JPH06141995A - Method and device for purification of hot water in bathtub - Google Patents

Abstract

PURPOSE:To provide a bathtub water purifying device and establish a purifying method, with which reverse wash of a filtrating material can be done effectively and which is structured simply and at a low cost. CONSTITUTION:With a 7-port selector valve 5, seven hot water flowing pipes are connected, i.e., sucking/spouting pipes 3, 12 for a bathtub 1, tank outflow/inflow pipes 7, 8 for a filtration tank 6, pump outflow/inflow pipes 10, 11 for a circulation pump 9, and a hot water discharging pipe 13, and with switching of this selector valve, three hot water circulating paths are formed, for purification with the hot water flowing in the regular direction, reverse wash with the water flowing in the opposite direction, and as a regularly directed closed loop with the flow to the bathtub shut, and when the reverse wash is finished, return is made to the purification upon making closed loop circulation. Accordingly switching of the circulation path can be done easily using a simple and low cost selector value and reverse wash of the filtration material can be made effectively, and owing to the closed loop circulation, contaminants separated from the filtration member at the time of reverse wash do not contaminate the bathtub hot water when return is made from the reverse wash to purification, so that the hot water can be kept clean at all times.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bathtub device, and in particular, to properly clean a filtration tank filled with a filter medium such as activated stone or activated carbon to effectively filter dirt in hot water and keep the hot water constantly clean. The present invention relates to a device for purifying bath water having a backwash function.

[0002]

2. Description of the Related Art Recently, cleaning of bath water by pumping hot water in a bathtub with a circulation pump and forcibly circulating it through a circulation path provided with various types of cleaning treatment equipment and ejecting the purified hot water again into the bathtub The device was developed.

This bath water purifying device includes a circulation pump for circulating the hot water, a pre-filter provided at the hot water inlet of the hot water pipe for filtering large dirt, and the capacity of the filtering material while filtering dirt. There is provided a cleaning tank such as a filtration tank filled with a porous granular filter medium for performing water treatment according to the above, an ozone sterilizer for sterilization, and a heater for keeping hot water at an appropriate temperature.

In the filtration tank, dirt is removed by ion exchange, and at the same time, activated stone such as barley stone that elutes and activates minerals, activated carbon that adsorbs and removes dirt, and dirt is adsorbed and adsorbed at the same time. Porous granular materials having various water treatment capacities such as zeolite, which are removed by means of the above method, are filled individually or in combination to form a filtration layer.

Therefore, the filtration tank is, as described above,
Not only the filtration capacity of the filtration layer, but also the water treatment capacity according to the capacity of the filled filter material is effective in cleaning the bath water.

With the development of the cleaning device as described above, it becomes possible to enjoy comfortable bathing with hot water of a suitable temperature at any time for 24 hours without changing the hot water.

When such a cleaning device is continuously operated, the filter medium filled in the filter tank becomes dirty and the filter layer is clogged, the circulating amount of hot water is reduced, and the cleaning ability is deteriorated.

Therefore, when the filter layer is clogged,
Since the filter medium forming the filter layer is not always cheap and cannot be replaced frequently, the filter medium is taken out of the filtration tank and washed.

Further, cleaning the filter medium is troublesome and at the same time not so preferred for dirty work. Therefore, in order to automatically wash the filter medium without removing it from the filter tank, it is necessary to clean the filter layer with hot water. A lot of devices equipped with a so-called backwashing device for washing the filter medium by flowing in the opposite direction have been developed.

[0010]

However, there are two major problems in cleaning the filter medium using the conventional backwashing device: the pipe switching device and the contamination of the bath water immediately after the backwashing.

First, in order to perform backwashing, the flow direction of hot water is reversed to that in the case of cleaning, and two-way switching is performed in order to discharge the washed hot water to the outside of the bathtub through the hot water discharge pipe. Solenoid valves that perform the above must be provided at multiple locations.

However, when a plurality of solenoid valves are provided in the hot water flow passage, the control device for switching the pipeline is complicated and expensive, and at the same time, the solenoid valve is liable to be damaged due to dirt in the hot water. However, if a plurality of these devices are arranged, the device is likely to break down.

Next, when backwashing is performed, most of the dirt attached to the filter material is separated from the filter material and discharged through the hot water discharge pipe, but a part of the dirt left after being separated from the filter material but not discharged is left. Immediately after the part finishes backwashing and starts cleaning, it may flow into the bathtub and pollute the hot water in the bathtub.

