Water inlet device for a filter unit, filter unit and filter system

Abstract

The invention relates to a water inlet device for a filter unit (12), having a water inlet container (27) which delimits a water collection space (28) into which opens a water inlet opening (33) that penetrates a container wall (29) of the water inlet container (27), wherein the water inlet container (27) has, on a top side, an outflow opening (34) which is delimited by the container wall (29) and has a fastening interface (35) for a filter attachment (40) belonging to the filter unit (12).

Description

[0001] Water inlet device for a filter unit, filter unit and filter system

[0002] The invention relates to a water inlet device for a filter unit, a filter unit and a filter system.

[0003] Water inlet devices for filter units are already known, for example, from WO 2020 / 083467 A1. The filter unit disclosed therein has an inlet through which the water to be purified flows into a water collection chamber of the filter unit. From there, the water to be purified flows upstream over a filter and is thereby purified. Purified water leaves the filter and is discharged via an outlet.

[0004] Filter devices for cleaning water contaminated with solid particles and / or dissolved pollutants, in particular surface water from street or roof drains, are known, for example, from US 8,658,044 B2 and US 7,638,066 B1.

[0005] A filter system for surface water is shown in US Pat. No. 7,638,066 B1 and comprises a filter tank in which a plurality of filter units are arranged. The filter units are each connected to a collecting line running along the bottom of the filter tank, through which purified water is discharged. The object of the invention is to provide a water inlet device, a filter unit, and a filter system for carrying out simple, cost-effective purification of water contaminated with solid particles and / or dissolved pollutants.

[0006] For this purpose, the water inlet device according to the invention has a water inlet container which delimits a water collection chamber into which at least one water inlet opening passes through a container wall of the water inlet container, wherein the water inlet container has on an upper side an outflow opening delimited by the container wall, which has a fastening interface for a filter attachment belonging to the filter unit.

[0007] The water inlet device, in particular its water inlet container, is a structural unit that can be handled separately from the filter attachment and can be individually equipped with a wide variety of filter attachments. This makes it possible, for example, to provide a filter section that always uses the same water inlet devices, but has different filter attachments. Furthermore, when used in a filter system, it is no longer necessary to remove the entire filter unit for inspection, maintenance, or to replace the filter medium; instead, the filter attachment can be removed without the water inlet device. This is made possible by the fact that the outflow opening of the water inlet device, which is particularly relatively large and has a particularly large cross-section, also provides the fastening interface for the filter unit.

[0008] In a further development of the invention, the water inlet device has at least one inlet pipe connected to the water inlet opening, the inlet pipe having an inlet opening for water to be purified at one end opposite the end facing the inlet opening. Water to be purified reaches the water collection chamber of the water inlet device via the inlet pipe. The initial treatment of the water to be purified can take place in the water collection chamber, with entrained solid particles settling at the bottom of the water collection chamber. The water collection chamber also serves as a sedimentation chamber.

[0009] Particularly preferably, the inlet pipe has an arcuately curved inlet section, which has a transition region connected to the rest of the inlet pipe and radially encloses a transition channel whose lower edge is higher than an opening level of the inlet opening. The arcuately curved inlet section can thus extend between the inlet opening and the rest of the inlet pipe in the manner of a "swan neck."With such a design it is possible in particular to retain liquids such as oil or the like which have a lower density than water and therefore collect on the water surface, since when using such a water inlet device in a filter system in which water is accumulated outside the water inlet device, the water level is always at the lower edge of the transfer channel, but the mouth level of the inlet opening is lower, so that residues on the surface such as oil or the like cannot reach the water collection chamber of the water inlet device.

[0010] Particularly preferably, the mounting interface of the water inlet device for the filter attachment is formed by the outflow opening. The filter attachment can be attached to the mounting interface without tools by simply pushing the filter attachment onto the water inlet container.

[0011] The water inlet device expediently has at least one overflow opening passing through the wall of the water inlet container, through which water can flow out, bypassing the outflow opening. This ensures reliable operation of the water inlet device in the event that normal outflow through the outflow opening is not possible, for example, if a filter medium in the filter attachment is clogged.

