Patent Publication Number: US-2003234212-A1

Title: Mineral water making apparatus

Description:
BACKGROUND OF THE INVENTION  
       [0001] 1. Field of the Invention  
       [0002] The present invention relates to a mineral water making apparatus for making mineral water by adding mineral components to raw water.  
       [0003] 2. Description of the Related Art  
       [0004] Heretofore, as a mineral water making apparatus of this kind, an apparatus wherein mineral stone and a filter medium for removing foreign substances are placed in a water tank has been commonly used. When raw water such as tap water is passed through the water tank, mineral components are added to the tap water, and drinking water containing minerals are provided.  
       [0005] However, the quantity of mineral components actually added to the drinking water in such a mineral water making apparatus is extremely small (quantity of added mineral components: 50 ppm or less as general hardness (GH)), which is unsatisfactory as mineral-containing drinking water.  
       [0006] In order to solve such a problem, a mineral water making apparatus disclosed in Japanese Patent Application Laid-Open No. 6-190379 (1994) was proposed. In this mineral water making apparatus, since carbon dioxide gas was injected into tap water to increase the concentration of free carbon dioxide, and the tap water was brought into contact with a porous body supporting calcium carbonate, the mineral component was eluted in short time, and mineral-containing drinking water of a desired mineral concentration could be made and provided.  
       [0007] However, this mineral water making apparatus had a problem in that a gas cylinder for injecting carbon dioxide gas was required, increasing the costs and enlarging the size of the apparatus. In addition, since the quality of raw water affected the eluting rate of the mineral components, the apparatus had another problem in that it could not maintain the mineral concentration. Furthermore, the apparatus had another problem in that the mineral components deposited in the water intake pipe when the mineral concentration elevated needlessly.  
       SUMMARY OF THE INVENTION  
       [0008] In view of the above-described problems in conventional mineral water making apparatuses, the object of the present invention is to provide a mineral water making apparatus of a simple structure that can improve the mineral elution rate of the mineral eluting material, can maintain the mineral concentration of mineral water constant, and can inhibit the deposition of the mineral components.  
       [0009] The first invention is a mineral water making apparatus comprising a water tank having a mineral eluting material disposed therein, a water supply pipe for introducing raw water such as tap water into the water tank, and a water intake pipe for intaking mineral water produced in the water tank; further comprising an acidic food-additive supply apparatus for supplying an acidic food additive into the water tank.  
       [0010] According to the first invention, since the acidic food-additive is supplied into the water tank, and the acid concentration in the water tank rises, the mineral elution rate of the mineral eluting material is improved, and the mineral concentration of mineral water rises.  
       [0011] The second invention is a mineral water making apparatus comprising a water tank having a mineral eluting material disposed therein, a water supply pipe for introducing raw water such as tap water into the water tank, and a water intake pipe for intaking mineral water produced in the water tank; further comprising an acidic food-additive supply apparatus for supplying an acidic food additive into the water intake pipe.  
       [0012] According to the second invention, since the acidic food-additive is added to the mineral water flowing in the intake pipe, the pH of the mineral water can be controlled, and the deposition of the mineral components in the intake pipe can be inhibited, preventing the clogging of the intake pipe.  
       [0013] The third invention is a mineral water making apparatus comprising a water tank having a mineral eluting material disposed therein, a water supply pipe for introducing raw water such as tap water into the water tank, and a water intake pipe for intaking mineral water made in the water tank; wherein an acidic food additive is disposed in the water tank.  
