BE1026473B1 - Rainwater tank - Google Patents

Abstract

The tank is provided with a porous concrete inner wall (8) to define a storage space (3.30) and a buffer space (9.90.91). The inner wall is made of a water-draining concrete with a maximum water permeability of 0.05 liters / m2 / s to 5 liters / m2 / s, preferably of 0.1 liters / m2 / s to 3 liters / m2 / s, wherein that water permeability has been measured at an almost water-rich storage space (3).

Description

Rainwater tank

The invention relates to a rainwater tank, in particular a rainwater buffer.

More and more houses and other buildings are equipped with water tanks to store rainwater. In the event of insufficient use of water, the water tanks will remain almost full of water, and in case of heavy rain they will not purchase a solution against excessive water drainage.

To solve storm water problems, a system is used that plastic modules package together in a porous textile material. Building such a system requires underground works to achieve sufficient soil stability. A top layer is also useful for being able to ride it.

Water tanks that can also be used as drainage systems are described, for example, in WO95 / 16833. In the draining system according to this document, perforated walls and porous textile material are used to define a storage volume, wherein water flows through the walls and the porous textile material to allow water to infiltrate into the soil itself.

Such a system requires earthworks to be sure that there is a porous base layer around the walls with the porous textile material. In addition, in case of wet soils, are so

BE2018 / 0079 systems totally inefficient. Indeed, groundwater flows into the tank through the porous side walls, thus limiting the space for collecting rainwater.

The use of porous concrete layers is also known for driveways, roads and parking. The porous concrete has a very high permeability and is intended to carry water to an underlying layer of soil. As soon as that primer is wet, the efficiency of the porous concrete will decrease.

All these known systems are not efficient solutions for controlling the drainage of rain water to streams or rivers during a rainy period and after a rainy period, for example in case the soil is too wet.

The invention is a water tank for storing rainwater / water. With the water tank according to the invention, the installation of a porous primer around the tank is no longer necessary. The drainage of rainwater does not depend on the soil layer in which the tank is placed. By effectively controlling the rainwater discharge by means of one or more water tanks according to the invention, it is possible to control the water flow that flows to the rivers, canals, streams, flood areas, etc. Water tanks according to the invention can also be used as a means to control water levels in canals, canals, rivers, etc.

For example, water tanks according to the invention can be used along (and / or as part of) cribs, dams, towpaths and inspection paths of canals, canals, streams, rivers, etc. to at least partially control water levels.

In case it is necessary, the porous concrete wall can be easily cleaned.

The water tank according to the invention is a water tank for collecting and storing (at least temporarily) rainwater / water,

BE2018 / 0079 and for controlled water drainage. The water tank comprises at least:

- one or more outer walls (1) which are / are made of non-porous concrete and which define an inner volume (2), a part of which serves as storage space (3) for rainwater / water;

- an inlet opening (4) through which rainwater / water can flow into the storage space (3);

- an outlet opening (5) for draining rainwater / water from the water tank (T);

- a lid (6) with a manhole (7); and

- a control system (5,8) to control the drainage rate of rainwater / water from the water tank (T).

According to the invention, the water tank is essentially characterized in that the control system (5, 8) consists of one or more porous concrete inner walls (8) that extend into the inner volume (2) of the water tank (T), to split this inner volume at least in a rainwater / water storage space (3), and a buffer space (9) with a buffer volume to collect water that flows through the porous concrete inner wall (s) (8).

The buffer space (9) is provided with the outlet opening (5) for draining rainwater / water, while the porous concrete inner wall (s) (8) is / are made from a water-draining concrete with a maximum water permeability of 0.05 liters / m ² / s to 5 liters / m ² / s, preferably from 0.1 liters / m ² / s to 3 liters / m ² / s, more preferably between 0.1 liters / m ² / s up to and including 1 liter / m ² / s (such as 0.1; 0.2;

0.4; 0.5; 0.7; 0.8 and 1 liter / m ² / s), where the water permeability is measured at a water-rich storage space (3).

