The DIBT Certified Drainmax Tunnel System consists of lightweight, plastic, semi-circular shells with the capacity to buffer and infiltrate rainwater from sealed surfaces into the ground.  The semi-circular shells have a 100 % buffering capacity and three times the storage volume of a conventional gravel ditch.

What is Drainmax ?

Drainmax Tunnels are certified by the German DIBT (Structural Engineering Institute)  DIBT Certification is the equivalent of full Agrément Certification.  Rainwater can pass freely through the bottom and infiltrate into the ground through holes in the side of the tunnel.

The 60 tonne version, which BMS uses as standard can cope with a load of up to HGV60 (60 tonnes) and has an axle load limit of 20 tonnes (with the correct level of cover)  The tunnels are extremely durable because they are made from High Density Polyethylene (HDPE) meaning they will last for decades.

Each start section is equipped with a single DN 100 (4″) hole as an inlet and is capable of connecting to pipes with a diameter of up to DN 300 (12″) It is possible to construct a large system at minimal cost because the Drainmax system only consists of three different components: tunnel, start and end sections. Moreover the system is stackable to minimise transport costs.

Technical Details

Drainmax-T-1600/60 Middle tunnel

Size (L x H x B)2340 x 781 x 1375 mm
Effective length2250 mm
Weight32 kg
Volume (net)1600 litre
Load ClassHGV60

Drainmax-T-100-S/60 Start Module

Size (L x H x B)443 x 767 x 1375 mm
Weight5.5 kg
Inlet DN 100standard at the top
Inlet DN 150-300imprinting at the top and bottom
Volume (net)100 litre

Drainmax-T-100-E/60 End Module

Size (L x H x B)444 x 736 x 1475 mm
Weight5.5 kg
Inlet DN 100standard at the top
Inlet DN 150-300imprinting at the top and bottom
Volume (net)100 litre

Load Tolerance Capacities of Drainmax 60 

Installation Surface TypeMax Axle LoadMinimum/Maximum Cover
Accessible Gravel SurfaceN/A0.501 – 3.00 m
12 t Lorry (Alternative Surface Load = 6.7 kN/m2)

Gravel Surface

8.0 t0.501&2 – 2.75 m
Heavy Goods Vehicle 30 (Alternative Surface Load = 16.7 kN/m2)

Paved Surface

13.0 t1.00 – 2.00 m
Heavy Goods Vehicle 60 (Alternative Surface Load = 33.4 kN/m2)

Paved Surface

20.0 t1.00 – 1.65 m
1Only valid if installation is frost proof.
2Minimum cover required to move loads over installation.  Please note that if surface is compressed below the minimum depth of cover, it needs to be repaired before recommencing running loads over the installation area.

Other loadings/loading types are possible on request.  Please contact us.


BMS can provide all accessories required for installation including membranes, terram and top hats.  BMS are a ‘one stop shop’ for all surface water requirements including: interceptors, hyrdrobrakesvortex seperators and holding tanks from design to installation.

Load Capacity

Due to their vaulted geometry the tunnels have an enormous load capacity. The Drainmax version which BMS use, with a suitable amount of cover, can withstand loads up to SLW60.

Important: The load capacity specifications refer to light traffic such as car parks, driveways or terminals. In areas with continous, heavy traffic, such as motorways or roads with alternating loads and velocities custom capacity and dimensions are required.  Please contact us for more information.

Track Record/Previous Installations

More than 50,000 m³ of Drainmax tunnel systems have already been successfully installed in many different countries across Europe and Ireland as part of SuDS (Sustainable urban Drainage Systems)  References are available on request.


Drainmax tunnels can be either stacked on pallets or transported individually, directly to the building site. The tunnels can then be offloaded either manually or with a forklift.

Transport and load sizes

  • pallet (L x B x H) =        2.40 x 1.40 x 2.00 m
  • max. pieces = 25 tunnels plus 10 starts/ends
  • pallet weight = 800 kg
  • infiltration vol. =            40 m³
  • lorry or 45 FT Dry Container
  • max. 9 pallets with 25 tunnels each =             225 tunnels
  • infiltration vol. =            360 m³

System Installation

Drainmax tunnels are installed in rows. One row consists of one start and end section brought to the required length by inserting successive middle tunnels. Tunnels are secured simply by overlapping the first ridge of each tunnel; no additional connections are necessary. Depending on the system design, rows are placed side by side with at least a 45 cm gap between rows.

Product Highlights

  • Excellent value-for-money

  • Minimal transport costs (easy stacking)

  • Increased load capacity of up to SLW60

  • 100% porous – minimal space usage

  • Simple and quick installation by linking tunnels together

  • Extended durability by using highly rugged 100% reprocessed HDPE

  • Extremely lightweight and highly portable.

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