EP4330197A1

EP4330197A1 - Equipment for the management and treatment method of water supplied to medical devices and in particular to dental units

Info

Publication number: EP4330197A1
Application number: EP21734953.9A
Authority: EP
Inventors: Alessandro FOLLINI
Original assignee: Dtf Technology Srl
Current assignee: Dtf Technology Srl
Priority date: 2021-04-28
Filing date: 2021-04-28
Publication date: 2024-03-06
Also published as: WO2022229989A1

Abstract

Equipment and method for treating water supplied to medical devices, in particular to dental units, comprising: a first tank (2) for collecting water coming from a water supply network, said tank (2) having a water inlet conduit (5) connectable to said water supply network and configured to supply water into the tank (2) by gravity; at least one conduit (7) for picking up the water contained in the tank (2), connectable to at least one outlet and having a pump (8) for supplying a predetermined amount of water to said outlet; at least a level sensor (11) associated to said first tank (2) for detecting a minimum LI and a maximum L2 level of water in said first tank (2); and an ozone generator (15), operably engaged inside the first tank (2) for ozonating the water contained in the first tank (2).

Description

DESCRIPTION

EQUIPMENT FOR THE MANAGEMENT AND TREATMENT METHOD OF WATER SUPPLIED TO MEDICAL DEVICES AND IN PARTICULAR

TO DENTAL UNITS

Technical Field

The present invention relates to equipment and a related method for the management, treatment and purification of water supplied to medical devices, such as in particular dental units or other devices intended for medical/surgical treatment.

In greater detail, the present invention relates to equipment which is interposed between the water supply network and one or more dental units in order to supply sanitised and purified water to the outlets provided in the aforesaid unit. This equipment is provided in particular to meet current regulations in terms of water treatment levels, in particular UNI EN ISO 7494-2:2015.

State of the art

As known, medical devices are served by a source of appropriately treated water that can be used for different purposes depending on the medical activity. For example, in the specific case of dental units, sanitised water is supplied to fill patient-use glasses, to rinse the cuspidor bowl or to spray instruments/handpieces. Water is then suitably sanitised upstream of the dental unit and downstream of the water supply network in order to eliminate any bacterial contamination (such as Escherichia coli and Legionella) that may be present in the water supply network and which can be particularly harmful if carried into the water circuit of the medical device. For this purpose, standards have been defined (e.g., UNI EN ISO 7494- 2:2015) specifying the type of water load connected to the water supply network.

In accordance with a first known solution, water collection tanks connected to the water supply network and capable of separating the supplying pipe of the water supply network from the containment basin are provided.

In other words, in this solution a supply is provided by gravity from the outlet pipe of the water supply network, determining a physical detachment between the pipes of the water supply network and the tank in which the water is collected.

The tank is in turn connected to the dental unit (or other medical device) by means of pumps served by solenoid valves to activate and adjust the load and pressure.

This known technique, while defining a physical decoupling between the water supply network and the dental unit delivery source, is nevertheless subject to bacterial diffusion that can proliferate directly inside the tank.

In fact, in this case water can remain inside the tank for an indefinite and sometimes prolonged period of time, resulting in the formation of bacterial charges. The lack of a direct sanitization intervention in the tank, therefore, makes it necessary to constantly empty the tank itself, in order to refill it with water from the water supply network.

Consequently, there are considerable drawbacks in terms of water consumption as well as maintenance resulting from periodic operations for cleaning and washing the tank and the passageways that carry the water to the dental unit.

In order to solve the above mentioned drawbacks, further known sanitising solutions are implemented, which involve the addition of hydrogen peroxide inside the tank.

In particular, such a solution involves the addition of predefined percentages of hydrogen peroxide, also known as oxygenated water (H202), which is mixed with the water inside the tank.

Thereby, oxygenated water sanitises the water contained in the tank and in the entire dental unit water circuit, eliminating the proliferation of bacteria and ensuring that the patient is free from any infections caused by the presence of pathogenic components in the water. However, this solution also has significant drawbacks and application limitations.

Firstly, oxygenated water, despite being capable of sanitising water, can have harmful effects on the body if delivered in high concentrations or in large quantities, also bearing in mind that water in the dental field is subject to being ingested. In addition, the use of oxygenated water can cause allergic reactions in some people.