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Details and features of advantageous embodiments of the water tank according to the invention are one or more of the following:

- the water tank has a height of less than 3 m, more preferably between 1 and 2.5 m;

- in its first embodiment (Fig. 1) the total water discharge capacity varies linearly with the water level present between 0% and 100%,

- in a second embodiment, the total water drainage capacity measured at water height of half the storage space, and preferably at a water height of 0.3 m, is equal to 80% to 100%, preferably 90% to 100 % of these measured at an almost water-rich storage space (3);

- the porous concrete has one or more zones with increased water permeability with respect to the average water permeability of the porous concrete, wherein that zone or zones (10) are located at a height (h) from the bottom (3B) of the storage space ( 3) which is smaller than 50 cm, and preferably smaller than 30 cm. In this way it is possible to better regulate the drainage of rainwater.

At normal rain intensities, the water that flows into the water tank is drained to the stream with a slight delay. In that case, the storage space is only partially used. In heavy rain showers, the storage space and the buffer space are almost full. The water flow that is discharged to the stream is virtually limited by the passage of the outlet opening (5). The storage area acts as the first means of regulating / regulating the rainwater flow to the stream, canal, canal, river, etc. As soon as that storage space is full, the buffer space then acts as an additional storage space and buffer for rainwater;

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- the volume ratio of storage space (3) / buffer space (9) is greater than or equal to 2, preferably greater than 5, and most preferably between 5 and 20;

- the porous concrete inner wall (s) (8) defines / define a porous surface (S) facing the storage space (3), the ratio of storage volume (3) in m ³ / porous surface (S) in m ² between 0.5 and 1.5;

- the outlet opening (5) for draining rainwater has a passage which is suitable for limiting the water discharge flow through that outlet opening (5) between 1 and 201iter / s and preferably to a maximum of 51iter / s (that outlet opening can optionally be provided with a valve or valve mechanism to limit the water discharge rate, for example to 1; 2; 3; 4; 5; 10 liters / s);

- the water tank is provided with at least two separate overflows (3A, 9A), namely a first overflow (3A) for the storage space (3) for draining rainwater as soon as the water level in the storage space (3) exceeds the level (H3A) of that first overflow (3A), and a second overflow (9A) for the buffer space (9) for draining rainwater as soon as the water level in the buffer space (9) exceeds the level (H9A) of that second overflow (9A);

- the first overflow (3A) lies at least partially at a level (H3A) that is below the lowest level (H9A) of the second overflow (9A). The two overflows can drain water to the same drainage pipe to a stream or river;

- the first outlet (3A) has a passage area that is larger than the passage area of the second outlet (9A);

- the porous concrete inner wall (s) (8) has / have an upper side (8B) that is at a level (H8B) that is higher than the

BE2018 / 0079 lower edge of the first outlet (3A) and the lower edge of the second outlet (9A). This is to prevent water from flowing above the top of the inner wall;

- at least one porous concrete inner wall (8) is movable and / or removably mounted relative to the water tank, whereby a lower edge (8B) of the inner wall can rest on the bottom of the water tank (T). This is advantageous for assembly and / or maintenance work;

- the water tank is provided with a removable lid with manhole;

- the water tank is provided with at least two separate buffer spaces, namely at least a first buffer space (90) which is located along the bottom of a storage space (3), said first buffer space (90) collecting water from the storage space (3) via a at least partially horizontal porous concrete wall (80), and at least a second buffer space (9) cooperating with a vertical porous concrete wall (8) to collect water from the storage space (3), and characterized in that the first buffer space (90) and the second buffer space (9) are connected by a tube or channel (100), which is preferably located along the bottom of the water tank;

- said first buffer space (90) and second buffer space (9) are connected by means of a tube or channel (100) to an upper edge (100A) which has a slope with respect to a horizontal plane, so that said upper edge (100A) the direction to the second buffer space (9) rises;

- the water tank (T) has at least two separate storage spaces (3.30), said two separate storage spaces (3.30) being connected via a transfer tube (31) intended for carrying water from a first storage space (3) to a second storage space (30), as soon as the first storage space (3) is substantially water-filled, the second storage space (30) being provided with an overflow (3A) located at a level below the overflow tube (31);

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- the inlet opening (4) is provided with a system whereby, if the rainwater flow that flows into the tank through the inlet opening (4) is smaller than a certain flow, the system is adapted to directly discharge at least a part of the rainwater flow to enter to the buffer space;

- combinations of two or more of these details and characteristics.