The present invention solves the above-mentioned drawbacks of the prior art, utilizes a simple and inexpensive device that does not cause a failure, and can effectively perform backwashing, and even in the cleaning immediately after backwashing, the bathtub can be cleaned. It is an object of the present invention to provide a bathtub hot water cleaning device and a cleaning method in which dirt does not flow into the bathtub.

[0015]

[Means for Solving the Problem] That is, according to the present invention, the hot water in the bathtub is pumped up by a circulation pump through a hot water suction pipe, the dirt is filtered by a filter tank, and then returned to the bathtub again through a hot water pipe so that the hot water is constantly fed. In a bath water purifying device for keeping clean, a suction pipe and a spout pipe for sucking hot water into and out of a bath, a tank inflow pipe and a tank outflow pipe for flowing hot water into and out of a filtration tank, and a circulation pump A 7-port switching valve connected to one end of seven hot water flow pipes of a pump inflow pipe and an outflow pipe for inflowing and outflowing hot water and a hot water discharge pipe for discharging the hot water out of the bathtub; and a check valve for the hot water suction pipe. Is a bathtub hot water purifying device, and the switching valve is
A cylindrical valve case having seven connection ports for each hot water distribution pipe provided on the upper surface and an open lower surface, and a plurality of cylindrical valve cases rotatably fitted in the valve case and connected to the connection ports to connect the connection ports to each other. Rotatably supporting a valve body having a drive shaft and a hot water flow passage and a drive shaft connected to the hot water flow passage provided in the valve body and connecting the hot water flow passages to each other. A bath water purifying device having the above-mentioned configuration, characterized in that it comprises a valve lid which is provided with a bearing hole and closes an opening on the lower surface of the valve case. Further, the switching valve allows hot water to flow as the valve body rotates. The connection port of the pipe and the hot water passage are selectively connected to each other, and the hot water pipe, the filtration tank, the circulation pump, and the cleaning circulation path in which hot water circulates in the order of the hot water pipe, the hot water pipe, the circulation pump, the filtration tank, and the drainage pipe. Hot water circulates in the order of the hot water pipe, the backwash circulation path, the filtration tank, and the circulation pump. The bathtub hot water purifying device having the above-mentioned configuration, characterized in that the pipe lines are switched so as to form three closed-loop hot water circulation routes, and the hot water is circulated in the reverse direction in the backwash circulation route. After cleaning the dirt adhering to the filter medium, the closed loop circulation path that blocks the circulation of the hot water to the bath tub is circulated in the forward direction for a predetermined time and then switched to the forward purification circulation path. This is the cleaning method.

[0016]

The present invention is configured as described above, and by appropriately rotating the valve body of the switching valve, the hot water circulation path is cleaned in the forward direction, backwashed in the reverse direction, and the hot water is circulated to the bathtub. It can be easily switched to three closed loops that shut off and flow hot water in the forward direction.

Furthermore, since the structure of the switching valve is simple, it is easy to manufacture and inexpensive, and there is almost no risk of failure due to dirt and the valve is provided with individual connection ports for each hot water distribution pipe. Since the hot water flow passage is provided for connecting the adjacent and opposite connection ports to each other, the piping is extremely simple.

Before the backwashing is completed and the pipe line is switched to the cleaning, the hot water is blocked from flowing into the bathtub and the hot water is circulated in a closed loop so that the hot water is circulated in the forward direction. The dirt that has not been separated and discharged will adhere to the filter medium again during this circulation, so there is no concern that dirt enters the bath immediately after cleaning is started.

[0019]

Embodiments of the present invention will now be described with reference to the drawings.

FIG. 1 is a piping diagram showing the structure of the apparatus of the present invention, in which 1 is a bathtub, 2 is hot water, 3 is a hot water suction pipe for sucking hot water 2 from the bathtub, 4 is hot water in the direction opposite to the hot water pipe. Check valve for preventing the flow of water, 5 is a 7-port switching valve with independent connection ports for 7 hot water flow pipes, 6 is a filtration tank filled with a filter medium such as activated carbon or boiled stone, and 7 is a filtration tank 6 A tank inflow pipe connected to the upper side surface of the tank through which hot water flows in, a tank outflow pipe 8 connected to a tank bottom surface through which filtered hot water flows out of the filtration tank 6, and a circulation pump 9 for forcedly circulating hot water, 10 is a pump inflow pipe for inflowing hot water into the circulation pump 9, 11 is a pump outflow pipe for outflowing hot water from the circulation pump 9, 12 is a spouting pipe for re-injecting the hot water after the cleaning treatment into the bathtub 1, and 13 is the reverse. Drain hot water for washing out of bathtub 1 when washing Exhaust is a hot water pipe.

