Stormbloc Optimum range July 2025
Flow control and flood protection

Stormbloc Optimum range

Download the brochure

Attenuate or infiltrate surface water and stormwater effectively even in challenging high-traffic urban environments.

The Stormbloc® Optimum range comprises four resilient geocellular storage systems that provide underground storage and infiltration of surface water runoff. Stormbloc® LT, Stormbloc® MX, Stormbloc® SX and Stormbloc® HX, plus an inspection chamber, the Stormbloc® Inspect.


The lightweight materials, combined with robust design make them easy to transport, quick to install and extremely durable.  With an optimum-strength option for high-traffic areas and a lighter option for landscape and low-traffic areas, the Stormbloc® Optimum range provides a space-saving solution for many applications.

The Stormbloc® Optimum range is modular and easily customisable, giving engineers the freedom to configure storage for even the most challenging SuDS project.

Download our white paper:  Tips for trouble-free geocellular design

The Stormbloc® Optimum range is a below-ground stormwater storage or infiltration system that includes a choice of four robust geocellular storage blocks which range in strength from Stormbloc® LT, for use under green and landscaped areas with light traffic, up to Stormbloc® HX, a very high strength block which can withstand frequent loadings of up to 60 tonnes.  

The system helps meet Sustainable Drainage System (SuDS) objectives by returning stormwater back to the natural water cycle at or near its source, without taking up valuable space for amenity or development above ground.


Applications

•    New and retrofit Sustainable Drainage (SuDS) schemes.
•    Infiltration / soakaway schemes.
•    Attenuation schemes.
•    Highways and infrastructure projects.
•    To increase swale / pond capacity.
•    Car parks and Park & Ride schemes.
•    Housing Developments.
•    Schools and Public / Civil schemes.
•    Aquifer re-charge.
•    Storage for rainwater harvesting and re-use

Stormbloc® LT

A lighter, cost-effective option suitable for landscaped lighter traffic areas, up to 3 m in depth.  Access for inspection and maintenance can be included where required using Stormbloc® Inspect chambers and Stormbloc® SX blocks.

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Stormbloc® storage/infiltration block

Stormbloc® MX

A new medium-strength option with a maximum installation depth of 3 m.  Suitable for mid-range traffic loading such as car parks, bus lanes, pedestrian zones with delivery traffic, access roads to residential complexes and clinics. up to 3 m in depth.  

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Stormbloc MX

Stormbloc® SX

A high-strength option ideal for installation beneath heavily loaded and high-traffic areas, up to  4 m in depth.  Suitable for heavily loaded and high-traffic  areas such as residential and service roads and access roads in industrial are commercial car parks (cars and lorries), lorry loading bays, warehouse yards.  Access for inspection and maintenance is via Stormbloc® Inspect chambers and the channels in the blocks allow access for CCTV and cleaning to ensure that the storage volume of the system isn’t reduced by the build-up of silts.

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Stormbloc® Extra

Stormbloc® HX

A very strong block which can be installed up to 6 m in depth.  Ideal for very heavily loaded areas such as residential and service roads, and access roads in industrial and commercial car parks (cars and lorries), lorry loading bays, warehouse yards.

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Stormbloc HX

Stormbloc® Inspect

The Stormbloc® Inspect offers an unrivalled level of accessibility to any Stormbloc® LT or Stormbloc® SX/MX/HX installation. This modular access chamber, sited within the tank, has identical dimensions to a Stormbloc® SX/MX/HX module and so can be easily incorporated into the layout of the infiltration or storage system.

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Stormbloc® Inspect chamber

The Stormbloc® Optimum range is only available in the UK and Ireland

 

Maximise storage

The Stormbloc® Optimum range can store 960 litres of stormwater below ground in 1 cubic metre of volume, more than 60% more stormwater storage in the same volume when compared to conventional gravel infiltration trenches.

Customise your storage

Length, width and depth of storage can be customised in order to meet even the most demanding of drainage environments.  Options for high- and low-traffic loading and shallower or deeper installations enables cost-effective storage designs.