The invention also relates to the use of several water tanks according to the invention for regulating water flows and / or water levels in streams and / or rivers and / or canals and / or flood areas by regulating / controlling drainage flows of rainwater from roofs, driveways and road requirements and / or water originating from a canal, stream, canal or river, wherein rain water and / or water flows to storage spaces of water tanks according to the invention, and wherein this rain water and / or water flows through porous concrete walls of the water tanks to buffer spaces before being transported to streams and / or rivers and / or canals and / or flood areas.

Specific embodiments of the invention will now be described as advantageous examples of the invention. Reference is made in the description to the accompanying drawings.

In those drawings, show:

Fig. 1 is a top view of a first embodiment of a water tank according to the invention,

Fig. 2 shows a view of the water tank of Fig. 1 in section along the line II-II,

Fig. 3 shows a top view of a second embodiment of a water tank according to the invention,

Figs. 4 to 6 are cross-sectional views of the water tank of Fig. 3, along lines IV-IV, V-V and VI-VI,

Fig. 7 is a view of a detail of the water tank of Fig. 3,

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Fig. 8A and Fig. 8B are views of a detail of an inlet opening for a water tank according to the invention,

Fig. 9 is a view of two water tanks connected together by pipes,

Fig. 10 shows a view in vertical section of a third embodiment according to the invention,

Fig. 11 is a sectional view along the line XI-XI in Fig. 10,

Fig. 12 is a top view of a fourth embodiment that is similar to the embodiment of Fig. 3,

Fig. 13 is a sectional view along the line XIII-XIII in Fig. 12, and

Fig. 14 is a view of a part of an inspection path along a canal or canal, with a series of water tanks according to the invention.

Fig. 1 shows a water tank (T) for collecting rainwater. That water tank includes:

- one or more outer walls (1) made of non-porous concrete and defining a tub with an inner volume (2), a part of which serves as a storage space (3) with a storage volume for rainwater;

- an inlet opening (4) through which rainwater can flow into the storage space (3);

- an outlet opening (5) for draining rain water from the water tank (T);

- a lid (6) with a manhole (7); and

- a control system (5,8) to control the drainage rate of rain water from the water tank (T).

The control system (5,8) consists of one or more porous concrete inner walls (8) that extend into the inner volume (2) of the water tank (T), to split this inner volume at least into a rainwater storage space (3), and a

BE2018 / 0079 buffer space (9) with a buffer volume to collect water that flows through the porous concrete inner wall (s) (8).

The buffer space (9) is provided with the outlet opening (5) for draining rainwater. That outlet opening is located along the bottom of the tub (T).

The porous concrete inner wall (8) is made with special draining concrete to obtain an adapted water permeability. The draining concrete has a minimum water permeability of 0.05 liters / m ² / s and a maximum water permeability of 0.1 liters / m ² / s to 5 liters / m ² / s, preferably of 0.1 liters / m m ² / s to 1 liter / m ² / s, such as 0.2 to 0.75 liters / m ² / s. The minimum water permeability is preferably from 0.2 to 0.5 liters / m ² / s.

The "maximum" water permeability of that inner wall is measured at a storage space (3) that is practically water-rich, while the buffer space is practically empty. For that measurement, for example, a pump is used to maintain the buffer space virtually empty.

One can also determine the maximum water permeability of the draining concrete by making a porous concrete slab that serves as the bottom of a test tub. The test tub (with a height equal to the height of the tank) will be filled with water afterwards, and the water flow will be measured for the water that flows through the porous bottom.