One end of the seven hot water flow pipes, which are the hot water suction pipe 3, the tank outflow and outflow pipes 7 and 8, the pump outflow and outflow pipes 10 and 11, the spouted hot water pipe 12, and the hot water discharge pipe 13, which form a hot water circulation path, are provided with a switching valve. 5
7 are connected to each of the seven connection ports as shown in FIG.

Next, the state in which a circulation path for hot water is formed will be described. FIG. 2 shows a case where hot water is cleaned. In this case, the switching valve 5 connects the hot water suction pipe 3 and the tank inflow pipe 7. In the hot water flow passage 14, the tank outflow pipe 8 and the pump inflow pipe 10 are connected by the hot water flow passage 15, and the pump outflow pipe 11 and the hot water discharge pipe 12 are connected by the hot water flow passage 16, respectively. As shown by the arrow, the hot water is closed and switched to a forward flow from the hot water suction pipe 3 to the hot water pipe 12 after flowing from the top to the bottom in the filtration tank 6.

When the circulation pump 9 is operated in this state, the hot water 2 in the bathtub 1 is sucked up from the hot water suction pipe 3, and the flow of the hot water is in the forward direction, so the check valve 4 is opened and the switching valve 5 and the tank inflow pipe. It flows into the filtration tank 6 from above via 7.

The hot water that has entered the filtration tank 6 flows downward while the dirt is filtered by the filled filter material and at the same time the activation stones are activated and the like, and the tank outflow pipe 8,
Switching valve 5, pump inflow pipe 10, circulation pump 9, switching valve 5
After that, the molten metal is returned from the spout tube 12 to the bathtub 1 again, and the circulation cleans the hot water.

Next, the case where the hot water is cleaned for a predetermined time and the filter medium filled in the filter tank 6 becomes clogged with dirt and backwashing is performed to remove the dirt will be described with reference to FIG. .

In this case, the switching valve 5 has a hot water suction pipe 3 and a pump inflow pipe 10 as a hot water flow passage 17, a pump outflow pipe 11 and a tank outflow pipe 8 as a hot water flow pipe 18, and a tank inflow pipe 7 and a drainage pipe 7. The hot water pipes 13 are connected to each other by hot water flow pipes 19, and the direction of the hot water discharge pipe 13 is opened and at the same time the direction of the hot water pipe 12 is closed, so that the hot water flows from the hot water suction pipe 3 to the filtration tank 6 from below as shown by the arrow. After flowing upward, it is switched so as to flow toward the hot water discharge pipe 13 and in the opposite direction.

When the circulation pump 9 is operated in this state, the hot water 2 in the bathtub 1 is sucked up from the hot water pipe 3 and the flow of the hot water is in the forward direction, so the check valve 4 is opened and the switching valve 5 and It enters the circulation pump via the pump inlet pipe 10.

The hot water that has entered the circulation pump 9 is the pump outflow pipe 1.
1, the changeover valve 5 and the tank outflow pipe 8 enter the filtration tank 6, and the inside of the filtration tank 6 flows from the bottom to the top in the reverse direction to remove the dirt adhering to the filter medium for backwashing.

The hot water obtained by backwashing the filtration tank 6 is discharged from the hot water discharge pipe 13 through the tank inflow pipe 7 and the switching valve 5, and if this is continued for a predetermined time, the filter medium filled in the filtration tank 6 is not clogged. The forward flow again allows cleaning.

FIG. 4 shows the case of a closed loop in which the hot water is circulated in the forward direction in a state where the flow of the hot water to the bathtub 1 is cut off. In this case, the switching valve 5 causes the pump outflow in the forward flow. The pipe 11 is made to communicate with the tank inflow pipe 7 through the hot water flow passage 20 which is connected to the hot water flow passage 14 which connects the hot water suction pipe 3 and the tank inflow pipe 7, and the hot water flows into the bathtub 1 as shown by the arrow. It is switched so as to circulate in the forward direction in a state where the circulation of the is blocked.

