JP2008208521A - Rainwater storage facility - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rainwater storage facility sufficiently coping with flood prevention as an infiltrating type water storage facility even in torrential rain and having ability to serve as a storage type water storage facility usable for water sprinkling or the like. <P>SOLUTION: The rainwater storage facility has a water storage part 2 provided by digging down the ground 1; a permeable sheet 3 covering a bottom face and a side face of the water storage part 2; an impervious sheet 4 covering the bottom face and a side face lower part continuous with the bottom face out of the bottom face and side face of the water storage part 2 covered with the permeable sheet 3; a space holding skeleton constituted by building up a plurality of skeleton blocks 5 and disposed in the water storage part 2 covered with the permeable sheet 3 and impervious sheet 4; and a covering layer 7 covering the upper face of the water storage part 2. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a rainwater storage facility formed in a basement of a parking lot or a bicycle parking lot such as a building, an apartment house, or a detached house.

Conventionally, for example, in order to prevent rainwater from flowing out into rivers suddenly during heavy rains, or to use rainwater for fire prevention, for sprinkling water in flower beds or gardens, and for car washing, etc. Various attempts have been made to store rainwater in vacant lots around buildings and housing complexes, or in the underground of parking lots and bicycle parking lots.
Especially in recent years, this kind of rainwater storage facilities are often provided when building a new housing complex in preparation for water shortages in summer.

  Recently, the use of rainwater has been considered not only in large buildings and housing estates, but also in detached houses. Specifically, it is considered to be used for watering a flower bed or a garden, or for car washing or washing.

As mentioned above, this type of water storage facility includes an infiltration type water storage facility designed to prevent urban flooding by preventing rainwater from flowing into rivers suddenly during heavy rains, and for fire prevention. There are storage-type water storage facilities that store rainwater for watering, car washing, and washing.
The former covers the inner surface of the water reservoir formed by digging the ground, generally with a water-permeable sheet, and infiltrates the stored rainwater into the ground, preventing rainwater from flowing into the river suddenly during heavy rains. is doing.
On the other hand, in the latter storage type, the inner surface of the water storage part is covered with a water shielding sheet so that the stored rainwater does not leak into the ground and can be used for a long time.

By the way, in recent years, due to global warming, heavy rains continue or droughts continue, and the change in weather has become extremely large. Therefore, preventing urban floods during heavy rains and preventing water shortages during droughts Measures for both are urgently needed.
In response to such problems, rainwater storage that combines so-called permeation type and storage type that can be used for fire prevention and sprinkling, etc., while allowing the stored rainwater to penetrate into the ground and partially using it for fire prevention Facilities are being sought.

Generally speaking, it is conceivable to separately provide both an infiltration type and a storage type rainwater storage facility, but it is difficult to install the apartment itself in condominiums and detached houses where installation locations are limited. In addition, providing two water storage facilities is a problem because it is expensive.
Therefore, as described in Patent Document 1, a rainwater storage facility that has both an infiltration type and a storage type has been proposed.

Japanese Patent No. 3103300 (Japanese Patent Laid-Open No. 9-111814)

The water storage facility disclosed in Patent Document 1 covers a side surface of a water storage portion formed by digging the ground with a water permeable sheet, and then a lower portion of the side surface covered with the water permeable sheet, In this way, from the bottom of the water storage part to about 2/3 of the entire depth is further covered with a water-permeable mat, and finally the bottom surface of the water storage part and the water-permeable mat are covered with a water-impervious sheet. The water storage part filled with porous gravel-like water storage material.
In the water storage facility described in Patent Document 1 thus configured, a depth of about 2/3 from the bottom of the water storage section covered with the water shielding sheet is not covered with the storage type water storage facility or the water shielding sheet. The upper part of the water reservoir is an osmotic water storage facility.
In the case of such a water storage facility, with respect to the water storage, the amount of stored water can be reliably maintained almost as designed, and the purpose of the storage type facility can be almost achieved. However, in the case of heavy rain, the penetration of rainwater flowing into this water storage facility into the ground is insufficient, and the function as a so-called water storage facility for preventing urban flooding is insufficient.