Save space on site

All the Stormbloc® Optimum range blocks stack into compact nests for transport and storage, saving up to 75% of valuable space. The nested units save time and cost during installation, enabling more storage volume to be lifted into excavations at any one time.

Lightweight with four strength options

For more flexible designs choose between the high-strength Stormbloc® HX for high-traffic and deep, Stormbloc® SX for high-trafffic installations and Stormbloc® MX and Stormbloc® LT for shallower installations with medium or lighter loads such as landscaped or low-traffic areas.

Stormbloc® LT

Length / width / height:  800 / 800 / 330 mm (note:  for the bottom layer add 30 mm for the base plate)

Constructed block weight:  10 kg (1 element and 1 base plate)

Nominal storage capacity per unit:  0.220 m3

Porosity: 96%

Vertical ultimate compressive strength:  320 kN/m2

Horizontal ultimate compressive strength:  100 kN/m2

Cover level (landscaped area, no traffic):  ≥0.5 m

Cover level (light traffic loading ≤ 3 tonnes* ):  ≥0.8 m

Maximum installation depth:  3 m

*Occasional vehicle loading up to 9t, for heavier loadings please contact Hydro International

Stormbloc® MX

Full block Length / width / height:  800 / 800 / 660

Half block Length / width / height:  800 / 800 / 360

Constructed full block weight:  18.6 kg

Nominal storage capacity per full block:  0.405 m3

Porosity: 96%

Vertical ultimate compressive strength:  350 kN/m2

Horizontal ultimate compressive strength:  135 kN/m2

Cover level (Traffic loading ≤30 tonnes):  ≥0.8 m - 2.36 m

Maximum installation depth:  3 m

Stormbloc® SX

Full block Length / width / height:  800 / 800 / 660

Half block Length / width / height:  800 / 800 / 360

Constructed full block weight:  18.6 kg

Nominal storage capacity per full block:  0.405 m3

Porosity: 96%

Vertical ultimate compressive strength:  420 kN/m2

Horizontal ultimate compressive strength:  165 kN/m2

Cover level (Traffic loading ≤60 tonnes):  ≥0.8 m 

Maximum installation depth:  4 m

Stormbloc® HX

Full block Length / width / height:  800 / 800 / 660

Half block Length / width / height:  800 / 800 / 360

Constructed full block weight:  18.6 kg

Nominal storage capacity per full block:  0.405 m3

Porosity: 96%

Vertical ultimate compressive strength:  630 kN/m2

Horizontal ultimate compressive strength:  235 kN/m2

Cover level (Traffic loading ≤60 tonnes):  ≥0.8 m 

Maximum installation depth:  6 m**

**For shallower cover depths under heavy loading please contact Hydro International

  • Stormbloc® Extra stack
  • Stormbloc® Extra installation
  • Stormbloc® Extra  installation
  • Stormbloc® Extra stacked crates during installation
  • Stormbloc® stormwater storage & infiltration block
  • Stormbloc HX
  • Stormbloc® two high
  • Row of Stormbloc® with Stormbloc® Extra block for pipe connection in the centre
  • Stormbloc® tank with Stormbloc® Inspect and Stormbloc® Extra row for inspection & maintenance access
  • Stormbloc® blocks stacked to save space in transit and on site
  • Stormbloc HX installation
  • Stormbloc HX with Stormbloc Inspect chamber
Q

What is the difference between Stormbloc LT, MX, SX and HX?

A

Stormbloc® LT, MX, SX and HX are all part of our  range of geocellular storage / infiltration blocks, along with the Stormbloc® Inspect chamber. 

Stormbloc® LT is a lighter, cost-effective option suitable for landscaped or light traffic areas (cars ≤3 tonnes), up to a depth of 3 m.

Stormbloc® MX is a medium-strength option suitable for car parks, bus lanes, pedestrian zones with delivery traffic, access roads to residential complexes and clinics, up to a depth of 3 m. 

Stormbloc® SX is a high-strength option which is ideal for installation beneath heavily loaded and high-traffic areas, such as roads and car parks or for installations up to 4 m in depth.  