[0012] An overflow pipe is conveniently connected to the overflow opening, allowing overflowing water to be drained away in a targeted manner. The overflow pipe conveniently has an outlet opening at its free end, which is higher than the lower edge of the overflow channel on the inlet pipe. This ensures that overflowing water can freely escape above the accumulated water level.

[0013] In a further development of the invention, the container wall has a top wall on which the water inlet opening is located next to the outflow opening. Conveniently, in addition to the outflow opening and the water inlet opening, the overflow opening is also located on the top wall.

[0014] In a further development of the invention, the water inlet device has a drain opening extending through the wall of the water inlet tank, to which a shut-off valve is connected. The drain opening allows backwashing of the water collection chamber while bypassing the outlet opening, for example, by introducing backwash fluid, in particular rinse water, through the inlet pipe and draining through the drain opening when the shut-off valve is open.

[0015] In a particularly preferred manner, a backwash pipe is provided which projects from the container wall into the interior of the water collection chamber in the area below the outflow opening and which has a backwash opening facing the outflow opening, through which water or an air / water mixture can escape for the purpose of backwashing the filter means which can be arranged above the outflow opening.

[0016] The invention further comprises a filter unit for cleaning water contaminated with solid particles and / or dissolved pollutants, with a water inlet device according to one of claims 1 to 9, and with a filter attachment which is placed on the water inlet device and is fastened to the fastening interface of the water inlet device in a position of use covering the outflow opening.

[0017] The filter unit has two main components that can be handled separately: the water inlet assembly and the filter attachment, which can be combined to form the filter unit. This makes it possible to remove the filter attachment without removing the water inlet assembly. The water inlet assembly can therefore remain in place.

[0018] In a particularly preferred manner, the filter attachment has a particularly cylindrical attachment housing which delimits a filter medium receiving space on the circumference, in which a filter medium is received in such a way that water to be cleaned flowing in via the outflow opening of the water inlet device can flow through the filter medium in the upflow and can be cleaned in the process, wherein at least one outlet opening for cleaned water is formed on the attachment housing above the filter means and passes through a housing wall of the attachment housing.

[0019] The interaction between the outlet opening on the water inlet tank of the water inlet system and the filter attachment is ideal for upflow filtration. However, it is also possible, in principle, to use filter attachments that provide a different type of filtration than upflow filtration, depending on the water flow there.

[0020] Particularly preferably, the outlet opening is located lower than the lower edge of the inlet pipe's overflow channel. This creates a hydrostatic pressure difference between the inlet and outlet, allowing flow through the filter unit without auxiliary means such as pumps or the like.

[0021] In a particularly preferred manner, a drain pipe is connected to the drain opening, which can be connected to a clean water collection pipe receiving the cleaned water from several filter units.

[0022] Particularly preferably, the top housing has a mounting socket, particularly a cylindrical one, on its underside, which is precisely inserted into the discharge opening. It is possible for a seal, for example a ring seal, to be inserted between the outer wall of the mounting socket and the ceiling wall defining the discharge opening.

[0023] It is possible for the attachment housing to have a sieve arranged upstream of the filter medium in the direction of flow. Particularly preferably, the filter medium comprises a filter cartridge, which is particularly detachably fastened in the attachment housing and which contains a filter medium suitable for filtration. The filter medium is preferably a bed of filter particles and / or filter pads or filter bags filled with filter particles and / or a filter fabric or a filter fleece.

[0024] The invention further comprises a filter system with a filter basin, which has a filter basin inlet and a filter basin outlet arranged below the filter basin inlet, wherein a plurality of filter units according to one of claims 13 to 16 are arranged in the filter basin, each of which is connected with its outlet pipes to the associated clean water collection pipe, via which cleaned water can be transported to the filter basin outlet.

[0025] With such a filter system, a large quantity of contaminated water can be cleaned centrally, thus preventing, depending on the filter medium used, washed-out solid particles and / or dissolved pollutants from being transported further and possibly entering the soil.