The reason is that the penetration of rainwater that has flowed into the water storage part into the ground is the upper part of the side part of the water storage part that is not covered with the water-impervious sheet, specifically, the upper part of the side surface corresponding to 1/3 of the depth. Infiltration from the lower part of the side surface corresponding to the remaining 2/3 depth through the water-permeable mat sandwiched between the water-permeable sheet and the water-impervious sheet, that is, from the four side surfaces of the water storage part This is because almost no penetration from the bottom of the reservoir is expected.
Therefore, if the amount of rainwater inflow into the reservoir is increased due to heavy rain, the infiltration into the ground will not be in time, and as soon as it flows into the reservoir, it immediately flows out from the outlet of the reservoir to the drainage channel connected to the river. There is a problem that the original purpose of preventing urban flooding cannot be achieved.

  In view of the above-mentioned problems, the object of the present invention is to provide rainwater that can sufficiently cope with flood prevention as a seepage-type water storage facility even during heavy rains, and also has a capacity as a storage-type water storage facility that can be used for watering etc. The purpose is to provide water storage facilities.

  In order to achieve the above object, a rainwater storage facility according to claim 1 of the present invention includes a water storage section provided by digging the ground, a water permeable member that covers a bottom surface and a side surface of the water storage section, and the water permeable member. A water-impervious sheet that covers the bottom surface and the lower part of the side surface that continues to the bottom surface of the covered water reservoir, and a plurality of water-receptors disposed in the water reservoir that is covered with the water-permeable member and the water-impervious sheet. It has the space holding | maintenance frame | skeleton comprised by assembling the skeleton block, and the coating layer which covers the upper surface of the said water storage part.

  The rainwater storage facility according to claim 2 is the rainwater storage facility according to claim 1, wherein the water permeable member is one of a water permeable sheet, a water permeable filling material, a water permeable member, or a combination thereof. It is characterized by being.

  Furthermore, the rainwater storage facility according to claim 3 includes a water storage section provided by digging down the ground, a water permeable sheet covering a bottom surface and a side surface of the water storage section, and the water permeable sheet covered with the water permeable sheet. A water-impervious sheet that covers the bottom surface and the lower part of the side surface connected to the bottom surface of the bottom surface and the side surface of the water reservoir, and a plurality of skeleton blocks disposed in the water reservoir covered with the water-permeable sheet and the water-impervious sheet In a rainwater storage facility having a space holding skeleton constructed by assembling and a covering layer covering the upper surface of the water storage section, between the water-permeable sheet and the water shielding sheet on the side surface of the water storage section It is characterized by being filled with a water-permeable filling material.

In addition, the rainwater storage facility according to claim 4 is covered with a water storage section provided by digging the ground, a water permeable sheet that covers a bottom surface and a side surface of the water storage section, and the water permeable sheet. A water shielding sheet that covers the bottom surface and the lower part of the side surface connected to the bottom surface of the water storage section, and a plurality of skeletons disposed in the water storage section covered with the water permeable sheet and the water shielding sheet. In a rainwater storage facility having a space holding skeleton constructed by assembling blocks and a coating layer covering the upper surface of the water storage section, a water-conducting member is provided between the water-permeable sheet and the water-impervious sheet. It is characterized by being.
The rainwater storage facility according to claim 5 is the rainwater storage facility according to claim 2 or claim 4, wherein the water-conducting member is a hollow plate member, a porous plate member or a porous pipe having a large number of water passage holes. It is characterized by.

According to the rainwater storage facility of the present invention thus configured, for example, in the case of heavy rain, the rainwater that has flowed into the water storage portion oozes out from the upper side surface of the water storage portion covered only with the water permeable member, Specifically, it is possible to quickly wrap around the lower portion and the bottom surface of the water storage unit covered with the water-impervious sheet through the water-permeable sheet, the water-conducting member, or the water-permeable filling material.
As a result, the rainwater that has flowed into the water reservoir can quickly penetrate into the ground not only from the side surface of the water reservoir but also from the bottom surface, that is, from the entire inner surface of the water reservoir. Therefore, it has sufficient capability not only as a storage type storage facility for watering but also as an infiltration type storage facility for preventing flooding.

  As described above, according to the rainwater storage facility of the present invention, it can sufficiently cope with flood prevention as an infiltration type storage facility even during heavy rains, etc., and also has the capability as a storage type storage facility that can be used for watering etc. Rainwater storage facilities can be provided.

