The Stormbloc® Optimum range of geocellular storage and infiltration blocks
Posted - 21 August 2023

We answer your common questions on our Stormbloc Optimum range

In this blog our Technical Team Manager, Chui Green answers some common questions about the extended Stormbloc® Optimum range.

Earlier this year, we expanded our Stormbloc® range, a geocellular system providing underground storage and infiltration of surface water runoff to help prevent flooding as part of Sustainable Drainage Systems (SuDS).  

Since we expanded the range with our new product, we have received some similar questions – from the differences between the two models and where they should be used, to maintenance and monitoring. 

Well, we are here to help! 

Let’s start from the beginning. What are the differences between the two models in the range?  In a nutshell, the new Stormbloc® is a lighter system which is ideal for installation in a broad range of schemes, especially lightly trafficked and landscaped areas, such as residential areas. 

In comparison, the Stormbloc® Extra is a high-strength block designed for heavily loaded areas, such as roads and car parks, or for installations up to 4m in depth.  

Both Stormbloc® and Stormbloc® Extra can save time and cost at installation, with the ability to stack the blocks into compact nests for storage and transportation, and enabling more storage volume in one place at any time.  Both work well with a Hydro-Brake® Optimum downstream to optimise the storage volume and control the runoff from a site.

Developed by our polymer specialist partners, REHAU, what makes them similar is that both the Stormbloc® and Stormbloc® Extra are completely customisable, with the length, width, and height all adaptable to meet even the most demanding of drainage designs. They can also both be accessed for inspection and maintenance, and both have the same 96% storage capacity.  So, even for the most complex of projects, we can help!

Which one is best for your project?

Other common questions we have been asked are around planning and installation, and how you know which one is best for your project.  It’s always best to speak to one of our design team if you are unsure, but the following should also help.   

Stormbloc® can only be used beneath car parks and amenity areas if the total loading is 2.5 tonnes or below – for anything higher, Stormbloc® Extra would be more suitable, or a bespoke design via our design team.

The maximum storage volume for a single Stormbloc® element (800 mm x 800 mm x 300 mm) is 0.203 m3, whilst the storage volume for the base plate (800 mm x 800 mm x 30 mm) is 0.017 m3. The total excavation depth cannot exceed 3 metres in depth when using Stormbloc® (six blocks deep), so if the area needs to be deeper, you should use Stormbloc® Extra as it is able to withstand the additional loadings up to a depth of 4 m.  

If your design depth is greater than 3 m for Stormbloc® or 4 m for Stormbloc® Extra, please contact the design team as this can often be achieved with a bespoke design. 

The minimum cover level for a Stormbloc® or Stormbloc® Extra installation depends on the loading that the tank will be subject to. These are listed in the tables below.

Stormbloc® design parameters table.
Stormbloc® Extra design parameters table

Monitoring and maintenance made easy

We have also had a few questions around maintenance and monitoring, and the good news is that we have made it really easy with the Stormbloc® system!

Adding Stormbloc® Inspect chambers and constructing a row of Stormbloc® Extra blocks through the tank will provide convenient access for inspection and maintenance of Stormbloc® tanks. If your system does not include a Stormbloc® Inspect Chamber or high-level pipe, a ventilation plate is available too.  

Stormbloc® tank with Stormbloc® Inspect and Stormbloc® Extra row for inspection & maintenance access

You could also consider providing pre-treatment upstream of the system to stop the build-up of solids settling in the system.  Our Downstream Defender® Select is ideal for this as it removes a range of pollutants including, fine and coarse sediments, floating debris and hydrocarbons.

To take it to the next level, you can also integrate Hydro-Logic® Smart Maintenance technology, which allows remote monitoring to provide real-time insight into water levels. This clever system will send automated alerts when the Stormbloc® system needs cleaning or if a blockage occurs. Data captured by the Hydro-Logic® Flexi Logger and sensors enable you to forecast future maintenance requirements and develop cost-effective maintenance plans.

CCTV inspection, maintenance and cleaning are also all possible, but we would always recommend a scheduled maintenance routine that is completed at least once a year.

That wraps up our most common questions, but if you have any others we haven’t answered here, we would be happy to help.

Email the team at and check out our full FAQs and other resources here

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Downstream Defender® Select working with Stormbloc® Optimum, Hydro-Brake® Optimum and Up-Flo™ Filter

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