[0026] In a further development of the invention, the at least one rainwater collection pipe opens into a basin-like drain section of the filter basin, wherein the filter basin drain is arranged on the wall of the drain section.

[0027] A preferred embodiment of the invention is illustrated in the drawing and will be explained in more detail below. The drawing shows: Figure 1 is a plan view of a preferred embodiment of the filter system according to the invention, with a plurality of filter units according to the invention, each having a water collection device according to the invention,

[0028] Figure 2 shows a longitudinal section through the filter system of Figure 1,

[0029] Figure 3 shows a longitudinal section through one of the filter units from Figures 1 or 2 and

[0030] Figure 4 is a perspective view of the water inlet device according to the invention as a component of the filter unit of Figure 3.

[0031] Figures 1 to 4 show a preferred embodiment of the filter system 11 according to the invention, which in the example shown is equipped with a plurality of filter units 12 according to the invention, each of which has a water inlet device 13 according to the invention.

[0032] The filter system 11 shown as an example in Figures 1 and 2 is used, in particular, to treat large quantities of surface water, which is particularly generated by precipitation in the form of rain, snow, or hail. Such surface water is generally contaminated with solid particles and / or dissolved pollutants, so that there is a need to treat this surface water, in particular to purify it, before it is available for further use. Particularly during heavy rainfall or hail, a so-called "first flush" occurs when mud, branches, leaves, waste, or other debris are washed away. The task of the filter system described in more detail below is to separate the coarse particles from the surface water, filter out the washed-away solid particles, and ideally also filter out the dissolved pollutants from the surface water.

[0033] The filter system 11 has a filter basin 14, which, in the example shown, has a rectangular layout. Of course, it is also possible to design the filter basin 14 with other layouts, for example, with a circular layout.

[0034] Conveniently, the filter basin 14 is installed deep in the ground. With this type of installation, the filter basin 14 can operate using the hydrostatic pressure difference between the inlet and outlet. In principle, however, the filter basin 14 could also be installed at ground level, although this type of installation would require the use of auxiliary equipment such as pumps or the like.

[0035] The filter basin 14 is made in particular of concrete material. The filter basin has a frame-like basin wall 15 which, as shown in particular in Figure 1, consists of two opposing longitudinal walls 16a, 16b and end walls 17a, 17b arranged in particular at right angles to them. Furthermore, the filter basin 14 has a basin floor 18 from which the basin wall 15 projects upwards. The basin wall 15 and the basin floor 18 together define an interior basin space 19 which, in turn, as shown in Figure 1, is divided into a filter section 21 and a drainage section 22 by a partition wall 20 arranged parallel to the end walls 17a, 17b. As shown in particular in Figure 2, the partition wall 20 is provided with a lower height than the end walls 17a, 17b and forms an overflow in the form of an overflow weir.

[0036] In the filter section 21 of the filter basin 14, as shown in particular in Figure 1, a plurality of filter units 12 are arranged, of which one filter unit 12 is described in more detail below by way of example.

[0037] The filter basin 14 has a filter basin inlet 23, which in the example is formed on one of the end walls 17a. Expediently, the filter basin inlet 23 is equipped with a sieve or grid (not shown) in order to prevent coarse particles that have been washed along, such as branches, leaves, and waste, from entering the filter basin. The filter basin 14 also has a filter basin outlet 24, which is formed in particular on the end wall 17b, which is opposite the end wall 17a equipped with the filter basin inlet 23. Thus, between the filter basin inlet 23 and the filter basin outlet 24 there is a filter section extending over a great length of the filter basin 14.

[0038] An important aspect here is that, as shown in particular in Figure 2, the filter basin inlet 23 is significantly higher than the filter basin outlet 24, with the filter basin outlet 24 expediently being arranged in the region of the basin floor. The filter basin inlet 23 is also arranged higher than the inlets of the filter units 12, which are described in more detail below. Thus, there is a hydrostatic pressure difference between the higher filter basin inlet 23 and the lower filter basin outlet 24, which causes the water to be cleaned flowing in via the inlet to flow out again automatically at the filter basin outlet 24 without the need for any external aids.

