can usually be measured by calculating impedance during operation of the electrodes <NUM> from the known voltage required to drive the electrodes <NUM> to provide the desired current. For example, if 5VDC is required to deliver 2400mA to the electrodes <NUM>, then using Ohm's law, the impedance of the electrodes <NUM> is <NUM>.

As mentioned above, each of the electrodes <NUM> of the present water sanitation system <NUM> is capable of being designated as either an anode 22A or a cathode 22C, such that current can flow between the electrodes <NUM> in either direction. At the beginning of each operational cycle, the controller <NUM> decides, based on the relative wear of the electrodes <NUM> determined by impedance, which direction the current should flow. This is done by taking a reading of impedance in each polarity configuration and using the polarity configuration with the lower measured impedance, as less cumulative wear has occurred in that direction.

Applicant has found that electrodes <NUM> wear at different rates, and simply reversing the polarity at regular time intervals, while reducing electrode wear to a degree, does not maximize the life of the electrodes <NUM>. For example, when polarity is reversed at regular time intervals, it was found that nearly all of the electrodes <NUM> had one side worn more than the other. Applicant has found that more efficient use of the electrodes <NUM> is achieved when the impedance of the electrodes <NUM> is measured in each polarity, and the polarity of the electrodes <NUM> is switched based on relative wear of the electrodes <NUM> such that the polarity with lower impedance (indicating less wear) is used. When the relative impedance of a first polarity currently used by the water sanitation system <NUM> becomes higher than a second, opposite polarity, such as by a minimum threshold difference, the controller <NUM> can operate the water sanitation system <NUM> in the second polarity and vice versa. The controller <NUM> can be configured to continue to switch the polarities of the electrodes <NUM> in this manner such that the electrodes <NUM> wear evenly in both polarities. The impedance of the electrodes <NUM> can be measured at the beginning of each operational cycle, during the operation of the electrodes <NUM>, or at any other point during the operation of the sanitation system <NUM>.

In an exemplary embodiment, the water sanitation system <NUM> is configured to supply <NUM> to 2400mA of current to the electrodes <NUM>, and is capable of providing <NUM> to <NUM> VDC of voltage thereto. A new electrode <NUM> can require about <NUM> VDC to draw 2400mA. As the electrode <NUM> wears and its impedance increases, the voltage required to draw 2400mA also increases until the maximum <NUM>. 5VDC is supplied to the electrodes <NUM>. From this point on, as the electrodes <NUM> continue to wear, the current drawn will drop until it reaches 0mA.

The controller <NUM> can further be configured to prompt the user to change the electrodes <NUM> as they approach the end of their usable life. The water sanitation system <NUM> can have a user interface, for example in the control module <NUM> of the spa <NUM>, showing the estimated life remaining in the electrodes <NUM> indicated as a percentage as well as allowing the user to select the level of FCL desired as either low (e.g. <NUM>-550mV), medium (e.g. <NUM>-650mV) or high (e.g. <NUM>-750mV). For example, an electrode life indicator can illuminate a green light until the maximum available voltage is applied to the electrodes. Once maximum voltage is reached, the electrode life indicator illuminates a yellow light until the maximum current that can be drawn falls down to 1000mA, at which point the indicator illuminates a red light to indicate that little chlorine is being produce by the electrodes <NUM>.

As water composition in different geographic regions of the spa can vary, the water sanitation system's <NUM> activity will also vary accordingly. Thus, estimating the remaining life of an electrode <NUM> using time-since-installation or an hour meter may not provide accurate results. Thus, the controller <NUM> can also be configured to maintain a charge counter that logs the cumulative charge delivered to each electrode <NUM> in each polarity configuration, measured in milliamp hours (mAh). This information allows a more accurate determination of the remaining life of the electrodes <NUM>, as tracking the cumulative charge delivered in each polarity takes into account not only how long an electrode <NUM> is run, but the intensity of operation as well. In such embodiments, the electrode life indicator can display electrode life based on the accumulated mAh of the electrode <NUM> in each polarity direction and a predetermined lifespan of the electrode <NUM> in each polarity.

In embodiments, the water sanitation system <NUM> can also include a light emitting diode for displaying what state the controller <NUM> is in. In addition to the charge counter described above, the water sanitation system <NUM> can also keep a record of pH, ORP, voltage, current, impedance, and temperature readings. The water sanitation system <NUM> can further include an internet communications interface that allows staff at spa dealers and factories as well as other technicians to access this information for diagnostic purposes.