       [0014] According to the third invention, since both the mineral eluting material and the acidic food additive are disposed in the water tank, the water in the water tank is constantly acidified, and mineral water of a high mineral concentration can be made in short time. The mixture of the mineral eluting material and the acidic food additive may also be disposed. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0015]FIG. 1 is a water circuit diagram showing a mineral water making apparatus according to the first embodiment;  
     [0016]FIG. 2 is a water circuit diagram showing a mineral water making apparatus according to the second embodiment;  
     [0017]FIG. 3 is a water circuit diagram showing a mineral water making apparatus according to the third embodiment;  
     [0018]FIG. 4 is a block diagram showing a drive control circuit of a solenoid valve according to the third embodiment;  
     [0019]FIG. 5 is a flow chart showing the control of a solenoid valve according to the third embodiment;  
     [0020]FIG. 6 is a water circuit diagram showing a mineral water making apparatus according to the fourth embodiment;  
     [0021]FIG. 7 is a block diagram showing a drive control circuit of a solenoid valve according to the fourth embodiment;  
     [0022]FIG. 8 is a flow chart showing the control of a solenoid valve according to the fourth embodiment;  
     [0023]FIG. 9 is a water circuit diagram showing a mineral water making apparatus according to the fifth embodiment;  
     [0024]FIG. 10 is a water circuit diagram showing a mineral water making apparatus according to the sixth embodiment;  
     [0025]FIG. 11 is a water circuit diagram showing a mineral water making apparatus according to the seventh embodiment;  
     [0026]FIG. 12 is a water circuit diagram showing a mineral water making apparatus according to the eighth embodiment;  
     [0027]FIG. 13 is a front sectional view showing a mineral water making apparatus according to the eighth embodiment;  
     [0028]FIG. 14 is a side sectional view showing a mineral water making apparatus according to the eighth embodiment;  
     [0029]FIG. 15 is an enlarged sectional view showing a mixture according to the eighth embodiment; and  
     [0030]FIG. 16 is a water circuit diagram showing a mineral water making apparatus according to the ninth embodiment. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
     [0031]FIG. 1 shows the first embodiment of a mineral water making apparatus according to the present invention.  
     [0032] The mineral water making apparatus has a water tank  10  for making mineral water. A mineral eluting material  11  is disposed in the water tank  10 . As the mineral eluting material  11 , powdered or granulated coral sand, Mai-fan-shih (healstone), mineral stone and the like are used. By passing water through the mineral eluting material, mineral components are eluted into the water, and mineral water is made.  
     [0033] A water-supply pipe  12  is linked to the upper portion of the water tank  10 , and tap water (raw water) is supplied into the water tank  10  through the water-supply pipe  12 . An acidic food-additive supply apparatus  13  is connected to the water-supply pipe  12 . The acidic food-additive supply apparatus  13  is composed of a tank  13   a , a derivation pipe  13   b  connected to the bottom of the tank  13   a  and to the water-supply pipe  12 , and a solenoid valve  13   c  for opening and closing the derivation pipe  13   b . The tank  13   a  accommodates an acidic food additive  13   d . As the acidic food additive  13   d , an aqueous solution wherein a food additive that exhibits acidity, for example, citric acid, DL-malic acid, phosphoric acid, and fumaric acid, is used. Of these acidic food additives  13   d , citric acid and DL-malic acid have the effect of improving the intake efficiency of mineral components when the mineral water is taken in human bodies.  
     [0034] A water intake pipe  14  connected to a faucet or the like is linked to the lower portion of the water tank  10 . A pump  15  is installed in a water intake pipe  14 . While a pump  15  is activated, mineral water made in the water tank  10  is supplied to the faucet through the water intake pipe  14 .  
     [0035] According to this embodiment, when the solenoid valve  13   c  is opened, the acidic food additive  13   d  is added in tap water flowing in the water-supply pipe  12 , and the acidity of water stored in the water tank  10  rises. The increase of the level of acid water improves the rate of mineral elution of the mineral eluting material  11 .  
     [0036] Calcium carbonate (CaCO 3 ) is used as the mineral eluting material  11 , it causes the following chemical reaction: 
     CaCO 3 +2H + →Ca 2+ +H 2 O+CO 2   
     [0037] By the elution of mineral ions (Ca 2+ ) as described above, drinking water having a high mineral concentration can be made.  
     [0038]FIG. 2 shows the second embodiment of a mineral water making apparatus according to the present invention. In the first embodiment described above, the acidic food additive  13   d  is supplied into the water tank  10  through the water-supply pipe  12 . Whereas in the second embodiment, the acidic food additive  13   d  is directly supplied into the water tank  10 .  