A further major drawback arises from the periodic need to manually supply oxygenated water into the tank. Such an operation is subject to human error in dosing the optimal amounts of oxygenated water. In this context, automatic dosing systems are also known picking up the necessary amounts of oxygenated water directly from a bottle. However, even in this situation the operator must still periodically refill the full bottles to ensure the presence of a water disinfecting solution at all times.

In addition, the cost of consumables (oxygenated water), which must be frequently supplied to dental units, must be taken into account, with the consequent disadvantages in economic terms.

Object of the invention

In this context, the object of the present invention is to make available equipment and a management and treatment method of water supplied to the medical devices, in particular to dental units, able to solve the above- mentioned drawbacks and able to meet the requirements provided in the UNI EN ISO 7494-2:2015 standard.

In particular, the object of the present invention is to implement equipment which is structurally simple, reliable and low cost, able to comply with the regulations in force in terms of sanitization values of the water supplied to medical devices and in particular to dental units.

More particularly, the object of the present invention is to make available equipment and a related operating method, which is able to sanitize the water upstream of the dental unit or before the direct pick-up, continuously and efficiently, eliminating any bacterial proliferation inside the water circuit of the dental unit.

Still, an object of the present invention is to make available equipment and a related method which is capable of sanitising water without having to add and dose any substance to be mixed with the water.

Finally, one object of the present invention is to make available equipment and a method for sanitising water that is easy to use, fully automated, and capable of significantly lowering any maintenance operations.

The specified technical task and the specified objects are substantially achieved by equipment and a method for treating water supplied to medical devices, in particular to dental units, comprising the technical features set forth in one or more of the enclosed claims.

According to the present invention, equipment for treating water supplied to medical devices, in particular to dental units, is described, comprising: a first tank for collecting water from a water supply network, the tank having a water inlet conduit connectable to a water supply network and advantageously configured to supply the water inside the tank by gravity so as to define a physical detachment between the water in the tank and said inlet conduit.

The equipment includes at least a conduit for picking up the water contained in the tank, connectable to at least an outlet, typically a dental unit, and having a pump for supplying a predefined amount of water to said outlet. Advantageously, at least one level sensor associated with said first tank detects a minimum level and a maximum level of water in said first tank. The distance between the first and second level defines the amount of water that can be supplied to the outlet without having to refill the tank.

Advantageously, an ozone generator is provided to ozonate the water contained in the first tank. The ozone generator performs an antimicrobial action inside the water making it always properly sanitised and ready to be used in the medical field. According to the present invention, there is also described a method for treating water supplied to medical devices, in particular to dental units, comprising the steps of:

- filling a first tank with water from a water supply network;

- detecting a minimum and a maximum level of water being contained in the tank;

- picking up a predetermined amount of water from the first tank and supplying said water to at least an outlet; and

- sanitising the water inside the first tank prior to the step of picking up a predefined amount of water.

Advantageously, the step of sanitising water comprises the step of ozonating water inside the tank by introducing said ozone (by means of a whirlpool system) in an area of the first tank close to a bottom wall of the first tank itself and below said minimum water level.

The step of sanitising is carried out at the same time as the filling of the first tank and/or at regular intervals.

Further features and advantages of the present invention will appear more clearly from the indicative, and therefore non-limiting, description of a preferred but not exclusive embodiment of equipment and a method for treating water supplied to medical devices, in particular to dental units, as illustrated in the accompanying drawings.

Brief description of the drawings

Figure 1 shows a schematic and side elevation view of the equipment according to the present invention.

Figure 2 shows a perspective view and with some parts removed to better illustrate the other components included in the present invention.

Detailed description of preferred embodiments of the invention

With reference to the appended figures, reference numeral 1 globally denotes equipment for treating water supplied to medical devices, in particular to dental units.

It should be specified that, as indicated above, the present invention is used to comply with the requirements provided in the UNI EN ISO 7494- 2:2015 standard. Furthermore, the invention finds specific application in dental units where there are a plurality of outlets using sanitised water for dental handpieces suitable for delivering nebulised water or for water delivery systems for rinsing basins. However, the present invention can be used for any medical system or device provided with one or more water delivery outlets for medical/surgical treatments and intended to come into contact with the patient.

As it is illustrated in the accompanying figures, equipment 1 includes a first tank 2 for collecting water from a water supply network.