Hereinafter, embodiments of the rainwater storage facility of the present invention will be described in detail with reference to FIGS. FIG. 1 is a schematic sectional view showing an embodiment of the rainwater storage facility of the present invention.
As shown in FIG. 1, the ground surface 1 is dug down to form a water reservoir 2 having a planar shape of, for example, a substantially rectangular shape or a substantially square shape. Thereafter, the entire inner surface of the water storage unit 2, that is, the entire bottom surface and side surfaces are covered with a water permeable member, here, the water permeable sheet 3. As the water permeable sheet 3, for example, one or a plurality of non-woven fabrics having a thickness of about 5 mm are used. The non-woven fabric is fine and allows water to pass through, but the inner surface of the water reservoir 2, that is, the earth and sand so that fine earth and sand does not enter the water reservoir 2 from the inside of the water reservoir 2 and accumulate in the water reservoir 2. It also acts as an intrusion prevention member.
The seam is bonded by welding or the like so that earth and sand do not enter from the seam of the water-permeable sheet 3.

Next, portions corresponding to the bottom surface and the lower portion of the side surface of the water storage portion 2 inside the water permeable sheet 3 are covered with a rubber water shielding sheet 4 such as EPDM (ethylene propylene rubber). At this time, the seam of the water shielding sheet 4 is, for example, thermally welded so as not to leak. In order to protect the water shielding sheet 4, a thicker nonwoven fabric than the water permeable sheet 3 may be further stacked on the water shielding sheet 4.
Here, the lower portion of the side surface refers to a side surface portion that is connected to the bottom surface and corresponds to about 1/4 to 3/4 of the depth of the water storage section 2 from the bottom surface. In the range of 1/4 to 3/4 of the depth of the water storage unit 2, the specific amount is the size of the water storage unit 2 and its purpose, that is, the main purpose is to prevent flooding, or water storage for watering etc. Is selected as appropriate depending on whether the main purpose is.

When the side surface and the bottom surface of the water storage section 2 are thus covered with the water permeable sheet 3 and the water shielding sheet 4, a resin, for example, polypropylene, is formed on the water shielding sheet 4 on the bottom surface of the water storage section 2. A plurality of skeleton blocks 5 (hereinafter referred to as resin skeleton blocks 5) are connected vertically and horizontally to form a space holding skeleton. Incidentally, in FIG. 1, only a part of the resin skeleton block 5 is shown to simplify the drawing, and most of the skeleton block 5 is omitted. Incorporated.
The resin skeleton block 5 shown in FIG. 1 is made of a resin in which a square frame is integrally formed on the top and bottom of a cylindrical body. Each of which has a fitting hole, and the connecting projections are fitted into the mating fitting holes and sequentially connected to form a space holding skeleton.

  The resin skeleton block 5 has been proposed in various shapes, and there are, for example, a box shape, a cylindrical shape, a tray shape and the like in addition to the resin skeleton block 5 shown in FIG. Therefore, the present invention is not limited to that shown in FIG. Incidentally, it is preferable that the water storage porosity of the space holding skeleton formed in the water storage section 2 by the resin skeleton block 5 is 90% or more.

After forming the space holding skeleton by the resin skeleton block 5 in the entire water storage part 2, for example, a top plate is placed thereon if necessary, and then a water-permeable sheet 6 made of nonwoven fabric or the like is placed thereon, Further, the covering layer 7 is formed by, for example, backfilling the dug up soil.
In FIG. 1, reference numeral 9 denotes an inflow port of rainwater to the rainwater storage facility, and a sedimentation tank 10 for precipitating large earth and sand such as stones and gravel is provided immediately before that. Reference numeral 11 denotes a manhole for monitoring the state in the water storage unit 2, for example, sedimentation state of earth and sand. Reference numeral 12 denotes an outlet of the water storage unit 2, and reference numeral 13 is connected to the outlet 12. Reference numeral 14 denotes a rainwater pumping pit, which is a pump for pumping rainwater installed at the bottom of the rainwater pumping mine 13.