     [0039] In the first embodiment described above, the operation for supplying the acidic food additive  13   d  follows the water-supply operation of tap water; while in the second embodiment, the pathway for supplying the acidic food additive is separated from the pathway for supplying tap water, the acidic food additive  13   d  can be supplied into the water tank  10  as desired regardless of the supply of tap water. Since other constitutions and operations are same as in the first embodiment, the description thereof will be omitted.  
     [0040] FIGS.  3  to  5  show the third embodiment of a mineral water making apparatus according to the present invention. The same component parts as in the above-described first embodiment will be denoted by the same reference numerals and characters, and the description thereof will be omitted.  
     [0041] In this embodiment, the quantity supplied of the acidic food additive  13   d  is controlled on the basis of the quality, i.e., the pH value of tap water flowing in the water-supply pipe  12 . A pH sensor  16  for sensing the pH value of tap water is installed in the water-supply pipe  12 . A flowing-water sensor  17  for sensing the presence of flowing water in the water intake pipe  14  is installed in the water intake pipe  14 .  
     [0042] As FIG. 4 shows, the mineral water making apparatus has a controller  18  composed of microcomputers as control means for controlling the solenoid valve  13   c . The controller  18  has I/O ports  18   a  and  18   b , a CPU  18   c , and a memory  18   d . The memory  18   d  stores the setting-open time TA of the solenoid valve  13   c  in advance. The time TA determines the adding quantity of the acidic food additive  13   d . The time TA is set on the basis of an empirical rule that the desired mineral concentration in the mineral water can be achieved when the pH of tap water is normal, and the solenoid valve  13   c  is opened for the time TA. The controller  18  controls the solenoid valve  13   c  through a solenoid valve drive circuit  19  as shown in the flow chart of FIG. 5.  
     [0043] First, as described above, the setting-open time TA of the solenoid valve  13   c  has been stored in the memory  18   d  (S 1 ). The pH value of tap water in the water-supply pipe  12  is sensed by the pH sensor  16 , and measured by the controller  18  (S 2 ). If the measured pH value is high, the mineral-elution rate lowers, and if the measured pH value is low, the mineral-elution rate rises. Therefore, while the measured pH value is high, the time TA is lengthened to increase the supply quantity of the acidic food additive  13   d ; whereas when the measured pH value is low, the time TA is shortened to decrease the supply quantity of the acidic food additive  13   d . In other words, the setting-open time TA is corrected to time TA 1  in response to the pH value of tap water (S 3 ). Under these circumstances, the flowing-water sensor  17  monitors whether water flows in the water intake pipe  14  or not (whether there is water intake or not) (S 4 ). When the flowing-water sensor  17  senses flowing water, the solenoid valve  13   c  is opened for time TA 1  (S 5 ). Thereby, since the acidic food additive  13   d  corresponding to the pH value of tap water is supplied into the water tank  10 , the concentration of the produced mineral water is maintained constant.  
     [0044] FIGS.  6  to  8  show the fourth embodiment of a mineral water making apparatus according to the present invention. The same component parts as in the above-described third embodiment will be denoted by the same reference numerals and characters, and the description thereof will be omitted.  
     [0045] In the third embodiment, the pH sensor  16  is installed in the water-supply pipe  12 , and the open time of the solenoid valve  13   c  is controlled on the basis of the quality of tap water flowing in the water-supply pipe  12 . Whereas in this embodiment, the pH sensor  16  is installed in the water intake pipe  14 , and the open time of the solenoid valve  13   c  is controlled on the basis of the quality of mineral water flowing in the water intake pipe  14 .  
     [0046] As FIG. 7 shows, in the same way as in the above-described third embodiment, the fourth embodiment has a controller  18  having I/O ports  18   a  and  18   b , a CPU  18   c , and a memory  18   d . The memory  18   d  stores the setting-open time TA of the solenoid valve  13   c  in advance as in the above-described third embodiment. The control of the solenoid valve  13   c  will be described referring to the flowchart of FIG. 8.  