[0039] As shown in particular in Figure 1, at least one clean water collection pipe 25 extends within the filter basin 14, in particular along its longitudinal walls 16a, 16b; in the example shown, two parallel clean water collection pipes 25. Cleaned water flows via the clean water collection pipes 25 into the drain section 22 of the filter basin 14, for example, by the two rainwater collection pipes 25 passing through the dividing wall 20 separating the filter section 20 from the drain section 22. The clean water can then collect in the drain section 22 and drain via the filter basin drain 24.

[0040] As already mentioned, a plurality of filter units 12 are located within the filter basin 14, one of which is shown as an example in Figure 3. The filter unit 12 serves to clean water contaminated with solid particles and / or dissolved pollutants in the manner described below.

[0041] The filter unit 12 has a water inlet device 26 according to the invention, which is shown separately again in Figure 4. In addition to the water inlet device 26, the filter unit 12 has a filter attachment 27.

[0042] The water inlet device 26 shown in Figures 3 and 4 serves to collect and pretreat water to be cleaned.

[0043] The water inlet device 26 comprises a water inlet container 27, which is preferably made of plastic. The water inlet container 27 defines a water collection chamber 28 in which the inflowing water collects.

[0044] The water inlet tank 27 comprises a tank wall 29, to which a tank base 30 is connected on the underside and a ceiling wall 31 on the top.

[0045] Conveniently, fastening elements 32 are located on the tank bottom 30, for example in the form of fastening tabs, which expediently project beyond the outer circumference of the tank wall. The water inlet tank 27 can be anchored to the tank bottom 18 of the filter tank 14 using suitable mounting means.

[0046] The water inlet container 27 has at least one water inlet opening 33 passing through the container wall 29, wherein in the example shown a single water inlet opening 33 is provided.

[0047] Furthermore, the water inlet tank 27 has on its upper side, in particular on the top wall 31, an outflow opening 34 delimited by the tank wall 29, which forms a fastening interface 35 for the filter attachment 40. In the example shown, the outflow opening 34 forms the fastening interface 35 for the filter attachment 40.

[0048] In the example shown, the outflow opening 34 is a relatively large circular opening formed in the ceiling wall 31. Both the water inlet opening 33 and the outflow opening 34 are therefore located on the ceiling wall 31. Water to be cleaned flowing in through the water inlet opening 33 thus reaches the water collection chamber 28, where solid particles that are already capable of settling settle at the bottom of the water collection chamber. The water to be cleaned then flows through the outflow opening 34 into the filter attachment 40.

[0049] As shown particularly in Figure 4, an inlet pipe 36 is connected to the water inlet opening 33 of the water inlet container 27. The inlet pipe 36 has a base section 37 connected to the water inlet opening 33, which merges into an arcuately curved inlet section 38. The base section 37 extends over a large part of the height of the filter attachment 40, which will be described below.

[0050] At the free end of the outlet section 38 is an inlet opening 39 for the water to be purified. The curved inlet section 38 has a transition area 41 connected to the rest of the inlet pipe, i.e., to the base section 37, which radially encloses a transition channel 42 whose lower edge 43 is higher than the outlet level 44 of the inlet opening 39.

[0051] The arcuately curved inlet section 38 forms a type of swan neck, preventing liquids with a lower density than water, such as oil or the like, that have accumulated on the water surface from entering the filter unit 12. When the filter unit 12 is in the operating position, the water to be cleaned in the filter basin 14 reaches the lower edge 43 of the transfer channel 42 of the inlet pipe 36. However, the mouth plane 44 of the inlet opening 39 is located lower, so that the inlet does not occur from the water surface, but rather at the lower inlet opening, so that - as described above - residues on the water surface, such as oil, do not enter the filter unit 12.As further shown in particular in Figure 4, an overflow opening 45 is formed on the water inlet tank 27, in particular likewise in the region of the ceiling wall, which overflow opening 45 passes through the tank wall of the water inlet tank 27 and through which water can flow out, bypassing the outflow opening 34. An overflow pipe 46 is connected to the overflow opening 45 and is also aligned in particular parallel to the inlet pipe 36, extending along the filter attachment 40, wherein an outlet opening 47 is formed at the free end of the overflow pipe 46, through which overflow water can flow freely above the lower edge of the transfer channel 42, i.e. above the water level, into the filter basin 14.