The water-permeable sheet 3 and the water-impervious sheet 4 described above are prepared in advance in the factory according to the size of the water storage part 2 and the seam is thermally welded in the factory, and this is dug in the ground 1. If it is installed in the water storage section 2, it is possible to use one that can be joined more reliably.
The reason is that in the case of the water permeable sheet 3, fine particles of soil from the surface of the water storage unit 2 (the surface of the earth and sand) will enter the inside of the water storage unit 2 if the joints are securely joined. This is because it is possible to prevent the intrusion more reliably, and in the case of the water shielding sheet 4, the water stored in the water storage section 2 can be more difficult to leak into the ground.

By the way, not only the case where the water-permeable sheet 3 or the water-impervious sheet 4 previously formed into a bag shape is brought into the water storage part 2 but also the work of welding the water-permeable sheet 3 and the water-impervious sheet 4 in the water storage part 2. For example, in order to facilitate the work, a hole having a larger capacity than that of the planned water storage unit 2 is usually dug in the ground 1.
As a result, in the case of the rainwater storage facility shown in FIG. 1, a gap is often formed between the inner surface of the dug water storage portion 2, that is, the earth and sand surface and the water permeable member, for example, the water permeable sheet 3. In the case where a gap is formed in this way, it is only necessary to backfill the remaining soil or the like that has come out when the water storage unit 2 is dug into the gap later. Incidentally, in this specification, including the other embodiments of the present invention described below, when the remaining soil or the like is backfilled, the water permeable member such as the water permeable sheet 3 and the backfill The interface with the remaining soil and the like is defined as the surface of the water storage unit 2 (sediment surface).

In the rainwater storage facility shown in FIG. 1 constructed as described above, the amount of rainwater flowing into the water storage unit 2 increases rapidly during heavy rain, and the lower part of the water storage unit 2 is covered with the water shielding sheet 4. When the water does not accumulate in the water, it overflows from the upper end of the water-impervious sheet 4 and penetrates into the ground from the side surface covered only with the water-permeable sheet 3. At the same time, the water-permeable sheet 3 covers the outside of the water-impervious sheet 4 and extends to the side surface and bottom surface of the lower part of the water storage section 2, so that overflowing rainwater travels through this water-permeable sheet 3 and stores water. It reaches the lower side and bottom of the side surface of part 2, and can penetrate into the ground from there and escape.
That is, in the rainwater storage facility shown in FIG. 1, the permeable sheet 3 directly covers the entire inner surface of the water storage part 2, so that rainwater can penetrate into the ground from the entire inner surface of the water storage part 2. Yes. As a result, even during heavy rain, the rainwater that has flowed into the water storage section 2 can be quickly permeated into the ground to escape, and a sudden rainwater flow into the river from this rainwater storage facility can be mitigated.

FIG. 2 shows another embodiment of the rainwater storage facility of the present invention. FIG. 2 is a schematic cross-sectional view of the rainwater storage facility as in FIG. The same components as those in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted.
The feature of the rainwater storage facility shown in FIG. 2 is that there is water permeability between the water permeable sheet 3 and the water shielding sheet 4 on the side surface of the water storage section 2 of the rainwater storage facility shown in FIG. The water-permeable filling material 15 made of, for example, crushed stone, a spherical or pipe-shaped resin molded body, or a metal molded body is filled. Reference numeral 16 denotes a water permeable sheet made of a nonwoven fabric or the like provided so that the water permeable filling material 15 does not fall into the water storage portion 2. The lower end of the water-permeable sheet 16 is welded to the upper end of the water-impervious sheet 4 to cover the upper part of the four side surfaces.

According to the rainwater storage facility shown in FIG. 2, rainwater overflowing beyond the water storage portion 2 covered with the water shielding sheet 4 permeates from the water permeable sheet 16 to the water permeable filling material 15, and this water permeable water. From the entire side surface of the water storage unit 2 through the permeable intermediate filling material 15, and simultaneously to the permeable sheet 3 covering the entire bottom surface of the water storage unit 2 through this water permeable intermediate packing material 15, It penetrates quickly into the inside.
In the case of the rainwater storage facility shown in FIG. 2, the rainwater overflowing from the upper end of the water shielding sheet 4 wraps around the bottom surface of the water storage unit 2 only through the permeable sheet 3, compared with the rainwater storage facility shown in FIG. In addition to the water permeable sheet 3, the water penetrates into the lower portion of the side surface through the water permeable filling material 15 having a large porosity, so that the amount of moisture transferred from the side surface portion to the bottom surface portion increases, and the side surface and bottom surface are further increased. Penetration into the ground is promoted.
As a result, even in the case of torrential rain, rainwater that has flowed into the water storage section 2 can be permeated into the ground more quickly and escaped, and sudden rainwater can be prevented from flowing into the river from this rainwater storage facility. .
By the way, the water-permeable sheet 3 on the outer side of the water-permeable intermediate filling material 15 and the water-permeable sheet 16 on the inner side can be omitted. However, when the water-permeable sheet is installed, fine earth and sand of particles enter the water storage part 3 from the surface (sediment surface) of the water storage part 3 through the water-permeable filling material 15. It is possible to prevent the water-permeable filling material 15 from collapsing into the water storage unit 3 and to prevent the water-permeable filling material 15 from falling.