     [0047] First, as described above, the setting-open time TA of the solenoid valve  13   c  has been stored in the memory  18   d  (S 1 ). The pH value of mineral water in the water intake pipe  14  is sensed by the pH sensor  16 , and measured by the controller  18  (S 2 ). While the measured pH value is high, the mineral-elution rate lowers, and while the measured pH value is low, the mineral-elution rate rises. Therefore, when the measured pH value is high, the time TA is lengthened to increase the supply quantity of the acidic food additive  13   d ; whereas when the measured pH value is low, the time TA is shortened to decrease the supply quantity of the acidic food additive  13   d . In other words, the setting-open time TA is corrected to time TA 2  in response to the pH value of the mineral water (S 3 ). The system is allowed to stand in such a state, and the flowing-water sensor  17  monitors whether water flows in the water intake pipe  14  or not (whether there is water intake or not) (S 4 ). When the flowing-water sensor  17  senses flowing water, the solenoid valve  13   c  is opened for time TA 2  (S 5 ). Thereby, since the acidic food additive  13   d  corresponding to the pH value of the mineral water is supplied into the water tank  10 , the concentration of the produced mineral water is maintained constant.  
     [0048] In the third and fourth embodiments, as described above, although water quality is sensed by using the pH sensor  16  to maintain the mineral concentration of the mineral water constant, the present invention is not limited thereto. For example, a conductivity sensor (not shown) for sensing the electric conductivity of tap water or mineral water may be installed in place of the pH sensor  16  to control the open time of the solenoid valve  13   c  on the basis of the electric conductivity sensed by the conductivity sensor.  
     [0049] More specifically, while the electric conductivity of tap water or mineral water is low, the mineral concentration is high. On the other hand, while the electric conductivity of tap water or mineral water is high, the mineral concentration is low. Therefore, when the measured electric conductivity is low, the open time of the solenoid valve  13   c  is shortened to decrease the quantity of mineral elution. On the other hand, when the measured electric conductivity is high, the open time of the solenoid valve  13   c  is lengthened to increase the quantity of mineral elution. Thereby, the mineral concentration in the mineral water can be maintained at a predetermined value.  
     [0050]FIG. 9 shows the fifth embodiment of a mineral water making apparatus according to the present invention. The above-described embodiments have constitutions wherein the acidic food additive  13   d  is added before mineral treatment. Whereas this embodiment has a constitution wherein all or a part of the produced mineral water is returned into the water tank  10 , and the acidic food additive  13   d  is added to the returned water. The same component parts as in the above-described first embodiment will be denoted by the same reference numerals and characters, and the description thereof will be omitted.  
     [0051] Specifically, a water-circulating pipe  20  is installed to connect to the downstream side of the pump  15  on the intake pipe  14  and to the upper portion of the water tank  10 . Thereby, as broken-line arrows in FIG. 9 show, mineral-water circulation means that can circulate the mineral water in the water tank  10  is constituted. More specifically, this mineral-water circulation means is constituted so that the mineral water in the water tank  10  is circulated in the order of, the water intake pipe  14 →the pump  15 →the water intake pipe  14 →the mineral-water circulating pathway  20 →the water tank  10 . A derivation pipe  13   b  of the acidic-food-additive supply apparatus  13  is also connected to the middle of the mineral-water circulating pathway  20 .  
     [0052] In the mineral water making apparatus according to this embodiment, the faucet of the water intake pipe  14  is closed, and simultaneously, the solenoid valve  13   c  of the acidic-food-additive supply apparatus  13  is opened, then the pump  15  is activated. Thereby, since all the mineral water flows out of the water tank  10  as shown by the broken-line arrows in FIG. 9, and the acidic food additive  13   d  is added to the mineral water, the concentration of minerals in the water tank  10  can be raised.  
     [0053] The faucet of the water intake pipe  14  is opened, and simultaneously, the solenoid valve  13   c  of the acidic-food-additive supply apparatus  13  is opened, then the pump  15  is activated. Thereby, the mineral water passing through the water intake pipe  14  is guided to the faucet, a part of the mineral water passing through the water intake pipe  14 , which contains the acidic food additive  13   d , enters in the mineral-water circulating pathway  20 , and returns to the water tank  10 . Therefore, the acidity in the water tank  10  is raised by the acidic food additive  13   d  added to the mineral water, and the mineral water having a high mineral concentration can be obtained.  
