What is Drainmax ?

The BMS Drainmax is a high-quality tunnel type storm water attenuation and infiltration system. It is lightweight and extremely easy/quick to install with maintenance free systems available. The semi-circular tunnels have a 100% buffering capacity and three times the storage volume of a conventional gravel ditch. Drainmax Tunnels are certified by the German DIBT (Structural Engineering Institute). DIBT Certification is the German equivalent of full Agrément Certification.

How Does it Work?

The Drainmax forms an artificial underground reservoir where surface/storm water can be stored and then released at a sustainable rate preventing flooding at the installation location and downstream in water courses and municipal sewers.

What Makes the Drainmax Unique?

The Drainmax Tunnel system offers a winning combination of value, quality and ease of installation/maintenance.  Drainmax systems allow a large amount of stone to be used in conjunction with the system, which contributes to the volume capacity providing excellent value.  It is a high quality system that is manufactured in Germany to ISO 9001:2015 Quality.  The tunnels are lightweight and can easily be lifted by two people.  Installation is as simple as overlapping the tunnels.

You can view a video on the Drainmax below.


The Drainmax is manufactured from only certified reprocessed High Density Polyethylene (HDPE) and is moulded in Germany under an ISO 9001 Quality Management System.

The Drainmax is fully German DIBT (Structural Engineering Institute) certified.  DIBT Certification is the German equivalent of full Agrément Certification.

DIBT certification is a designated certification route for building materials not subject to a specific European Directive.  Certification provides validation on technical performance and load bearing and is available from BMS.

How to Install Drainmax Tunnels

The Drainmax is one to the easiest systems on the market to install.  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 and up 450 mm.  40 mm clean stone is placed under, between and above the tunnels.  This stone contributes to the storage volume.  Each start section is equipped with a single DN100 (4″) hole as an inlet and is capable of connecting to pipes with a diameter of up to DN300 (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.

Drainmax is a great value choice especially when a large area is available for attenuation, infiltration or as a soakaway.  It can be installed as a fully sealed impermeable attenuation system e.g. 0.75 mm HDPE geomembrane surround/clay liner or as a permeable infiltration system e.g. non-woven geotextile 300 g/m2.  BMS can advise on this and look after the whole process from design to installation/certification.

Large Drainmax Installation in Housing Estate

Maintenance of Drainmax Tunnels

The biggest concern of many planning authorities is the level of maintenance that they will have to do after installation especially if they are taking it in charge after installation.  BMS R&D Department innovated a new installation method to make Drainmax installations essentially maintenance free:

  1. Each Drainmax installation has at least one ‘isolator row’.  This row is covered with a permeable geotextile with a MacTex impermeable base (as below).
  2. The full flow of the installation is routed into the isolator row(s).  Each Drainmax tunnel provides 52 No. 26 mm diameter slotted openings, strategically placed to allow the incoming flow to permeate evenly and speedily.
  3. This unique feature prevents surcharging and eliminates the need for an upstream manifold and complicated downstream distribution pipework arrangements.
  4. All grit and silt is contained within the isolator row, which can be jet washed if required.
  5. The Grit/Silt is then washed through to the outlet manhole, so all maintenance takes place at the inlet/outlet manholes.
  6.  If combined with a BMS Petrol Interceptor and BMS Stormbreaker Defender Vortex Silt/Oil/Debris Separator virtually all grit/silt is removed before discharge.

Poster showing an isolator row and maintenace of Drainmax Tunnels.

Poster showing an isolator row and maintenace of Drainmax Tunnels

Technical Details

Drainmax-T-1600/60 Middle tunnel

Size (L x H x B) 2340 x 781 x 1375 mm
Effective length 2250 mm
Weight 32 kg
Volume (net) 1600 litre
Load Class HGV60

Drainmax-T-100-S/60 Start Module

Size (L x H x B) 443 x 767 x 1375 mm
Weight 5.5 kg
Inlet DN 100 standard at the top
Inlet DN 150-300 imprinting 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
Weight 5.5 kg
Inlet DN 100 standard at the top
Inlet DN 150-300 imprinting at the top and bottom
Volume (net) 100 litre

Load Tolerance Capacities of Drainmax 60 

Installation Surface Type Max Axle Load Minimum/Maximum Cover
Accessible Gravel Surface N/A 0.501 – 3.00 m
12 t Lorry (Alternative Surface Load = 6.7 kN/m2)

Gravel Surface

8.0 t 0.501&2 – 2.75 m
Heavy Goods Vehicle 30 (Alternative Surface Load = 16.7 kN/m2)

Paved Surface

13.0 t 1.00 – 2.00 m
Heavy Goods Vehicle 60 (Alternative Surface Load = 33.4 kN/m2)

Paved Surface

20.0 t 1.00 – 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.

Track Record/Previous Installations

More than 100,000 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.

Surface Water Design and One Stop Shop

BMS have over 30 years’ experience in sewage, wastewater and surface water design

BMS can design your surface water management system and have invested in specialist software to provide cutting edge project design.  

Design Services offered by the BMS

  • BMS can design your full surface water management or SuDS system from first principles.
  • BMS have invested in specialist software, which produces comprehensive design data.  The design will include a full proposal, drawings and design calculations.
  • BMS can offer advise on sizing/selecting the correct attenuation/infiltration system, petrol/oil interceptor (separator)vortex silt/oil/debris defenderoutlet flow controls & storage tanks.
  • BMS uniquely offer a ‘one stop shop’ from design to installation for our surface water management products.
  • All products are ISO 9001:2015 Quality manufactured in Ireland and Europe.
  • BMS offer free Continuing Professional Development (CPD) Seminars on Surface Water Management and Sewage Treatment at your premises.
  • BMS can design a custom pump station solution for your requirements in GRP/FRP.  This can include emergency storage and valve chambers.  BMS Pump Stations are normally delivered ‘ready to go’.
  • BMS can design a vehicle wash water recycling system for you with 100% Recycle and Zero Discharge.

Product Highlights

  • Excellent value-for-money

  • Full Performance & Backup Data

  • Lightweight & Easy to Install

  • 100% Buffering Capacity

  • Up to 10 Tonne Axial Loading

  • Maintenance Free Installation

  • Full DIBT Certification

  • Permeable/Impermeable Installation

  • Transports in Minimal Space

  • ISO 9001:2015 Quality

  • Full Irish/EU Design & Manufacture

  • Full Design Support from BMS

Product Awards

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