Advice, questions and answers


Advice, questions and answers

Technical assistance

Our engineers are on hand with advice regarding the dimensioning and installation of a BIO-BLOK® rainwater drywell.

The advice is of course free and non-binding.

The advice also covers recommendations and guidance for larger residential areas which require integrated seepage solutions and/or retarding basins, which may include green solutions with wetlands and planted open retarding basins.

If you are facing this type of challenge and need inspiration for your project you are always welcome to contact us.

Enquiries can be made to:

EXPO-NET Danmark A/S
Georg Jensens Vej 5
DK-9800 Hjørring

Phone: +45 98 92 21 22
Fax: +45 98 92 41 89

E-mail: assistance(at)

Questions and answers in connection with installing a BIO-BLOK® drywell

Q: Which fibre cloth is recommended?
A: We recommend Byggros’ geotextile type DuPont Typar or an equivalent product. It is important to use a fibre cloth which can keep soil and sand out and which also allows water to seep through.

Q: Is it always possible to replace a stone drywell with a BIO-BLOK® drywell?
A: Yes, as long as you follow the applicable dimensioning rules.

Q: How does the BIO-BLOK® drywell clean the rain water?
A: BIO-BLOK® was originally developed for cleaning wastewater. The block is constructed as a net tube so that the block has a large surface area per cubic metre of block. The effectiveness of the cleaning depends on how large a surface is per cubic metre of BIO-BLOK®. Nature will take care of the rest with an organic breakdown of the added wastewater.

Q: What does the vertical contact surface mean for the effectiveness?
A: The vertical contact surface is twice the length of the height. The higher the vertical contact surface, the more effective it will be. This is why BIO-BLOK® elements are halved if the soil conditions are tough. The bottom area is not included when sizing.

Q: What happens when a BIO-BLOK® is halved?
A: The vertical contact surface increases significantly, which means the capacity is also higher. Generally speaking, the capacity can be increased by approx. 20% or the drywell's total volume can be reduced by 20%.

Help with tender text

The drywell is manufactured as a BIO-BLOK® drywell or equivalent. The surface area per cubic metre must be a minimum of 80 m2. The drywell is made of welded vertical net tubes produced in the imperishable material polyethylene with a modular size (W x L x H) of approx. 54 x 54 x 55cm.