     [0054] As in the above-described third and fourth embodiments, a pH sensor  16  or a conductivity sensor may be installed to determine the open time of the solenoid valve  13   c  depending on the quality of tap water or mineral water.  
     [0055]FIG. 10 shows the sixth embodiment of a mineral water making apparatus according to the present invention. In the above-described embodiments, the acidic food additive  13   d  is supplied into the water tank  10 . Whereas in this embodiment, the acidic food additive  13   d  is supplied into the water intake pipe  14 . The same component parts as in the above-described first embodiment will be denoted by the same reference numerals and characters, and the description thereof will be omitted.  
     [0056] Specifically, the derivation pipe  13   b  of the acidic-food-additive supply apparatus  13  is connected to the water intake pipe  14 . The solenoid valve  13   c  is opened or closed to control the supply of the acidic food additive  13   d  to the water intake pipe  14 .  
     [0057] If the mineral concentration is needlessly high, eluted minerals may be precipitated and mixed in beverage, and mineral water unsuitable for beverage may be made. Therefore, in the mineral water making apparatus according to this embodiment, when intaking mineral water, the solenoid valve  13   c  is opened to introduce the acidic food additive  13   d  into the water intake pipe  14 . Thereby, the mineral eluting rate is improved, and no mineral components extract in the water intake pipe  14 .  
     [0058] As in the above-described third and fourth embodiments, a pH sensor  16  or a conductivity sensor may be installed to determine the open time of the solenoid valve  13   c  depending on the quality of tap water or mineral water. The flow rate of the acidic food additive  13   d  is controlled using not only the solenoid valve  13   c , but a pump (not shown) may be used in place of the solenoid valve  13   c.    
     [0059]FIG. 11 shows the seventh embodiment of a mineral water making apparatus according to the present invention. In the above-described embodiments, the acidic food additive is placed outside the water tank  10 . Whereas in this embodiment, the acidic food additive  13   d  is placed in the water tank  10 . The same component parts as in the above-described first embodiment will be denoted by the same reference numerals and characters, and the description thereof will be omitted.  
     [0060] Specifically, as well as a granulated or powdered acidic food additive, a granulated or powdered mineral eluting material is mixed to form a mixture  21 , and the mixture  21  is disposed in the water tank  10 . According to this embodiment, the eluted minerals can be easily acidified, and mineral water having a high mineral concentration can be made.  
     [0061] FIGS.  12  to  15  show the eighth embodiment of a mineral water making apparatus according to the present invention. In the above-described first to seventh embodiments, only the mineral eluting material  11  is disposed in the water tank  10 , and a liquid acidic food additive  13   d  is used. Whereas in this embodiment, an electrode for eluting minerals is disposed in the water tank as well as a mineral eluting material, and a solid acidic food additive is used. A mineral water making apparatus according to the eighth embodiment will be described referring to FIGS.  12  to  15 .  
     [0062] The mineral water making apparatus has a water tank  100 , a water-supply pipe  200  for supplying raw water such as tap water into the water tank  100 , and a water-intake pipe  300  for guiding the mineral water made in the water tank  100  to a faucet (not shown) using a pump  301 .  
     [0063] First, the structure of the water tank  100  will be described in detail referring to FIGS. 13 and 14. The water tank  100  is formed in a flat box shape, and the interior thereof is substantially divided, into upper and lower portions by a diaphragm  101  that can pass water. Above the diaphragm  101 , a water storage chamber  102  for supplying tap water is formed. Below the diaphragm  101 , an electrolysis chamber  103  for electrolyzing water is formed.  