FIG. 3 is a schematic sectional view showing still another embodiment of the present invention.
The rainwater storage facility shown in FIG. 3 is characterized by the entire area between the water permeable sheet 3 and the water shielding sheet 4 in the rainwater storage facility shown in FIG. The water-conducting member 18 is disposed on the entire side surface and bottom surface.
As this water-conducting member 18, for example, a hollow plate as shown in FIG. 4, i.e., a thin section rectangular pipe provided with a large number of water holes 19 communicating from the outside to the inside cavity, As shown in FIG. 5, a porous resin plate having a large number of water passage holes 19 communicating with each other in each direction, or a porous pipe as shown in FIG. 6, that is, a large number of resin pipes communicating with the inner cavity of the pipe. Other than these, those having a plurality of water passage holes 19 having a U-shaped cross section and communicating with the inside and the outside of the U shape can be used.
Incidentally, these water guide members 18 may be made of any material as long as it has mechanical strength capable of withstanding the weight of water stored in the water storage section 2 and ensuring a water channel. However, it is preferable that the resin is made of polyethylene, polypropylene, or the like in consideration of assembling property and transportability.

  In addition, when the plate-shaped thing as shown in FIG.4 and FIG.5 is used as the water-conducting member 18, these water-conducting members 18 are the surface of the water storage part 2, ie, the earth and sand surface side, and the water storage part 2 inside. Since it also acts as an earth and sand invasion prevention material, the water permeable sheet 3 in the portion overlapping the water guide member 18 may be omitted. Of course, the water-permeable sheet 3 is preferable because it can prevent the intrusion of earth and sand more reliably.

FIG. 7 is a partially enlarged view of the lower left portion of the rainwater storage facility shown in FIG. Here, what is shown in FIG. 4 is installed in the bottom face of the water storage part 2 as the water conveyance member 18, and what is shown in FIG. 5 is arrange | positioned in the side surface side.
In the rainwater storage facility shown in FIG. 3 and FIG. 7, when rainwater collected in the lower part of the water storage part 2 covered with the water shielding sheet 4 exceeds the upper end of the water shielding sheet 4, the water-conducting member 18 having a large porosity. Thus, the water is quickly transported to the entire lower portion of the side surface of the water reservoir 2 and to the bottom surface. As a result, the water permeation holes 19 formed in these water-conducting members 18 quickly infiltrate into the ground on the earth and sand surface side (bedrock side) of the water reservoir 2. In particular, when a hollow interior is used as shown in FIGS. 4 and 6, the rainwater overflowing from the reservoir 2 is moved to the bottom surface of the reservoir 2 in a very short time. It becomes possible to increase the amount of penetration into the city, and it is possible to further enhance the urban flood prevention effect.

1 shows an example in which the water-permeable sheet 3 is used as the water-permeable member, but the water-permeable filling material 15 and the water-conducting member 18 are each independently used instead of the water-permeable sheet 3. It may be used. Alternatively, the water-permeable sheet 3, the water-permeable intermediate filling material 15, and the water-conducting member 18 may be used in appropriate combination.
For example, the water-conducting member 18 may be provided on the side surface of the water reservoir 2 and the water-permeable filling material 15 may be installed on the bottom surface. Each of them is used alone or in combination with the water-impervious sheet 4, or as a water-permeable member, a water-permeable sheet and a water-permeable filling material, or a water-permeable filling material and a water-conducting member, or a combination of these three. Whether to combine with the water-impervious sheet 4 may be determined in consideration of various conditions such as the size of the water reservoir 2 and the drainage of the place where the water reservoir 2 is installed.