[0052] The water inlet device 26 according to the invention also offers the possibility of backwashing in different variants.

[0053] For this purpose, the water inlet tank 27 has a drain opening 48 passing through the tank wall 29 of the water inlet tank 27, to which a shut-off device, in particular a shut-off valve 49, is connected. This makes it possible to flush the water collection chamber 28 in order to remove settled sludge. For this purpose, backwash fluid, in particular water, is fed into the water collection chamber 28 via the inlet pipe 36. If the outflow is blocked, the fluid can drain via the outflow opening 34 via the drain opening 48 when the shut-off valve 49 is open.

[0054] As shown in particular in Figure 3 and Figure 4, the water inlet device 13 has a backwash pipe 50 which projects from the container wall 15 into the interior of the water collection chamber 28 in the area below the outflow opening 34 and which has a backwash opening 51 facing the outflow opening 34, through which backwash fluid, in particular water or an air / water mixture, can escape for the purpose of backwashing the filter means 52 which can be arranged above the outflow opening.

[0055] As already mentioned, the filter unit 12 comprises, in addition to the water inlet device 13 described above, a filter attachment 40 which is placed on the water inlet device 26, in particular its water inlet container 27, and is fastened to the fastening interface 35 of the water inlet device 13 in a position of use covering the outflow opening 34.

[0056] The filter attachment 40 is also conveniently made of plastic material.

[0057] The filter attachment 40 has a particularly cylindrical attachment housing 53 which delimits a filter medium receiving space 54 on the circumference, in which a filter medium 52 is received in such a way that water to be cleaned flowing in via the outflow opening 34 can flow through the filter medium 52 in the upflow and is cleaned in the process, wherein at least one outlet opening 56 for cleaned water is formed above the filter medium 52 on the attachment housing 53 and passes through a housing wall 55 of the attachment housing 53.

[0058] The attachment housing 53 of the filter attachment 40 has an attachment housing base 57 which has a through-flow opening 58 substantially corresponding to the cross-section of the outflow opening. A fastening nozzle 59, in particular a cylindrical one, extends outwardly from the attachment housing base 57 and, in the use position of the filter attachment 40, is inserted with a precise fit into the outflow opening 34. A seal, in particular an annular seal, for example in the manner of a sealing ring, is inserted between the outer wall or lateral surface of the fastening nozzle 59 and the section of the top wall 31 surrounding the outflow opening 34.

[0059] Advantageously, the cross-section, in particular the diameter of the fastening nozzle 59, is smaller than the cross-section or diameter of the top housing base 57. This forms an annular shoulder radially between the outer wall of the fastening nozzle and the housing wall 55 of the top housing, which shoulder rests on the top wall 31 of the water inlet tank 27 in the state of use.

[0060] The attachment housing 53 has a screen 61 arranged upstream of the filter media in the flow direction. The screen conveniently rests on the annular shoulder 60, thus being directly associated with the flow opening 58.

[0061] As already mentioned, water to be purified entering the filter attachment 40 is conveyed in an upflow through the filter medium 52. The filter medium 52 or filter substrate can have a filter cartridge (not shown), which is particularly detachably attached to the attachment housing 53 and in which a filter medium 62 suitable for filtration is accommodated.

[0062] In the example shown, the filter medium 62 is a bed of particles so that, depending on the type of particle used, dissolved pollutants can also be filtered out of the water in addition to the solid particles.