     [0064] A water conduit tube  104  to be connected to the water-supply pipe  200  is installed on the upper plate of the water storage chamber  102 , and tap water is introduced into the water storage chamber  102  through the water conduit tube  104 . A water-level detector  105  is installed in the water storage chamber  102 . The water-level detector  105  has a structure to detect the up-and-down motion of a float  105   a  using upper and lower micro-switches  105   b . The supply and stop of tap water is controlled on the basis of detection signals from each of the micro-switches  105   b  to maintain the water level in the water storage chamber  102  as predetermined. A guide plate  106  is also installed in the water storage chamber  102 . The guide plate  106  guides tap water supplied from the water conduit tube  104  toward the central portion of the water storage chamber  102 , so that the tap water flows from the central portion of the water storage chamber  102  to the entire water storage chamber  102 . The reference numeral  107  denotes an overflow pipe for draining water exceeding the allowable quantity.  
     [0065] A plurality of mixtures  108  and a plurality of positive and negative pairs of electrodes for eluting minerals  109   a  and  109   b  are alternately disposed in the electrolysis chamber  103 . The terminal  109   c  of each electrode  109   a  and  109   b  passes through the diaphragm  101  and protrudes from the upper plate of the water storage chamber  102  to be connected to the power supply.  
     [0066] The mixture  108  is composed of a mineral eluting material  108   a  and a conductive material  108   b  as shown in FIG. 15. As the mineral eluting material  108   a , powdered or granulated coral sand, healstone, mineral stone or the like is used. On the other hand, as the conductive material  108   b , any one of powdered activated charcoal, granulated activated charcoal, fibrous activated charcoal, wood charcoal, carbon black, a gold-, silver-, or platinum-based metal; or the mixture thereof is used. Since a carbon-based, or gold-, silver-, or platinum-based metal is used as the conductive material  108   b , even if the conductive material is eluted, it is harmless to human bodies. If activated charcoal is used as the conductive material  108   b , the activated charcoal may be coated with silver to improve electric conductivity. Although the mixture  108  is composed of the mineral eluting material  108   a  and the conductive material  108   b , as described above, water can pass through the mixture  108 . In order to facilitate assembly and maintenance, the mixture  108  may be filled in a water-permeable container in advance, and the container may be disposed in the electrolysis chamber  103 . In this case, the container filled with powdered or granulated mineral eluting material  108   a  and the conductive material  108   b  is used.  
     [0067] A DC voltage from a DC power source (not shown) is impressed between one electrode for eluting minerals  109   a  and the other electrode for eluting minerals  109   b , and the one electrode for eluting minerals  109   a  constitutes a positive electrode, and the other electrode for eluting minerals  109   b  constitutes a negative electrode. The voltage, polarity, impressing time and the like of the DC power source are controlled by the control unit (not shown).  
     [0068] While a DC voltage is applied between the electrodes for eluting minerals  109   a  and  109   b  of the mineral water making apparatus according to this embodiment, in the side of the electrode for eluting minerals  109   a , which is the positive electrode, water reacts as follows: 
     2H 2 O→4H + +O 2 +4e −   
     [0069] thus the hydrogen ion concentration of the water in the positive electrode side rises to generate acidic water. On the other hand, in the side of the electrode for eluting minerals  109   b , which is the negative electrode, water reacts as follows: 
     4H 2 O+4e − →2H 2 +4OH −   
     [0070] Thus, alkaline water is generated in the negative electrode side. When calcium carbonate (CaCO 3 ) is used as the mineral eluting material  108   a , the calcium carbonate reacts with acidic water as follows: 
     CaCO 3 +2H + →Ca 2+ +H 2 O+CO 2   
     [0071] Thus, mineral ions (Ca 2+ ) are eluted.  
     [0072] Here, since the mineral eluting material  108   a  is an insulator, it may act as the factor to lower conductivity between the electrodes for eluting minerals  109   a  and  109   b . However, since a conductive material  108   b  is mixed with the mineral eluting material  108   a  in the mineral water making apparatus of this embodiment, the efficiency of electrolysis is not lowered, and furthermore, the efficiency of mineral eluting is not lowered.  
     [0073] A confluence chamber  110  for combining the mineral water generated in the electrolysis chamber  103  is disposed on the lower portion of the water tank  100 . The mineral water flowing in the confluence chamber  110  flows down to the water-intake pipe  300  through the derivation pipe  111 .  