As described above, in the rainwater storage facility of the present invention, the rainwater overflowing from the lower part of the water storage part 2 covered with the water shielding sheet 4 in any case is the permeable sheet 3 or the water permeable filling. Via the material 15 or the water-conducting member 18, not only the side surface of the water storage unit 2 but also the bottom surface can be wound. Therefore, the area where rainwater can permeate can be greatly expanded, and the overflowing rainwater can permeate into the ground in a shorter time and escape.
As a result, this rainwater storage facility can be further enhanced not only as a storage-type storage facility for the purpose of watering but also as an infiltration-type storage facility for preventing urban flooding.
By the way, in recent large-scale stores in the suburbs, rainwater storage facilities with a depth of about 2 m or less and a bottom area exceeding 10,000 square meters have been constructed. In the case where the area of the bottom surface is larger than that of the side surface, such as the rainwater storage facility of the present invention, which can infiltrate rainwater into the ground also from the bottom surface, has a great flood prevention effect.

  As described above, according to the present invention, a rainwater storage facility capable of adequately preventing flooding as a seepage-type water storage facility in the event of heavy rain, etc., and also having a capacity as a storage-type water storage facility that can be used for watering etc. Can be provided.

It is a schematic sectional drawing which shows one Example of the rainwater storage facility of this invention. It is a schematic sectional drawing which shows another Example of the rainwater storage facility of this invention. It is a schematic sectional drawing which shows another Example of the rainwater storage facility of this invention. It is a perspective view which shows an example of the water-conducting member shown in FIG. It is a perspective view which shows another example of the water-conducting member shown in FIG. It is a perspective view which shows another example of the water-conducting member shown in FIG. It is a partially expanded view of the left end lower part of the rainwater storage facility shown in FIG.

Explanation of symbols

2 Water storage part 3 Water-permeable sheet 4 Water-impervious sheet 5 Resin skeleton block 6 Water-permeable sheet 7 Coating layer 9 Inlet 12 Outlet 13 Rainwater pumping pit 15 Water-permeable filling material 18 Water-conducting member 19 Water flow Hole

Claims (5)

  A water storage section provided by digging down the ground, a water permeable member covering the bottom surface and the side surface of the water storage section, and the bottom surface and the side surface of the water storage section covered with the water permeable member. A water-impervious sheet that covers the lower side of the side surface, a space-retaining skeleton that is configured by assembling a plurality of skeleton blocks disposed in the water reservoir covered with the water-permeable member and the water-impervious sheet, and an upper surface of the water reservoir A rainwater storage facility characterized by having a covering layer for covering.   The rainwater storage facility according to claim 1, wherein the water permeable member is one of a water permeable sheet, a water permeable filling material, a water permeable member, or a combination thereof.   A water storage section provided by digging down the ground; a water-permeable sheet that covers a bottom surface and a side surface of the water storage section; and the bottom surface and the bottom surface of the water storage section covered with the water-permeable sheet. A water-impervious sheet that covers the bottom of the side surface connected to the bottom surface, and a space-retaining skeleton that is configured by assembling a plurality of skeleton blocks disposed in the water storage section covered with the water-permeable sheet and the water-impervious sheet. In the rainwater storage facility having a covering layer covering the upper surface of the water storage unit, a water-permeable filling material is filled between the water-permeable sheet and the water-impervious sheet on the side surface of the water storage unit. A rainwater storage facility characterized by   A water storage section provided by digging down the ground; a water-permeable sheet that covers a bottom surface and a side surface of the water storage section; and the bottom surface and the bottom surface of the water storage section covered with the water-permeable sheet. A water-impervious sheet that covers the bottom of the side surface connected to the bottom surface, and a space-retaining skeleton that is configured by assembling a plurality of skeleton blocks disposed in the water storage section covered with the water-permeable sheet and the water-impervious sheet. A rainwater storage facility having a covering layer covering an upper surface of the water storage section, wherein a water-conducting member is provided between the water-permeable sheet and the water-impervious sheet.   The rainwater storage facility according to claim 2 or 4, wherein the water-conducting member is a hollow plate member, a porous plate member or a porous pipe having a large number of water passage holes.

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