Find the answers to frequently asked questions about Rockflow in the FAQ overview. Is your question or answer not listed? Then use the search engine at the top of the website or contact the Rockflow team.
Rockflow in general
Rockflow in general
Sustainability & circularity
Maintenance & service life
Rockflow in general
What is the maximum installation depth of Rockflow?
The maximum depth of a Rockflow buffer is determined by the highest local groundwater level. In order to be able to infiltrate with a Rockflow buffer, the bottom of the buffer must be installed above the highest groundwater level. The groundwater level should preferably be measured on site. Is this not possible? Then request the readings from the respective municipality. Other factors determining the maximum installation depth are soil and surface use on top of the buffer. Please contact the Rockflow experts to learn more.
What is the minimum coverage required for Rockflow?
Among other things, the high density of the Rockflow stone wool elements ensures a large load-bearing capacity, which means that minimal cover is required. In many cases, the cover consists of mixed granulate. The exact degree of coverage is stated in the Rockflow installation manual.
Does stone wool absorb water from the overlying ground?
No. Because soil and substrate have a higher suction pressure than stone wool, no water is extracted from the soil or substrate.
What is suction pressure?
Suction pressure is a characteristic of the water absorption capacity. Among other things, this is determined by the capillarity and the amount of water present in the material. In the case of soil and substrates, this suction pressure is always higher than that of stone wool. Stone wool therefore cannot extract water from the ground.
What is the density of Rockflow?
Among other things, the density of Rockflow ensures a high load-bearing capacity. The basic material is stone wool, which has all the properties of stone. Vehicles can park on top of the system without the elements losing their shape or functionality.
Rockflow is available in various densities. The most commonly used density is 5%. The remaining 95% is therefore available for the absorption of rainwater.
What is Rockflow’s emptying time?
Rockflow stone wool has an outflow speed of 100 metres/24 hours. Taking into account the k-value of the substrate, a system is always designed to be completely empty and available again 24 hours after a shower. If this is not achieved due to a low k-value, the system is designed to undergo sufficient deflation via a delayed discharge (pinch construction).
Thanks to the large infiltration surface of stone wool, infiltration even on poorly permeable soil types such as clay is an option. Water absorption and release in stone wool remains the same throughout the product’s lifetime. In the event of unforeseen events such as flooding, the system can also be completely cleaned.
A swale is a water-permeable buffer that fills up with water in the event of rainfall and discharges it to the ground. A swale is often a ditch or trench with a water-permeable base.
A traditional swale usually consists of a layer of soil with plants. The swale collects the rainwater, and slowly releases it into the ground. But because the space is often limited, a swale must be relatively deep in order to be able to collect sufficient rainwater. A Rockflow infiltration system can be installed beneath the layer of earth and plants, thereby creating more space for the collection of water. Thanks to the stone wool elements, a swale containing Rockflow stone wool is also shallower than the traditional variant.
The permeability of the soil is expressed by the k-value, also known as permeability or hydraulic conductivity. A k-value of 1 means that a raindrop travels 1 metre in a 24-hour period. The k-value is an important value, as it maps out the permeability of an infiltration facility.
The k-value of Rockflow stone wool is 50 to 200 metres per 24 hours, depending on the type of stone wool used. The k-value of the Rockflow water management system is therefore comparable to that of coarse sand or fine gravel.
Does stone wool cause irritation?
Although stone wool is a safe material, temporary irritation (itching) may occur when working with it. To minimise this, we recommend that you always take the following measures when working with stone wool products outdoors:
Wear body-covering clothing (long sleeves and gloves);
There is currently no CE mark for Rockflow stone wool, partly because the combination of stone wool and water management is not yet standardised. Rockflow is expected to have the CE mark and Declaration of Performance in 2023.
Is it possible to place playground equipment above a Rockflow buffer?
Yes, objects such as playground equipment can be placed above a Rockflow buffer. Please note: the buffer must not be damaged during installation and the forces of the devices must be well distributed over the surface. Please contact the Rockflow team for the specific installation.
How quickly is water distributed in the Rockflow system when it enters the stone wool via the water channels?
The permeability of Rockflow stone wool is approx. 100m/24 hours. Rockflow systems are always designed so that every system, regardless of its size, is completely filled within 8–10 minutes. The upstream supply is often the limiting factor rather than the water permeability of the stone wool itself. This principle remains the same for larger systems with multiple input channels.