[0063] As already mentioned, the drain opening 56 is formed in the housing wall 55 of the attachment housing 53 above the filter media. It is important that the drain opening 56 is located lower than the lower edge 43 of the overflow channel 42 of the inlet pipe 36, which defines the maximum water level of the filter basin 14. This also creates a hydrostatic pressure difference between the higher inlet and the lower outlet in the area of ​​the filter unit 12, enabling upflow filtration in the manner described above without additional aids.

[0064] As shown in particular in Figure 3, a drain pipe 63 is connected to the drain opening 56, which is connected to the previously described clean water collection pipe 25.

[0065] As shown particularly in Figures 1 and 2 and mentioned above, a plurality of filter units 12 are arranged in the filter basin 14, which are expediently constructed identically to one another, as described above. The filter units 12 are each connected by their outlet pipes 63 to one of the clean water collection pipes 25.

[0066] The purification of surface water by the filter system 11 according to the invention proceeds as follows:

[0067] Surface water contaminated with solid particles and dissolved pollutants enters the filter tank 14 via the filter tank inlet 23. In the filter tank 14, the contaminated surface water is accumulated up to the lower edges of the transfer channels 42 of the inlet pipes of the filter units 12. As a rule, therefore, there is always a water level in the filter tank 14 that is accumulated up to the lower edges of the inlet pipes 36 of the filter units 12. The contaminated surface water then passes through the inlet openings 39 of the respective inlet pipes and through the water inlet openings into the water inlet container 27 of the respective filter units 12. As already mentioned above, the curved inlet section 38 of the inlet pipe 36 prevents liquids or objects that are lighter than water from entering the filter unit 12, since they collect on the water surface, the mouth level of the inlet opening, i.e. the inlet, is lower.In the water collection chamber 28, a pretreatment of the contaminated surface water already takes place, in the sense that washed-up solid particles settle at the bottom of the water collection chamber 28. Water then flows through the outflow opening 34 of the water collection container 27 into the filter attachment 40 arranged above it and flows through the filter medium 62 located in the filter attachment 40 in an upflow.

[0068] Purified water then emerges in the flow direction downstream of the filter medium 62, i.e., at the top of the filter medium, and is transported via the drain opening 56 and the drain pipe 63 to the clean water collection pipe 25. From the clean water collection pipe 25, the purified surface water then flows into the drain section 22 of the filter basin 14 and is then discharged via the filter basin drain 24.

[0069] The two previously mentioned backwash processes proceed as follows:

[0070] To backwash the water collection chamber 28, the outflow through the outflow opening 34 is blocked, and rinse water is introduced into the water collection chamber 28 via the inlet pipe 36. There, the rinse water carries the settled sludge and is discharged from the water collection chamber via the drain opening with the shut-off valve open.

[0071] To backwash the filter medium 52, a backwash fluid, in particular an air / water mixture, is passed through the backwash pipe into the area below the outflow opening 34 and then exits at the backwash opening 51, the available fluid pressure pressing the air / water mixture in the upflow through the filter medium 52, solid particles separated in the filter medium 62 of the filter medium 52 being washed to the surface of the filter medium 52 and then being discharged via the outlet opening 56, the outlet pipe 63 in this case being separated from the clean water collection pipe 25, so that the residues reach the filter basin 14.

Claims

Claims 1. Water inlet device for a filter unit (12), with a water inlet container (27) which has a water collection chamber (28) into which at least one container wall (29) of the water inlet container (27) opens into a water inlet opening (33), wherein the water inlet container (27) has on an upper side an outflow opening (34) delimited by the container wall (29), which has a fastening interface (35) for a filter attachment (40) belonging to the filter unit (12).

2. Water inlet device according to claim 1, characterized by at least one inlet pipe (36) which is connected to the water inlet opening (33), wherein the inlet pipe (36) has an inlet opening (39) for water to be purified at one end which is opposite to the end facing the water inlet opening (33).