The draining concrete is preferably made by hardening a mixture of cement, aggregates and water, so as to preferably obtain a total open pore volume of 8 to 12% in the hardened concrete. For the concrete, aggregates with a particle size of 6 mm to 14 mm are preferably used. In general, the granules of the draining concrete contain 15% by weight of granules with a partial size larger than 8 mm, while the

BE2018 / 0079 water / cement weight ratio is less than 0.5, ideally between 0.35 and 0.42.

The uncured concrete mixtures (without water) contain less than 30% by weight of aggregates, better between 25 and 27% by weight, with a size of less than 4 mm.

The uncured concrete mixture (without water) can contain up to 15% by weight of sand, with a size smaller than 4 mm, for example with a size of 2 - 4 mm. The sand is preferably round-grain, and is, for example, a sand originating from a river. Examples of sand contents are 2; 5; 8; 10; 12 weight%.

In order to better control the water permeability of the concrete, one or more additives can be added to the uncured concrete mixture, such as aqueous polymer dispersion, in particular acrylate / methacrylate polymer / copolymer aqueous dispersion, such as copolymer of acrylic acid ester-vinyl ester aqueous dispersion. For example, 10 to 30% by weight of polymer dispersion can be added to the concrete, the percentage by weight being measured in relation to the cement weight.

The water tank has a height (H) of less than 3 m, such as from 2 to 2.5 m.

The height of the tank is better than lm.

In its first embodiment (Fig. 1), the total water discharge capacity varies linearly with the water level present between 0% and 100%.

In a second embodiment, the total water drainage capacity measured at water height of half the storage space, and preferably at a water height of 0.3 m, is equal to 80% to 100%, preferably 90% to 100% of this measured with an almost water-rich storage space (3).

BE2018 / 0079

Because of this property, you can better control the water that flows through the porous wall.

In the embodiment of Fig. 34, the porous concrete has a plurality of zones (10) with increased water permeability relative to the average water permeability of the porous concrete. Those zones (10) lie in the vicinity of the bottom, for example at a height (h) of the bottom (3B) of the storage space (3) that is smaller than 50 cm, and preferably smaller than 30 cm.

Those zones (10) can be manufactured by using aggregates with increased size. These zones can also form an intermediate layer in the porous wall, said intermediate layer being at a height between 20 and 50 cm relative to the bottom (3B).

The volume ratio of storage space (3) / buffer space (9) is greater than or equal to 2, preferably greater than 5, more preferably between 5 and 20.

The porous concrete inner wall (8) defines a porous surface (S) facing the storage space (3), the ratio of storage volume (3) in m ³ / porous surface (S) in m ² between 0.5 and 1, 5 (such as between 0.7 and 1.25, preferably 0.8; 0.9; 1; 1.1 and 1.2). This ratio provides a good control of the maximum flow of water that flows through the porous wall, and a sufficient storage volume for rainwater.

The outlet opening (5) for discharging rain water has a passage which is suitable for limiting the water discharge flow through said outlet opening (5) between 1 and 201 liters / s and preferably to a maximum of 51 liters / s.

The water tank is provided with at least two separate overflows (3A, 9A), namely a first overflow (3A) for the

BE2018 / 0079 storage space (3) for draining rainwater from the storage space, as soon as the water level in the storage space (3) exceeds the level (H3A) of that first outlet (3A), and a second outlet (9A) for the buffer space ( 9) for draining rainwater from the buffer space as soon as the water level in the buffer space (9) exceeds the level (H9A) of that second overflow (9A).

Via said overflows 3A, 9A, two water tanks T, T1 according to the invention can be bound together by pipes 20,21. The tank T1, for example, is located at a lower level with respect to the tank T, as a result of which water can flow freely from tank T to tank T1. The overflow opening 3A of the tank T is connected to the inlet opening 4 of the tank T1 via the pipe 20. As soon as the storage space 3 of the tank T is full, water flows from said storage space 3 to the storage space 3bis of the tank T1.