The tank 2, which may have any shape and size according to specific applications, has a bottom wall 3 and a top wall 4 opposite to the bottom wall 5, and provided with a water inlet conduit 5. The conduit 5 is in turn connectable to the water supply network, for example a domestic network, and is configured to supply water by gravity into the tank 2.

The water inlet conduit 5 has a delivery nozzle 6 arranged inside the tank and configured to remain always spaced apart from the free water surface, i.e., from the water contained in the tank 2 even when the tank is filled to the maximum level.

For this purpose, the nozzle 6 is always spaced apart of at least 2.5 cm from the maximum filling level of the tank 2. Advantageously, a condition of physical detachment between the dispensing nozzle 6 directly connected to the water supply network and the water contained inside the tank 2 is always configured. Thereby possible contacts with the water supply network that could contaminate the water contained in the tank and intended for medical use are avoided. The equipment 1 further comprises at least one conduit 7 for picking up the water contained in the tank 2, suitably connectable to at least one outlet (not described in detail and not illustrated as not forming part of the present invention). A supply pump 8 necessary to recharge the pressurized tank and to give a minimum pressure as required by the said outlet is connected to this conduit 7.

More particularly, the conduit 7 for picking up the water contained in the tank 2 is connected to a pressurized tank 10 and a pressure switch 9 arranged downstream of the pump 8; this pressure switch is adjusted to determine an outlet pressure value. The pressure switch 9 is operatively associated with pump 8 to determine, in the event of a change in the pressure value, the activation of pump 8 itself consequently picking up water from the tank 2 and supplying water to the outlet.

In other words, the pressure switch 9 detects a preset pressure value present inside the water circuit of the outlet, which in the case of dental units is typically 2 bars. When the outlet requires water, e.g., when the handpieces are activated or when rinsing water is required in the cuspidor bowl, a pressure drop occurs in the dental unit water circuit, which is detected by the pressure switch 9 and which consequently activates the pump 8.

When the outlet no longer requires water, the pressure value inside the water circuit is restored to the preset value. In this case, the pressure switch 9 detects such preset pressure value and switches off the pump 8, thus interrupting the water supply.

Advantageously, the pick-up conduit 7 further comprises a second pressurized tank 10 arranged downstream of the pump 8 and upstream of the pressure switch 9. Also the second tank 10 can have any shape and size according to the specific needs and the water flow rate to be delivered to the outlet.

Such second tank 10 is configured to pick-up a stock of water directly inside the pick-up conduit 7 and intended to be supplied to the outlet in case the pressure drop is insufficient. This water stock is able to meet the demand of the outlet immediately, thus providing continuity in delivering water to the outlet even with low pressure drops.

The first tank 2 further comprises at least one level sensor system 11 capable of detecting a minimum level L1 and a maximum level L2 of water in the first tank 2.

In greater detail, the level sensor 11 includes a first float 12 switchable between an activation condition in which it detects the minimum level L1 and a deactivation condition in which it does not detect the minimum level L2, and a second float 13 also switchable between an activation condition in which it detects the maximum level L2 and a deactivation condition in which it does not detect the maximum level L2.

As it is better illustrated schematically in figure 1, the first float 12 is close to and spaced apart from the bottom wall 3 while the second float 13 is interposed between the first float 12 and the top wall 4 of the tank 2.

The distance between the maximum level L2 and the minimum level L1 defines the amount of available water that can be delivered to the outlet, while the water below the minimum level L1 constitutes a stock, which is also available to the outlet in case of high demand.

For exemplary, and therefore not limiting purposes, the distance between the minimum level L1 and the maximum level L2 can be such as to contain 0.50 cl of water and the distance between the bottom wall 3 and the minimum level L1 can be such as to contain 0.25 cl of water. In this situation, you would have the entirety of 0.75 cl of water available inside the first tank 2.

The two floats 12, 13 are also operatively connected to a solenoid valve associated with the inlet conduit 5. The solenoid valve activates the water delivery in the deactivation condition of the first float 12, i.e. in the condition in which the water falls below the minimum level L1.

The solenoid valve deactivates the water delivery from the inlet conduit 5 in the condition of activation of the second float 13, i.e., when the water reaches the maximum level L2.