Stormbloc® HX is a very high-strength option for installation beneath heavily loaded areas such including access roads in industrial and commercial car parks (cars and lorries), lorry loading bays. Capable of shallower cover depths and extra deep installations up to 6 m.

You can find a like-for-like comparison table in the Stormbloc® Optimum brochure.

Q

How deep can my storage tank be?

A

As a general rule, for a tank constructed with Stormbloc® LT or Stormbloc® MX the total excavation depth should not exceed 3 m.

Because they are of greater strength, Stormbloc® SX has a maximum installation depth of 4 m and Stormbloc® HX of up to 6 m.

Tank designs in excess of these limits can often be achieved with a bespoke design from our design team. For further details, please call 01275 337937 or email stormwater@hydro-int.com

Q

How much water can be stored in a single Stormbloc® element?

A

Stormbloc® LT

Storage volume for a single element (800 mm x 800 mm x 300 mm) is 0.203 m3
Storage volume for the base plate (800 mm x 800 mm x 30 mm) is 0.017 m3

Stormbloc® MX/SX/HX

Storage volume for a full block (800 x 800 x 660 mm) is 0.405 m3
Storage volume for a half block (800 x 800 x 360 mm) is 0.221 m3

Q

What is the minimum cover level for a Stormbloc installation?

A

The minimum cover level is dependent on the loading that the tank will be subject to and which Stormbloc® blocks are used.

Stormbloc® LT
  • Cover level (landscaped area, no traffic):  ≥0.5 m
  • Cover level (light traffic loading ≤ 3 tonnes* ):  ≥0.8 m
Stormbloc® MX
  • Cover level (Traffic loading ≤30 tonnes):  ≥0.8 m - 2.36 m
Stormbloc® SX
  • Cover level (Traffic loading ≤60 tonnes):  ≥0.8 m 
Stormbloc® HX
  • Cover level (Traffic loading ≤60 tonnes):  ≥0.8 m 

For further details download the Stormbloc® Optimum brochure.

If you have any queries regarding cover levels, please contact the Hydro International team at stormwater@hydro-int.com

 

Q

What are the lateral loadings for the Stormbloc® blocks?

A

Stormbloc® LT
  • Vertical ultimate compressive strength:  320 kN/m2
  • Horizontal ultimate compressive strength:  100 kN/m2
Stormbloc® MX

Full block

  • Vertical ultimate compressive strength:  350 kN/m2
  • Horizontal ultimate compressive strength:  135 kN/m2
Stormbloc® SX

Full block

  • Vertical ultimate compressive strength of 420 kN/m²
  • Horizontal ultimate compressive strength of 165 kN/m²
Stormbloc® HX
  • Vertical ultimate compressive strength:  630 kN/m2
  • Horizontal ultimate compressive strength:  235 kN/m2

Q

What maintenance is needed?

A

Access for CCTV inspection, maintenance and cleaning are all possible for Stormbloc® Optimum range.  We would always recommend a scheduled maintenance routine that is completed at least once a year.

Hydro-Logic® Smart Maintenance technology, which allows remote monitoring to provide real-time insight into water levels and also be integrated into the tank. This will send automated alerts when the tank 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.

 

Q

How are the blocks delivered?

A

Stormbloc® LT

Stormbloc® LT elements are delivered stacked in compact nests on jumbo pallets with maximum dimensions of 1.6 m length x 0.8 m width and 1.5 m height.  Each pallet can hold a maximum of 26 Stormbloc® elements or 92 base plates.

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Stormbloc® elements and base plates stacked on jumbo pallets

Stormbloc® MX/SX/HX

The Stormbloc® MX/SX/HX blocks are delivered stacked into compact nests on jumbo pallets with maximum dimensions of 1.6 m length x 0.8 m width x 1.5 m height.  
Each pallet can hold max. 34 x Stormbloc® MX/SX/HX Extra Elements. 

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Stormbloc® Extra blocks stacked on a jumbo pallet

 

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