Function and installation

How many Hydrorock infiltration blocks do I need?

The number of required Hydrorock® blocks depends on the surface, the groundwater level and the soil type. Use our calculator to calculate how many blocks you need. Our calculator for disconnecting rainwater can be found here. Look here for solutions to prevent flooding

Why is the use of Hydrorock dependent on the soil type?

The speed with which Hydrorock absorbs blocks of water depends on how the water can reach the blocks.

To allow rainwater to penetrate the soil, it must be sufficiently permeable. The groundwater level also influences the infiltrating effect. The closer the density of the soil type, the slower infiltration takes place and therefore the more infiltration blocks you need.

If water comes in direct contact with the blocks, the speed at which the blocks can absorb the water is approximately 400 liters per m2 per minute. If water reaches the blocks via a less porous soil type, this has a delaying effect and is then also decisive. Use our calculator to calculate how many blocks you need for your soil type. Our calculator can be found here.

Can Hydrorock be used with high groundwater levels?

The infiltration blocks must always remain above groundwater level. The blocks would otherwise be filled with groundwater instead of surface water. Therefore, always check the groundwater level before you start construction. Local groundwater monitoring networks or the DINO counter (Data and Information from the Dutch Subsurface) can help you with this. At a high groundwater level, it is possible to work with blocks that have a lower height, such as the types D34 or D112.

How are the infiltration blocks placed?

Hydrorock blocks have a fine-grained fiber structure in one direction. A horizontal fiber direction promotes a drainage function. A vertical fiber direction promotes an infiltrating function. Due to the load-bearing capacity of the blocks, these must always be positioned in a vertical position for buffering and infiltrating action (the sticker with the text "this side up" is then on top). If bearing capacity is of secondary importance, the blocks can also be used horizontally for drainage purposes of surface and rainwater. For optimum drainage, we recommend placing the blocks one behind the other and in a horizontal position (lying down). You will find the placement instructions in the here.

How are the Hydrorock blocks connected to each other?

One of the strengths of Hydrorock® is that each block has its own buffer, drainage and infiltration function. Depending on the size of the desired buffer function and soil type, several blocks are placed next to and behind each other. The blocks then transfer the water to each other. Use type BD for connection to rainwater drains.

How are Hydrorock blocks connected to rainwater discharge or street drain?

The connection to the rainwater drainage is done by connecting the rain pipe to the Hydrorock blocks of type BD. This version has a perforated tube (ø 100mm) that runs through the block so that the water can run into the block. The tube can be connected to rainwater drains, street vents, pipes, drainage hoses, gutters, etc. These blocks can be mutually coupled in the longitudinal direction by means of a small piece of perforated tube. The buffer capacity can be increased by placing a type D block without tube on the side (s) of type BD. The blocks pass the water on to each other.

What is the water absorption capacity of the infiltration blocks in terms of time?

The speed with which Hydrorock blocks blocks of water depends on how the water can reach the blocks. If water comes in direct contact with the blocks, the speed at which the blocks absorb the water is approximately 400 liters per m2 per minute. If water reaches the blocks via a porous layer of, for example, sand, then sand has a delaying effect in this case and is then also normative. The absorption capacity / permeation speed of porous sand is approximately 50/60 liters per hour, which means that 50 liters of water on an area of 1 m2 takes 1 hour to sink into this. Absorption of water via the perforated tube in type BD blocks proceeds at a speed of 100 liters per linear meter of tube per minute.

What is the permissible load / carrying capacity?

The permissible load of the standard Hydrorock infiltration blocks type D is 75 kg per m3. For the High Density version type HD, the standard load capacity is 120 kg per m3. For extra heavy loads, there is an XHD variant with a load capacity of 160 kg per m3. The infiltration solutions can be designed for various strengths on these three Hydrorock variants. Depending on the type of stone wool and the soil conditions, the typical installation depths for the various traffic classes are shown here.

Can the Hydrorock blocks be cut to size without losing their functionality?

The Hydrorock blocks are supplied as standard in fixed dimensions but sawing the blocks to size is fairly simple. Of course, the blocks do not lose their effect as a result. Care should only be taken to ensure a good seal with the filter cloth. You can proceed as follows:

  1. Use a cutting knife and cut the filter cloth a few centimetres from the side around it on, starting on the side (the side where the sticker is placed).
  2. Cut the fabric on top, then on the other side and then the bottom (the folding seam is the bottom).
  3. You now have a type of cap. Remove this cap from the block.
  4. Now cut the desired size of the block with a wood saw.
  5. After this, slide the cap over the filter cloth again overlapping.