When the circulation pump 9 is operated in this state,
The hot water is cut off from the communication between the pump outflow pipe 11 and the spout pipe 12, and at the same time, the flow of the hot water to the suction pipe 3 and the spout pipe 12 is completely cut off by the action of the check valve 4 of the suction pipe 3 for filtration. It circulates forward between the tank 6 and the circulation pump 9.

When the circulation of the hot water is continued for a predetermined time, the dirt which has been separated from the filter medium of the filtration tank 6 by the back washing but not discharged from the hot water discharge pipe 13 is attached to the filter medium again, and then the circulation of the cleaning process is carried out. No dirt is brought into the bathtub 1 when returning to the road.

Next, the structure of the switching valve 5 for switching the circulation path of the hot water as described above will be described. The positional relationship between the parts constituting the switching valve is such that the switching valve forms the circulation path of the hot water for cleaning. The description will be given based on the state of switching to form.

FIG. 5 is an exploded perspective view of the switching valve 5.
Is a cylindrical valve case with an open bottom surface,
Seven connection ports 22 and 2 for connecting each of the hot water distribution pipes of the book
3, 24, 25, 26, 27, 28 are arranged at equal intervals at eight positions on the circumference slightly inward of the outer circumference with one position as a defect position.

Reference numeral 29 denotes a disc-shaped valve body which is rotatably fitted in the valve case 21.
In order to form a hot water passage for circulating hot water between the connection ports on the circumference corresponding to the connection ports 22 to 28 on the contact surface of the valve case 21, the adjacent mouth connection hot water flow grooves 30, 31, 3 are provided.
2 and opposing hot water circulation holes 33 and 34 are provided.

The adjacent mouth connection hot water flow grooves 30, 31, 32 are
Connections are 23 and 24, 25 and 26, 27 and 28, and 6 connection ports except one of the 7 connection ports are connected to each other by adjacent connection ports. And is formed as a blind long groove that does not reach the back surface.

The opposing hot water circulation holes 33 and 34 are provided as through holes reaching the back surface so that the hot water from the connection ports at the opposing positions can flow into the opposing port connection hot water circulation groove provided in the valve lid described later. 33 is one of the eight equally divided positions of the circumference where the seven connection ports 22 to 28 of the valve case 21 are arranged.
Opposite hot water circulation holes 34 are provided at positions corresponding to the three defective positions, and at positions facing the holes 33.

Reference numeral 35 is a drive shaft extending vertically downward from the center of the back surface for rotating the valve element 29.

Reference numeral 36 is a cylindrical valve lid which is fitted to the valve case 21 to which the valve element 29 is fitted and which closes the opening on the lower surface and has an open upper surface.

On the lower surface of the valve lid 36, the valve element 29 is provided at the center.
Is provided with a bearing hole 37 through which the drive shaft 35 is passed, and is a diametrical blind groove that connects the connection ports of the valve body 29 facing each other through the opposed hot water flow holes 33 and 34 as a hot water flow passage. Opposite mouth connection hot water circulation groove 38 is provided.

Next, the state in which the switching valve 5 having the above-mentioned structure is switched to form the circulation path for hot water will be described.

The state in which the switching valve 5 is switched so as to form the circulation path for cleaning the hot water is as shown in FIG. 6 as a top view (a) and a vertical sectional view (b). The connection state of the connection port and the hot water distribution pipe will be described.

The connection state of the hot water flow pipe to each connection port is as follows.
The reference numerals of the hot water flow pipes in FIG. 1 are shown in parentheses. The hot water discharge pipe 13 is provided at the connection port 22 and the tank inflow pipe 7 is provided at the connection port 23.
However, 24 is the hot water suction pipe 3, 25 is the pump inflow pipe 10
However, 26 is connected to the tank outflow pipe 8, 27 is connected to the pump outflow pipe 11, and 28 is connected to the spout pipe 12.

In such a hot water cleaning state, the valve body 2
The motor 9 is rotated by the motor 39 via the drive shaft 35, and the adjacent connection ports 23 and 24 are adjacent connection hot water flow grooves 30, and 25 and 26 are adjacent connection hot water flow grooves 31.
27 and 28 are located so as to coincide with the adjacent mouth connection hot water circulation groove 32.