3. Water inlet device according to claim 2, characterized in that the inlet pipe (36) has an arcuately curved inlet section (38) which has a transfer area (41) connected to the rest of the inlet pipe (36) and which radially encloses a transfer channel (42) whose lower edge (43) is higher than an opening plane (44) of the inlet opening (39).

4. Water inlet device according to one of the preceding claims, characterized in that the fastening interface (35) is formed by the outflow opening (34).

5. Water inlet device according to one of the preceding claims, characterized by at least one overflow opening (45) passing through the container wall of the water inlet container (27), through which water can flow out, bypassing the outflow opening (34).

6. Water inlet device according to claim 5, characterized in that an overflow pipe (46) is connected to the overflow opening (45).

7. Water inlet device according to one of the preceding claims, characterized in that the container wall (29) has a top wall (31) on which the water inlet opening (33) is located next to the outflow opening (34), wherein preferably in addition to the outflow opening (34) and the water inlet opening (33) the overflow opening (45) is also located on the top wall (31).

8. Water inlet device according to one of the preceding claims, characterized by an emptying opening (48) passing through the container wall (29) of the water inlet container (27), to which a shut-off means, in particular a shut-off valve (49) is connected.

9. Water inlet device according to one of the preceding claims, characterized by a backwash pipe (50) projecting from the container wall (29) into the interior of the water collecting chamber (28) in the area below the outflow opening (34), which has a backwash opening facing the outflow opening (34) (51) through which water or an air / water mixture can escape for the purpose of backwashing the filter means (52) which can be arranged above the outflow opening (34).

10. Filter unit for cleaning water contaminated with solid particles and / or dissolved pollutants, with a water inlet device (13) according to one of claims 1 to 9, and with a filter attachment (40) which is placed on the water inlet device (13) and is fastened to the fastening interface (35) of the water inlet device (13) in a position of use covering the outflow opening (34).

11. Filter unit according to claim 10, characterized in that the filter attachment (40) has a particularly cylindrical attachment housing (53) which defines a filter medium receiving space (54) on the circumference, in which a filter medium (52) is received in such a way that water to be cleaned flowing in via the outflow opening (34) of the water inlet device (13) can flow through the filter medium (52) in an upflow and can be cleaned in the process, wherein above the filter medium (52) on the attachment housing (53) at least one outlet opening (56) for cleaned water is formed, passing through a housing wall (55) of the attachment housing (53).

12. Filter unit according to claim 10 or 11, characterized in that the drain opening (56) is located lower than the lower edge (43) of the transfer channel (52) of the inlet pipe (36).

13. Filter unit according to one of claims 10 to 12, characterized in that a drain pipe is connected to the drain opening (56). (63) which can be connected to a clean water collection pipe (25) receiving the cleaned water from several filter units (12).

14. Filter unit according to one of claims 10 to 13, characterized in that the attachment housing (53) has on its underside a fastening piece (59), in particular of a cylindrical design, which is inserted with a precise fit into the outflow opening (34).

15. Filter unit according to one of claims 10 to 14, characterized in that the attachment housing (53) has a sieve (61) arranged upstream of the filter means (52) in the flow direction.

16. Filter unit according to one of claims 10 to 15, characterized in that the filter means (52) has a filter cartridge, in particular detachably fastened in the attachment housing (53), in which a filter medium (62) suitable for filtration is accommodated, wherein preferably the filter medium (62) is a bed of filter particles and / or filter pads or filter bags filled with filter particles and / or a filter fabric or a filter fleece.

17. Filter system with a filter tank (14) which has a filter tank inlet (23) and a filter tank outlet (54) arranged below the filter tank inlet (23), wherein a plurality of filter units (12) according to one of claims 13 to 16 are arranged in the filter tank (14), each of which is connected with its outlet pipes (63) to the associated clean water collection pipe (25), via which cleaned water can be transported to the filter tank outlet (24).

18. Filter unit according to claim 17, characterized in that the at least one rainwater collection pipe (25) opens into a basin-like drain section (22) of the filter basin (14), wherein the filter basin drain (24) is arranged on the wall of the drain section (22).

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