The inlet 9A of the buffer space 9 of the tank T is with an inlet 40 via the pipe 21. If the buffer space 9 of the tank T is almost full, then water flows from the buffer space of the tank T to the buffer space 9 of the tank. tank Tl. Via pipes 22, water is drained from the buffer spaces 9 from tanks T and T1 to the stream.

The first overflow (3A) is located at least partially at a level (H3A) that is above the lowest level (H9A) of the second overflow (9A).

The first outlet (3A) has a passage surface that is larger than the passage surface of the second outlet (9A).

With those overflows 3A, 9A, the water level in the buffer space 9 is always lower than the water level in the storage space 3, even in the event of a storm.

The porous concrete inner wall (8) has an upper side (8B) that lies at a level (H8B) that is higher than the lower edge of the first overflow (3A) and the lower edge of the second overflow (9A). This

BE2018 / 0079 is advantageous to prevent water from flowing over the inner wall of the storage space to the buffer space 9.

In the shown embodiment of Fig. 1, the cover 6 is removably mounted on the tub 1. In that case, it is also advantageous to mount the porous concrete inner wall 8 removably in the tub. The lower edge of the wall 8 rests on the bottom of the tub, possibly with a rubber intermediate piece.

Via the manhole 7, one can have a view of the water level in both rooms (3.9). Maintenance work can also be carried out through the manhole in the cockpit.

In the embodiment of Fig. 3, the water tank comprises three or more than three separate buffer spaces (9.90, 91), namely (a) at least one first and second buffer spaces (90, 91) which are along the bottom of a storage space (3) are located, said first and second buffer spaces (90) collecting water from the storage spaces (3,30) via an at least partially horizontal porous concrete wall (80,81), and (b) at least a third central buffer space (9) cooperating with two vertical porous concrete walls (8,8 bis) to collect water from the storage rooms (3,30).

The position of the porous walls 80,81 along the bottom of the tub can be maintained via fixing means (bars 111).

The first and second buffer spaces are connected to the third buffer space (9) by pipes (100) located along the bottom of the water tank. Those tubes 100 show a slope with respect to a horizontal plane, as a result of which the upper edge (100A) of those tubes rises in the direction of the third buffer space (9). In this way it can be prevented that air or gas remains in the buffer spaces 90, 91, which can be disadvantageous for the passage of water.

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The two separate storage spaces (3.30) are connected via a transfer tube (31). That tube 31 is intended for discharging water from the first storage space (3) to the second storage space (30), as soon as the first storage space (3) is substantially water-filled, the second storage space (30) being provided with a drain (3A) ) which is located at a level below the transfer tube (31).

In a possible embodiment, the inlet opening (4) can be provided with a control system 100, whereby if the rainwater flow flowing into the tank T is smaller than a certain flow, the system 100 is adapted to directly transfer at least a part of the rainwater flow to be discharged to the buffer space 9. With such a system, for a short and non-stormy rain period, the rain water can be partly discharged to the storage space 3, as well as partly to the buffer space.

Such a system is shown in figures 8A and 8B. The rainwater W flows into a chamber 101 which is provided with an open inner vessel 102 to collect at least a part of the rainwater. The bottom of this vessel is provided with a hole 102A. Within this vessel, a float 103 moves with a surface 103A that acts as a valve system. The inner vessel 102 is in communication with an inlet opening 40 of the buffer space 9, via a pipe 41.

For small water flows W, the water flows into the inner vessel 102. Since the flow rate is not sufficient, the float 103 remains in a lower position, as a result of which part of the rain flows directly to the buffer space 9, while another part flows to the storage space 3 via the opening 102A. (see Fig 8A).

In the event of a rainstorm, the water level in the inner vessel rises, whereby the float 103 is in the closed position, to seal the inlet of the pipe 41. In this closed position, almost all the rain flows into the storage space of the tank T.

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A third embodiment of a water tank according to the invention is shown in FIG.