As a result, as shown in the parentheses of the molten metal flow passage of FIG. 2, the adjacent inlet connection molten metal flow groove 30 adjoins the molten metal flow passage 14 which connects the hot water suction pipe 3 and the tank inflow pipe 7. The mouth connection hot water flow groove 31 connects the tank outflow pipe 8 and the pump inflow pipe 10 with the hot water flow passage 15, and the adjacent mouth connection hot water flow groove 32 connects the pump outflow pipe 11 and the hot water flow pipe 16 with each other.
To form.

Since the connection port 22 is not connected to other connection ports, the flow of hot water to the hot water discharge pipe 13 connected thereto is cut off, and at the same time, the opposite hot water flow holes 33 and 34 are formed at the opposite ports. Since there is no hot water flow passage formed to connect the connection ports that are not aligned with the connection hot water flow groove 38, as shown in FIG.
A hot water circulation path for cleaning is formed as shown in FIG.

Next, a state in which the valve body 29 is rotated to form a hot water circulation path for backwashing will be described with reference to FIG.

In this state, the valve element 29 is located rotated by 45 ° in the clockwise direction from the cleaned state, and the adjacent connection ports 22 and 23 are adjacent to each other.
In addition, 24 and 25 coincide with the adjacent mouth connection hot water circulation groove 31, and 26 and 27 coincide with the adjacent mouth connection hot water circulation groove 32.

As a result, as shown in the parentheses of the molten metal flow passage in FIG. 3, the adjacent molten metal flow passage 31 adjoins the molten metal flow passage 17 connecting the hot water suction pipe 3 and the pump inflow pipe 10. The mouth connection hot water flow groove 32 connects the pump outflow pipe 11 and the tank outflow pipe 8 with the hot water flow passage 18, and the adjacent mouth connection hot water flow groove 30 connects the tank inflow pipe 7 and the hot water discharge pipe 13 with each other. 19
To form.

Further, since the connection port 28 is not connected to any other connection port, the flow of the hot water to the spout tube 12 is cut off, and at the same time, the opposite hot water flow holes 33 and 34 are aligned with the opposite port connection hot water flow groove 38. Since there is no hot water flow path connecting the opposite connection ports, a hot water circulation path for backwashing is formed as shown in FIG.

Finally, a state in which a hot water circulation path is formed for a closed loop for circulating hot water in the forward direction in a state where the hot water circulation to the bathtub is cut off will be described.

In this state, the valve body 29 is located in a state further rotated by 45 ° from the backwash state, and the adjacent connection ports 23 and 24 are adjacent to each other and the adjacent port connection hot water flow groove 31. And 25 and 26 coincide with the adjacent mouth connection hot water circulation groove 32.

Further, the opposing connection ports 23 and 27 are aligned with the opposing hot water flow holes 34 and 33, respectively, and the opposing hot water flow holes 33 and 34 are aligned with the opposing port connection hot water flow groove 38, and are further opposed to each other. The hot water flow hole 34 also coincides with the adjacent mouth connection hot water flow groove 31.

As a result, as shown in the parentheses of the molten metal flow passage in FIG. 4, the adjacent inlet connection molten metal flow groove 31 adjoins the molten metal flow passage 14 connecting the hot water suction pipe 3 and the tank inflow pipe 7. The mouth connection hot water circulation groove 32 forms the hot water flow passage 15 that connects the tank outflow pipe 8 and the pump inflow pipe 10, and the counter mouth hot water flow groove 38 is connected to the pump outflow pipe 11 via the counter hot water flow holes 33 and 34. A hot water flow passage 20 is formed to connect with the tank inflow pipe 7.

A connection port 28 to which the spout tube 12 is connected
The connection port 22 to which the hot water discharge pipe 13 is connected is not connected to other connection ports, and the flow of hot water to these pipes is cut off, and the hot water flow passage 20 connects the hot water suction pipe 3 and the tank inflow pipe 7 to each other. Since the check valve 4 provided in the hot water suction pipe 3 prevents the flow toward the bath tub 1 even if it is connected to the hot water flow passage 14 which connects the tank through the connection port 23 to which the tank inflow pipe 7 is connected, Hot water bath 1
A closed-loop circuit is formed that flows in the forward direction with the flow to the front closed.

[0056]

The present invention has the above-described structure and operation, and the dirt on the filter medium is automatically removed by backwashing at a predetermined interval, so that the effect is always obtained without spending time and money for maintenance. There is provided a bath water purifying device provided with a filtering device capable of performing effective filtration.