The infiltration block has now been shortened to the desired size and the filter cloth is again enclosed around it.

Do I need fall for correct drainage?

Unlike drainage hoses, Hydrorock blocks do not require a slope for correct drainage. The unique stone wool material ensures that it does not matter how the infiltration blocks are placed. By placing the infiltration blocks behind each other (possibly in various directions) the optimum drainage function is created. In this way, they always function as rainwater buffers and release the absorbed water to the surrounding soil.

Is Hydrorock resistant against erosion by plant- and tree roots?

Hydrorock is produced from stone wool, a 100% natural material. It remains underground for decades in optimum condition. Hydrorock is resistant to erosion by plant and tree roots and will continue to function well for years. The cotton-based membrane of filter cloth does not mold or rot. It has a high breaking strength and is resistant to the natural substances in the soil. Stone wool is 100% recyclable. Flora and fauna thrive excellently on Hydrorock.

Should the brackets be screwed to the linear channel drain?

No, the linear and brackets work according to a handy click system, which makes screwing unnecessary.

How many brackets are needed for the linear channel drain?

When placing a linear channel drain, account must be taken of placing the linear channel drain brackets between the transition from block to block. For 3 blocks, therefore, 2 brackets are required. The linear channel drain and brackets work according to a handy click system, making screws unnecessary. Look for the schedules and accessories here.

Hydrorock International also supplies infiltration blocks with integrated linear channel drains. This type (LG34 and SL55 in various designs, see has been specially developed for consumers and works according to a handy click system.


How much maintenance does the Hydrorock system require?

If the blocks are positioned correctly, the system requires no maintenance. Unlike other solutions, running in of soil is not possible in this system. The blocks therefore do not need to be inspected or cleaned. When uncoupling rainwater discharges it must be prevented that dirt blocks the pipes. This is easy to do by placing a foliage and sand catcher. These systems are easy and quick to clean. If there is a wish to still be able to clean the system extra, we advise you to install the uncoupling system in a loop. In this way the system can be sprayed through and therefore easy to clean should there still be some dirt blockage.

Prices and warranty

What is the warranty on Hydrorock products?

The warranty on Hydrorock products applies for a period of 10 years whereby the manufacturer guarantees performance, shape retention and functionality. Warranty is applicable if these requirements and methods are adhered to:

  • The water absorption, the absorption capacity of the blocks remain between 88% and 94% of the block volume;
  • The water delivery to the soil, if the conditions have remained unchanged;
  • The carrying capacity;
  • The shape retention;
  • The composition of the product.
Where can I find the Hydrorock price overview?

For the most current prices, we advise you to contact your nearest Hydrorock International dealer. Look here for an overview of suppliers of Hydrorock solutions. They will be happy to make a customized offer for you. For prices and online ordering of individual Hydrorock® products you can look at the various web shops.

What guarantee does Hydrorock International provide on its products?

At the Hydrorock International B.V. products a guarantee period applies for a period of 10 years in which the manufacturer guarantees operation, dimensional stability and functionality. Also keep in mind that the performance of the product in a structure or system is highly dependent on the parameters of such structure or system, such as (but not limited to) local soil conditions, the quality of the installation and other components. All these parameters fall outside the sphere of influence of Hydrorock International B.V. Consequently, Hydrorock International B.V. offer no guarantee regarding the performance of the product.
For a complete overview of all specifications, please refer to our Product Data Sheet with references from Deltares, among others.


Is Hydrorock also available in other countries?

Certainly, Hydrorock works with professional retailers in many countries. We are more than happy to refer you to one of these retailers. Hydrorock also works together with authorised retailers outside Europe. In China, Hydrorock is used to collect rainwater from highways, for example. Our official retailer in Australia sells Hydrorock mainly to prevent desiccation.

Where are Hydrorock products available?

Hydrorock International has professional dealers in many countries. We are happy to link you to one of these points of sale. Hydrorock International also has official dealers outside Europe. In China, for example, Hydrorock is used to collect rainwater from highways. In Australia our official dealer sells Hydrorock primarily to prevent drying out. View all our current points of sale here.

Is the Hydrorock International range also available for consumers?

Hydrorock has a special product line for private individuals under the brand name Hydroblob®. There is an extensive dealer network for this range. There is usually a point of sale in your area. View our special Hydroblob website for more information.

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