The tank T comprises a concrete tub (watertight) with an outlet 5 along the bottom 1B. Along the bottom IB, the tank is provided with one or more supporting elements 1C for a plate 80 of porous concrete. The round plate 80 supports itself or the supporting elements 1C. Above the plate 80 there is cylindrical pipe 82 made of porous concrete.

The plate 80 can optionally be provided with a hole 80G to connect the buffer zones 9,90 together. If that plate 80 is not provided with the hole 80G, the buffer spaces are connected via the open pores of the plate 80.

The cylindrical pipe 82 can preferably be placed in the tank via the manhole 7. The correct placement of the pipe can be obtained via intermediate elements 110 which are situated between the upper edge of the pipe 82 and the lower surface of the cover.

Figures 12 and 13 are views of an embodiment similar to the embodiment of Figures 3 to 6, unless a few modifications.

The tub and / or the vertical porous walls 8, 8 bis are provided with support elements 1C for porous plates 80, 81. The position of the plates on the support elements 1 C is maintained by the use of fastening means 111, which are, for example, partially in a wall of the tub stung.

Fig. 14 is a view of a moat or canal 200, with a dam 201 and two inspection paths 202,203. Along the inspection path 203, several water tanks have been installed according to the design. The water tank 1 is in communication with the channel 20 via the pipe 204. The storage spaces of the water tanks 1, Ibis, 1b, etc. are in communication, so that water can be discharged from the storage space of tank 1 to

BE2018 / 0079 the storage space of tank Ibis, as soon as the water level in storage space 3 of tank 1 exceeds a certain level.

The outlets 5 of all tanks 1, Ibis, etc. are connected to an outlet pipe 205 to drain water back into the channel, after the dam 201.

The water tanks according to the invention can thus be used to control the water level in the channel. As soon as the water level exceeds a maximum level, the water tanks 1, Ibis, etc. can collect water from the channel, and be discharged back into the channel with a delay, which is a solution against storm water (with heavy rain in a short time).

Since the water tanks can be located under inspection paths, the construction of those tanks can be carried out with the installation of those inspection paths.

BE2018 / 0079

CONCLUSIONS

A water tank (T) for collecting rainwater / water, the water tank (T) comprising at least:

- one or more outer walls (1) made of non-porous concrete and defining an inner volume (2), a part of which serves as storage space (3) with a storage volume for rainwater / water;

- an inlet opening (4) through which rainwater / water can flow into the storage space (3);

- an outlet opening (5) for draining rainwater / water from the water tank (T);

- a lid (6) with a manhole (7); and

- a control system (5,8) for controlling the discharge rate of rainwater from the water tank (T), characterized in that the control system (5,8) consists of one or more porous concrete inner walls (8) that extend into the inner volume (2) of the water tank (T), to split this inner volume at least into a rainwater / water storage space (3), and a buffer space (9) with a buffer volume to collect water flowing through the porous concrete inner wall (and ) (8), characterized in that the buffer space (9) is provided with the outlet opening (5) for draining rainwater / water, and characterized in that the porous concrete inner wall (s) (8) is / are manufactured from a water-draining concrete with a maximum water permeability of 0.05 liters / m ² / s to 5 liters / m ² / s, preferably from 0.1 liters / m ² / s to 3 liters / m ² / s, more preferably between 0.1 and

Claims (17)