Thereby, the tank 2 is automatically filled with water from the water supply network (delivered by gravity from nozzle 6) by detecting through the first float 12 an amount of water lower than the minimum level L1 (less than one litre) and interrupting such delivery in the condition of filling the tank 2 to the maximum level (reaching 0.75 litres).

Preferably, a discharge conduit 14 configured to drain water out of the tank 2 in an overflow condition resulting from a malfunction of the second float 13 or the solenoid valve in the closing step is also provided.

Said discharge conduit 14 turns out to be arranged between the second float 13 and the top wall 4, in particular just above the second float 13, in such a way as to avoid flooding and leakage of water given by the overfilling of the tank 2. In this way, it is also ensured that the physical detachment between the nozzle 6 and the free surface of the water contained in the tank 2 is maintained.

In accordance with a main feature of the present invention, the equipment 1 further comprises an ozone generator 15 operatively engaged inside the first tank 2 to ozonate the water contained in the first tank 2 itself.

For exemplary, and therefore not limiting purposes, the ozone generator can be of the corona discharge type, equipped with a pulse device and having a maximum concentration capacity of 300 Mg/h.

The ozone generator 15 has a pipe 16 that at least partially extends inside the first tank 2. In particular, the pipe 16 has a first end 16a arranged inside the first tank 2 at the bottom wall 3, and a second end 16b arranged outside the first tank 2.

The ozone generator 15 also has a bubbler filter 17 associated with the first end 16a of the pipe 16 to distribute the ozone near the bottom wall 3 and in particular below the minimum level L1.

The ozone generator 15 further has an ozone generating body 18 associated with the second end 16b of the pipe 16 which appears to be arranged outside the tank 2 and preferably associated with a box frame containing the entire equipment 1 (Figure 2).

The ozone generator 15 further preferably includes an electronic ozone delivery activation system operatively associated with the first 12 and second 13 floats.

In particular, the electronic system activates the delivery of ozone from the bubbler filter 17 in the deactivation condition of the first float 12, that is, in the condition in which the water is below the minimum level L1. The ozone delivery is then deactivated in the condition of activation of the second float 13, i.e. , in the condition in which the water inside the tank reaches the maximum level L2.

Consequently, water ionization inside the tank 2 is ensured from the moment the filling is activated (amount of water below the minimum level L1) until the water reaches full filling (maximum level L2). In other words, filling and ozonating operations take place simultaneously in order to ensure sanitised water inside the tank 2 at all times.

The present invention which has been so far described mainly structurally, further relates to a method for sanitising water supplied to medical devices, in particular to dental units.

The method comprises the following steps:

- filling the first tank 2 with water from the water supply network;

- detecting the minimum level L1 and the maximum level L2 of water being contained in tank 2;

- sanitising the water inside the first tank 2; and then

- picking up a predefined amount of water from the first tank 2 and supplying the sanitised water to at least an outlet.

The step of sanitising water comprises the step of ozonating the water inside the tank 2 by introducing ozone into an area of the first tank 2 close to the bottom wall 3 of the first tank 2 itself and below the minimum level L1 of the water.

The step of filling the first tank 2 is implemented by supplying by gravity and from the top 4 of the first tank 2 the water from the water supply network and towards the bottom wall 3 of the tank 2.

Thereby, as described above, the physical detachment of the supply pipes from the water supply network is maintained from the volume of water contained in tank 2.

The step of detecting the minimum level L1 and the maximum level L2 of the water being contained in the tank 2 is implemented by activating the first float 12 arranged close to the bottom wall 3 and activating the second float 13 arranged between the first float 12 and the top wall 4 of the tank 2. The step of detecting the minimum level L1 and the maximum level L2 of water in the first tank 2 is implemented both to determine the possible filling of the tank 2 and to sanitize the water input into the tank 2.

In fact, the phase of filling the tank 2 is implemented by the solenoid valve that is activated by the first float 12 in the respective deactivated condition (in which it does not detect the minimum level L1 of water).

The step of filling is therefore always interrupted by the solenoid valve which is deactivated by the second float 13 in the respective activated condition (in which it detects the maximum level L2).

Similarly, the step of sanitising by ozonating the water is implemented by the ozone generator 15 activated by the first float 12 in the respective deactivated condition. The ozone generator 15 is deactivated by the second float 13 in the respective activated condition in which it detects the maximum level L2.

Therefore, the step of filling the first tank and the step of sanitising the water in the tank are implemented simultaneously.