When the polarity of the electrodes <NUM> is maintained in one configuration for an extended period of time, the electrodes <NUM> will develop a buildup of "scale" comprising calcium and other minerals. The scale can be shed by reversing the polarity of the electrodes <NUM> for an operational cycle. In embodiments, such polarity reversal can be selected by the controller <NUM> even if reversing the polarity would result in operating the sanitation system <NUM> in a polarity with higher wear. In an embodiment, the water sanitation system <NUM> can reverse the polarity of the electrodes <NUM> at regular intervals, for example every eight operational cycles. In embodiments, the controller <NUM> can be configured to reverse the polarity of the electrodes <NUM> if it is detected that the electrodes <NUM> were operated in the same polarity for a threshold number of consecutive operational cycles, such as eight consecutive cycles.

The life of the electrodes <NUM> can be further extended by using a "soft start" at the beginning of each operational cycle. This process involves gradually ramping up the voltage and/or current to the electrodes <NUM> when the electrolytic process begins during an operational cycle. For example, the voltage or current through the electrodes <NUM> can increase from zero to the selected voltage or current in about <NUM> seconds. Other ramp periods besides <NUM> seconds may be used. In embodiments, one of the current or voltage to the electrodes <NUM> can be fixed while the other parameter is controlled and ramped up. Applicant found that using a soft start can extend the life of the electrodes <NUM> by about <NUM>% or more.

The controller <NUM> of the water sanitation system <NUM> can also be interfaced with the controller module of the spa or hot tub <NUM> such that it can control the pumps thereof (if present). As water movement affects the accuracy of ORP measurements, in embodiments, the controller <NUM> can be configured to direct the controller module of the spa <NUM> to turn off the pumps each time ORP measurements are taken to ensure the accuracy of such measurements, such as at step <NUM> of the exemplary operational cycle <NUM>.

To mitigate corrosion of the electrodes <NUM>, the water sanitation system <NUM> can also incorporate a sacrificial anode <NUM>, for example installed in a drain line near the equipment compartment for inspection, and away from the water flow, with a ground cable run to the ground circuit of the spa or hot tub electrical system. The sacrificial anode <NUM> is made of a metal alloy more active than the electrodes <NUM> it is protecting. In embodiments, the sacrificial anode <NUM> is comprised of zinc.

The electrodes <NUM> in the spa sanitation system can also be configured to allow user replacement thereof. The electrodes <NUM> can be replaced without draining the spa or hot tub <NUM>. With reference to <FIG> and <FIG>, to replace the electrodes <NUM> of the water sanitation system <NUM>, the user can unscrew an electrode housing <NUM> and mount <NUM> from the spa <NUM> and remove the housing and mount assembly from the water. The electrode housing <NUM> can then be removed from the mount <NUM> and replaced with a new housing <NUM> containing new electrodes <NUM>, and the housing <NUM> and mount <NUM> assembly can be reinstalled in the spa <NUM>. The electrode housing <NUM> and mount <NUM> can be configured to form a watertight assembly when coupled, such that water cannot come into contact with electrical components therein when the assembly is removed from the spa <NUM>.

Claim 1:
A spa sanitation system (<NUM>) for use with a water-containing vessel, comprising:
two or more electrodes (<NUM>);
an oxidation reduction potential (ORP) sensor (<NUM>);
a pH sensor (<NUM>);
a temperature sensor (<NUM>);
a power source (<NUM>); and
a controller (<NUM>) operatively connected to the power source, pH sensor (<NUM>), temperature sensor (<NUM>), ORP sensor (<NUM>), and the two or more electrodes (<NUM>), the controller (<NUM>) configured to:
determine a voltage and a current to be delivered to the two or more electrodes (<NUM>);
determine a time period for which to run the two or more electrodes (<NUM>); and
select a polarity configuration of the two or more electrodes (<NUM>);
wherein the polarity configuration is selected from a first polarity where a first electrode (<NUM>) of the two or more electrodes (<NUM>) acts as anode and a second electrode (<NUM>) of the two or more electrodes (<NUM>) acts as cathode, or a second polarity where the first electrode (<NUM>) of the two or more electrodes (<NUM>) acts as cathode and the second electrode (<NUM>) of the two or more electrodes (<NUM>) acts as anode; and
wherein the controller (<NUM>) is configured to measure impedance of the two or more electrodes (<NUM>) in the first polarity, and is configured to measure impedance of the two or more electrodes (<NUM>) in the second polarity;
wherein the controller (<NUM>) is configured to select the polarity configuration with the lower impedance and to switch the polarity configuration such that the polarity configuration with the lower impedance is used.