1 liter / m ² / s, where the water permeability is measured at an almost water-rich storage space (3). Water tank according to claim 1, which has a height (H) of less than 3 m, characterized in that the total water drainage capacity measured at water height of half the storage space, and preferably at a water height of 0.3 m, is equal to 80% up to 100%, preferably 90% to 100% of these measured at a substantially water-rich storage space (3). Water tank according to claim 1 or 2, characterized in that the porous concrete has one or more zones with increased water permeability relative to the average water permeability of the porous concrete, wherein said zone or zones (10) is / are at a height ( h) from the bottom (3B) of the storage space (3) that is smaller than 50 cm, more preferably smaller than 30 cm. Water tank according to one of the preceding claims, characterized in that the volume ratio of storage space (3) / buffer space (9) is greater than or equal to 2, preferably greater than 5, and most preferably between 5 and 20. Water tank according to one of the preceding claims, characterized in that the porous concrete inner wall (s) (8) defines / defines a porous surface (S) facing the storage space (3), the ratio of storage volume (3) in m ³ / porous surface (S) in m ^{2 is} between 0.5 and 1.5. Water tank according to one of the preceding claims, characterized in that the outlet opening (5) for draining rain water has a passage which is suitable for limiting the water discharge flow through said outlet opening (5) between 1 and 201 liters / s and at preferably up to a maximum of 51 liters / s. Water tank according to one of the preceding claims, characterized in that the water tank is provided with at least two separate ones BE2018 / 0079 overflows (3A, 9A), namely a first overflow (3A) for the rainwater storage space (3) as soon as the water level in the storage space (3) exceeds the level (H3A) of that first overflow (3A) and a second overflow (9A) for the buffer space (9) for draining rain water as soon as the water level in the buffer space (9) exceeds the level (H9A) of that second overflow (9A). Water tank according to the preceding claim, characterized in that the first overflow (3A) lies at least partially at a level (H3A) that is below the lowest level (H9A) of the second overflow (9A). Water tank according to the preceding claim, characterized in that the first overflow (3A) has a passage surface that is larger than the passage surface of the second overflow (9A). Water tank according to one of claims 7 to 9, characterized in that the porous concrete inner wall (s) (8) has / have an upper side (8B) that is at a level (H8B) that is higher than the lower edge of the first outlet (3A) and the lower edge of the second outlet (9A). Water tank according to one of the preceding claims, characterized in that at least one porous concrete inner wall (8) is movably and / or / and removably mounted relative to the water tank, wherein a lower edge (8B) of the inner wall is on the bottom of the water tank (T) can rest 12. Water tank as claimed in any of the foregoing claims, characterized in that the water tank is provided with a removable lid which is provided with a manhole. Water tank according to one of the preceding claims, characterized in that the water tank is provided with at least two separate buffer spaces, namely at least a first buffer space (90) which BE2018 / 0079 is located along the bottom of a storage space (3), said first buffer space (90) collecting water from the storage space (3) via an at least partially horizontal porous concrete wall (80), and at least a second buffer space (9) cooperating with a vertical porous concrete wall (8) for collecting water from the storage space (3), characterized in that the first buffer space (90) and the second buffer space (9) are connected by a tube or channel ( 100), which is preferably located along the bottom of the water tank. Water tank according to the preceding claim, characterized in that said first buffer space (90) and second buffer space (9) are connected by means of a tube or channel (100) with an upper edge (100A) having an inclination with respect to a horizontal plane through which said upper edge (100A) rises in the direction towards the second buffer space (9). Water tank according to claim 13 or 14, characterized in that the water tank (T) has at least two separate storage spaces (3.30), said two separate storage spaces (3.30) being connected via a transfer tube (31) intended for passing water from a first storage space (3) to a second storage space (30), as soon as the first storage space (3) is substantially water-rich, the second storage space (30) being provided with an overflow (3A) which is at a level is located below the transfer tube (31). A water tank according to any one of the preceding claims, characterized in that the inlet opening (4) is provided with a system whereby, if the rainwater flow rate flowing into the tank through the inlet opening (4) is smaller than a certain flow rate, the system is appropriate is to discharge at least a part of the rainwater flow directly to the buffer space. Use of a plurality of water tanks according to any one of the preceding claims for regulating water flows and / or water level in streams and / or rivers and / or canals and / or flood areas by regulating discharge flows of BE2018 / 0079 rainwater from roofs, driveways and road requirements and / or water from a canal, stream, canal or river, wherein rainwater and / or water flows to storage spaces of water tanks according to one of the preceding claims, and wherein this rainwater and / or water 5 flows through porous concrete walls of the water tanks to buffer spaces thereof, before being transported to streams and / or rivers and / or canals and / or flood areas.