The step of ozonating the water inside the tank 2 is implemented by generating ozone outside the tank 2 and supplying ozone through the pipe 16 from the bubbler filter 17 arranged between the first float 12 and the bottom wall 3 of the tank 2.

Therefore, sanitisation is always done from the bottom in order to ensure proper sanitisation of the entire volume of water contained in the tank 2.

In addition, the step of ozonating the water inside the tank 2 can be implemented at predefined intervals in time to keep the water in the tank 2 always sanitised and regardless of the filling step. Thereby, if there is no demand for water from the outlet for a prolonged period, stagnation of the water inside the tank with the consequent proliferation of bacteria is always avoided.

For example, in the case of dental units, in the period from the last use of the day and the first use of the following day, the water contained and retained in the tank for a few hours may degenerate and compromise the sanitisation characteristics.

In this situation, periodically ozonating, for example during the night and before the first use of the day, ensures in any case the correct sanitary conditions for using water.

The step of picking up a predetermined amount of water contained in the first tank 2 is implemented by detecting with the pressure switch 9 the pressure value of the outlet which is lower than the predetermined pressure value. The pressure switch 9 activates the pump 8 for picking up water from the first tank 2 to deliver water to the outlet and re-establish the predetermined pressure value.

Advantageously, there is also provided a step of supplying water contained in the second pressurized tank 10 arranged downstream of the pump 8. This step is implemented in case the pressure drop is not sufficient to activate the pump 8.

Advantageously, the ozonization process effectively sanitises the water contained in the tank 2 and intended to be supplied to the outlets. Therefore, the equipment 1 always guarantees the sufficient amount of water and the correct sanitisation condition derived from the action of ozone, which is known to have an antimicrobial effect.

The automatic activation of filling the tank 2 and ozonization also has the considerable advantage of eliminating all manual maintenance and sanitization operations with consequent advantages in terms of ease of use and overall costs. In this regard, it should be noted that the process of generating and delivering ozone eliminates any possible process of adding additives into the water and any possible consumable, making the equipment long-lasting, and maintenance-free.

A further advantage derives from the versatility of the equipment 1 usable for any medical device and connectable to any number of outlets. In this context, by connecting the equipment to the water supply network and electricity grid, it can supply water to one or more dental units with any number of outlets.

Claims

1. Equipment for treating water supplied to medical devices, in particular to dental units, comprising:

- a first tank (2) for collecting water from a water supply network, said tank (2) having a water inlet conduit (5) connectable to said water supply network and configured to supply water by gravity into the tank (2);

- at least one conduit (7) for picking up the water contained in the tank (2), connectable to at least an outlet and having a pump (8) for supplying a predefined amount of water to said outlet;

- at least a level sensor (11) associated with said first tank (2) for detecting a minimum level (L1) and a maximum level (L2) of water in said first tank (11); characterized in that it comprises an ozone generator (15), operatively engaged inside the first tank (2) to ozonate the water contained in the first tank (2).

2. Equipment according to the preceding claim, characterized in that said ozone generator (15) comprises: a pipe (16) at least partially extending into the first tank (2); a bubbler filter (17) associated with a first end (16a) of the ozone outlet pipe (16), said filter (17) being arranged at a bottom wall (3) of said tank (2); and an ozone generating body associated with a second end (16b) of the ozone inlet pipe (16) arranged outside said tank (2).

3. Equipment according to the preceding claims, characterized in that said inlet conduit (5) is associated with a top wall (4) of the first tank (2) opposite to a bottom wall (3) of the tank (2); said inlet conduit (5) having a nozzle (6) for delivering water from the water supply network spaced apart from the maximum level (L2) of water contained in the first tank (2).

4. Equipment according to the preceding claim, characterized in that said distance between the water delivery nozzle (6) and the maximum level (L2) of water in the tank (2) is greater than or equal to 3 cm.

5. Equipment according to any one of the preceding claims, characterized in that said conduit (7) for picking up the water contained in the tank (2) further comprises a pressure switch (9) arranged downstream of said pump (8) for determining an outlet pressure value and activating the pump (8) in case of variation of said pressure value.

6. Equipment according to any one of the preceding claims, characterized in that said conduit (7) picking up the water contained in the first tank (2) further comprises a second pressurized tank (10) arranged downstream of the pump (8) and configured to collect a stock of water to be supplied to the outlet.