Moreover, after the backwashing is finished, a closed loop circulation is carried out in which the hot water is cut off in the direction of the bathtub in the forward direction, and the backwash is separated from the filter medium but remains without being discharged. Immediately after the dirt is attached to the filter medium again and the cleaning is restarted, the hot water in the bathtub is not contaminated by the remaining dirt.

The switching valve for switching the hot water circulation path used in this apparatus has a simple structure and can be easily manufactured at a low cost. At the same time, the control for switching the piping path is easy and it is unlikely to break down during operation. .

Further, since the switching valve itself has the hot water flow passage connecting the hot water flow pipes to each other and the piping can be simply performed with a very small number of pipes, the manufacture, installation, maintenance and the like of the device are easy.

[Brief description of drawings]

FIG. 1 is a piping diagram of an embodiment,

[Fig. 2] Circulation path of hot water at the time of cleaning,

[Fig. 3] Hot water circulation during backwashing,

[Fig. 4] Circulation path of hot water in closed loop,

FIG. 5 is an exploded perspective view of a switching valve,

FIG. 6 is a switching switching state of the switching valve,

FIG. 7 is a backwash switching state of the switching valve,

FIG. 8 shows a closed loop switching state of the switching valve.

[Explanation of symbols]

 1 Bathtub 2 Hot water 3 Hot water suction pipe 4 Check valve 5 Switching valve 6 Filtration tank 7 Tank inflow pipe 8 Tank outflow pipe 9 Circulating pump 10 Pump inflow pipe 11 Pump outflow pipe 12 Hot water pipe 13 Drainage water pipe 14-20 Hot water flow passage 21 Valve Case 22-28 Connection Port 29 Valve Body 30-33 Adjacent Port Connection Hot Water Flow Groove 33, 34 Opposing Hot Water Flow Hole 35 Drive Shaft 36 Valve Lid 38 Opposing Port Connection Hot Water Flow Groove

Claims (4)

[Claims] 1. Cleaning of bath water for continuously keeping the bath water clean by pumping hot water in the bathtub with a circulation pump through a hot water pipe, filtering dirt in a filtration tank, and then returning it to the bathtub again with a hot water pipe Sucking pipe and spouting pipe for sucking and ejecting hot water to and from a bathtub, tank inflow pipe and tank outflow pipe for letting hot water flow in and out of a filtration tank, and pump for letting hot water flow in and out of a circulation pump It is characterized in that a 7-port switching valve to which one end of seven hot water flow pipes of an inflow pipe, an outflow pipe, and a hot water discharge pipe discharged to the outside of the bathtub are connected, and a check valve for the hot water suction pipe are provided. Bath water purifier. 2. A switching valve, which is a cylindrical valve case in which seven connection ports for each hot water flow pipe are provided on the upper surface and the lower surface is open,
A valve body having a plurality of hot water flow passages rotatably fitted in the valve case, connected to the connection ports of the valve case and connecting the connection ports, and provided with a drive shaft, and the valve body. A cylinder with an open upper surface that is fitted to close the lower surface opening of the valve case provided with a hot water flow passage that is connected to the hot water flow passage provided and that connects the hot water flow passages and a bearing hole that rotatably supports the drive shaft The bath water cleaning device according to claim 1, wherein the device comprises a valve-like valve lid. 3. The hot water flow pipe, the filtration tank, the circulation pump, and the hot water pipe are connected in this order by the connection port of the hot water flow pipe and the hot water flow passage being selectively connected to each other as the switching valve rotates. A circulation circuit in which the water circulates in the forward direction, a hot water pipe, a circulation pump, a filtration tank, and a backwash circulation circuit in which hot water circulates in the reverse direction in the order of the drain pipe, and a circulation in the order of the filtration tank and the circulation pump to the bath. 3. The bath water purifying apparatus according to claim 1 or 2, wherein the pipes are switched so as to form three closed-loop circulating passages for circulating the hot water in the forward direction with the hot water being cut off. 4. A closed loop circuit in which hot water circulates in the forward direction after the hot water is circulated in a reverse direction in a backwash circuit to wash dirt adhering to the filter medium, and the circulation to the bath is blocked. A method for cleaning hot water in a bathtub, which comprises circulating the water for a predetermined time and then switching to a cleaning circulation path in the forward direction.