     [0074] Next, the structure of the water-supply pipe  200  side will be described referring to FIG. 12. An acidic-food-additive supply apparatus  400  accommodating an acidic food additive is installed on the water-supply pipe  200  in the upstream side of the water tank  100 . The acidic-food-additive supply apparatus  400  is installed from the middle of the water-supply pipe  200  in parallel to a part of the water-supply pipe  200  through the branch pipe  401 . An open-close valve  402  is installed on the upstream side of the branch pipe  401 . The supply of water to the acidic-food-additive supply apparatus  400  is controlled by the open-close operation of the open-close valve  402 . Here, as in the above-described first embodiment, the acidic food additive may be any food additive that exhibits acidity, such as citric acid, DL-malic acid, phosphoric acid, and fumaric acid. The acidic food additive is stored in the acidic-food-additive supply apparatus  400  in the form of powdered or granulated solid so as to be efficiently eluted into tap water.  
     [0075] According to this embodiment, mineral components are eluted from the mineral eluting material  108   a  by impressing a DC voltage between electrodes for eluting minerals  109   a  and  109   b . When the pump  301  is activated, tap water flows as arrows in FIGS.  12  to  14  show, and mineral water flows to the faucet.  
     [0076] In taking the mineral water, when the open-close valve  402  is opened, a part of tap water flows into the acidic-food-additive supply apparatus  400 , and the rise of pH in the water tank  100  is inhibited. Thereby, the lowering of mineral dissolution is prevented, and the mineral water of a high mineral concentration can be formed, and the precipitation of the mineral components can also be prevented.  
     [0077] Although the open-close valve  402  is installed in the branch pipe  401 , a flow regulating valve (not shown) may be installed in place of the open-close valve  402 . Thereby, the eluting quantity of the acidic food additive can be optionally controlled, and the mixing of excessive additive can be prevented.  
     [0078] In the same as in the above-described third and fourth embodiments, a pH sensor  16  or a conductivity sensor may be installed in the water-supply pipe  200  or the water-intake pipe  300  to control the open time of the open-close valve  402  on the basis of the quality of tap water or mineral water.  
     [0079]FIG. 16 shows the ninth embodiment of a mineral water making apparatus according to the present invention. The same constituting parts as in the above-described eighth embodiment will be denoted by the same reference numerals and characters, and the description thereof will be omitted.  
     [0080] The above-described eighth embodiment has the structure wherein the acidic food additive is added in the upstream side of the water tank  100 . Whereas in this embodiment, a mineral-water circulating pipe  420 , whose one end is connected to the downstream side of the pump  301  in the water-intake pipe  300 , and whose other end is connected to the water-supply pipe  200 , is installed. An acidic-food-additive supply apparatus  421  is installed in the mineral-water circulating pipe  420 . The acidic-food-additive supply apparatus  421  accommodates a powdered or granulated acidic food additive as the acidic-food-additive supply apparatus  400  in the eighth embodiment.  
     [0081] According to this embodiment, while the faucet is opened and the pump  301  is activated, a part of the mineral water from the water-intake pipe  300  returns to the water tank  100  as the arrows in FIG. 16 show. Thereby, the mineral concentration of the mineral water can be raised. Since an acidic food additive is added to the mineral water returning to the water tank  100 , the rise of pH in the electrolysis vessel can be inhibited, and the mineral concentration of the mineral water can further be raised.  
     [0082] Although the other end of the mineral-water circulating pipe  420  is connected to the water-supply pipe  200 , the other end of the mineral-water circulating pipe  420  may be directly connected to the water tank  100 .  
     [0083] As in the above-described fifth embodiment, when the pump  301  is activated in the state that the faucet is closed, since all the mineral water flowing in the water-intake pipe  300  returns to the water tank  100  through the mineral-water circulating pipe  420 , the mineral concentration of the mineral water in the water tank  100  further rises. Other constitutions and functions are the same as the constitutions and functions of the eighth embodiment.