7. Equipment according to any one of the preceding claims, characterised in that said level sensor (11) comprises a first float (12) switchable between an activation condition wherein it detects said minimum level (L1) and a deactivation condition wherein it does not detect the minimum level (L1), and a second float (13) interposed between the first float (12) and a top wall (4) of the tank (2) and switchable between an activation condition wherein it detects the maximum level (L2) and a deactivation condition wherein it does not detect said maximum level (L2).

8. Equipment according to the preceding claim, characterized in that said inlet conduit (5) comprises a solenoid valve operatively engaged to said floats (12, 13) to activate the water delivery in the deactivation condition of the first float (12) and to deactivate the water delivery in the activation condition of the second float (13).

9. Equipment according to the preceding claim, characterized in that said ozone generator (15) comprises an electronic ozone delivery system associated to said first and second floats (12, 13) for activating the ozone delivery from the bubbler filter (17) in the deactivation condition of the first float (12) and for deactivating the ozone delivery in the activation condition of the second float (13).

10. Method for treating water supplied to medical devices, particularly to dental units, comprising the steps of:

- filling a first tank (2) with water from a water supply network;

- detecting a minimum level (L1) and a maximum level (L2) of water being contained in the tank (2);

- picking up a predetermined amount of water from the first tank (2) and supplying said water to at least an outlet; and

- sanitising the water inside the first tank (2) prior to the step of picking up a predefined amount of water; characterized in that said step of sanitising the water comprises the step of ozonating the water inside the tank (2) by introducing said ozone into an area of the first tank (2) close to a bottom wall (3) of the first tank (2) itself and below said minimum level (L1) of the water.

11. Method according to the preceding claim, characterized in that said step of filling the first tank (2) is implemented by supplying by gravity and from the top of the first tank (2) the water coming from the water supply network towards the bottom wall (3) of the tank (2).

12. Method according to claim 10, characterized in that said step of detecting a minimum level (L1) and a maximum level (L2) of water being contained in the tank (2) is implemented by activating a first float (12) arranged inside the tank (2) and close to the bottom wall (3) and activating a second float (13) arranged in the tank (2) between the first float (12) and a top wall (4) of the tank (2) itself.

13. Method according to the preceding claim, characterized in that said step of filling the first tank (2) with water coming from a water supply network is implemented by a solenoid valve which is activated by the first float (12) in the respective condition and deactivated when said minimum level (L1) is not detected; said step of filling is interrupted by the solenoid valve which is deactivated by the second float (13) in the respective activated condition in which said maximum level (L2) is detected.

14. Method according to claim 12 or 13, characterized in that said step of sanitising by ozonating the water is implemented by an ozone generator (15) activated by the first float (12) in the respective deactivated condition wherein it does not detect said minimum level (L1); said ozone generator (15) being deactivated by the second float (13) in the respective activated condition wherein it detects said maximum level (L2).

15. Method according to the preceding claim, characterized in that said step of filling the first tank (2) and said step of sanitising the water in the tank (2) are implemented concurrently.

16. Method according to claim 14, characterized in that said step of ozonating the water inside the tank (2) is implemented by generating ozone outside the tank (2), supplying the ozone through a pipe (16) passing inside the tank (2) and delivering the ozone through a bubbler filter (17) arranged between the first float (12) and the bottom wall (3) of the tank.

17. Method according to claim 10, characterized in that said step of picking up a predefined amount of water contained in the first tank (2) is implemented by detecting with a pressure switch (9) a pressure value of the outlet that is lower than a predetermined pressure value; said pressure switch (9) activating a pump (8) for picking up water from the first tank (2) to deliver the picked-up water to the outlet and re-establish said predetermined pressure value.

18. Method according to the preceding claim, characterized in that said step of supplying water to the outlet is implemented by means of a second pressurized tank (10) arranged downstream of the pump (8); said water being supplied to the outlet by said second tank (10) at a predetermined pressure value.

19. Method according to the preceding claim, characterized in that it further comprises, following the step of supplying water to the outlet, the step of filling the second tank (10) by picking up water from the first tank (2) by means of said pump (8).

20. Method according to claim 10, characterized in that said step of ozonating the water inside the tank (2) is implemented at predefined intervals over time to keep the water in the tank (2) always sanitised.