Sewage tanks

Independent in form and material

KLARO-Technik is largely independent of the geometry and material of the clarifier tanks. The volume can be distributed over individual or several tanks or chambers. These can be round or rectangular. The only decisive factor is that certain minimum volumes and heights are maintained.

We advise independently and project-related about advantages and disadvantages - the customer makes the decision.

Concrete septic tanks

Many plants are still classically constructed in concrete tanks. These are generally available everywhere regionally and are available in different sizes and chamber divisions. KLARO works together with several well-known manufacturers of monolithic tanks.


That speaks for concrete containers:

  • Robust
  • Passable
  • Buoyancy-proof
  • Easily visible and accessible
  • Flexible pipe connections
  • Simple installation of the set-up kit

A distinction is made:


  • Container seamlessly manufactured from one piece
  • Advantage: tightness

Ring construction

  • Rings can be placed on top of each other and glued on site in the excavation pit
  • Advantage: Lower weight of the individual parts

Cast-in-place concrete

  • Container is formed and concreted out on site
  • Usually large rectangular containers
  • KLARO specifies the dimensions of the chambers and partitions as well as the position of the drill holes for such projects; the construction company itself is responsible for wall thickness, reinforcement and statics
  • Advantage: Flexibility

Plastic septic tank

Modern containers made of plastic are not only trendy for rainwater cisterns, but also for sewage treatment technology, and are also playing an increasingly important role in larger sewage treatment plants. Here, KLARO can draw on the large portfolio of high-quality plastic tanks from the GRAF Group.


That speaks for plastic tanks from GRAF:

  • Low weight - easy to transport and install
  • Highest stability through state-of-the-art production
  • 100% waterproof and corrosion resistant
  • Longevity - GRAF gives 30 guarantee!
  • Unique fitting accuracy of pipe connections and shaft construction
  • Covers infinitely adjustable up to ground level
  • Sealed up to the container top edge

For our SBR wastewater treatment plants, these series come into question:


  • Sizes 2.700L – 6.500L
  • With half, whole or without partition
  • Made of PP by injection compression moulding
  • Groundwater stability up to tank centre
  • 2.700L and 3.750L up to tank shoulder
  • Earth cover up to 1.5 m possible
  • Connection options up to DN 150
  • Basically truck-accessible 12 t

Carat XL

  • Sizes 8.500 and 10.000 Liter
  • Made of PE in a rotation process
  • Groundwater stability up to tank centre
  • Earth cover up to 2.0 m possible
  • Connection options up to DN 200
  • Basically truck-accessible 12 t

Carat XXL

  • Sizes 16.000 - 122.000 Liter
  • Made of PE in a rotation process
  • Groundwater stability up to tank centre
  • Earth cover up to 1.5 m possible
  • Connection options up to DN 200
  • Basically truck-accessible 40 t

Carat shaft construction

For all Carat tanks, the same professional shaft construction options are available, consisting of

  • Tank Dome
    Depending on the installation depth, you can choose between Tankdom Mini and Maxi. Both offer several DN100 connection options (e.g. for the empty pipe)
  • Telescopic insert
    A telescopic insert allows the shaft cover to be adapted to the terrain with centimetre precision (it can even be inclined on slopes!)
  • Manhole cover
    A walk-on manhole cover made of plastic is supplied as standard. This is light and lockable. With the grass-green colour, the container access is hardly visible in the garden. Alternatively, there are also grey accessible manhole covers available.


  • Extremely flexible

  • Unique fitting accuracy

  • Tight to the top edge of the terrain thanks to inserted seals

  • Continuously adjustable


  • Sizes 600, 900 and 1,200 litres
  • Made of PE in a rotation process
  • Connection options up to DN 150
  • Inside smooth surface without ribs
  • With pump sump
  • Suitable as inspection shaft, pump shaft, for tertiary cleaning stages with UV or chlorine, etc.


  • Sizes 2.000 and 4.000 litres
  • Made of HD-PE with galvanised pipe bandages
  • Connection options up to DN 100
  • For above ground installation


With our innovative retrofit kits, old existing septic tanks can be upgraded with little effort to modern fully biological small sewage treatment plants, which meet all official requirements. The possibilities here are almost unlimited:  Whether concrete or plastic tanks, single or multi-chamber, single tanks or several, round or rectangular, etc.



  1. Required minimum volumes and water depths must be observed:
    – smallest plant 4 PE
    – Minimum volume 3,5 m³
    from 8 PE onwards 650L/EW can be expected
    – Minimum water depth 1,2 m
  2. All chambers must be accessible
  3. The building fabric of the old septic tank must be intact; it must be durable, stable and watertight. This must be seriously examined by an expert!

The preparatory work on the septic tank is very important for the long-term and safe operation of the plant. Our detailed installation instructions for the retrofit kit describe the specified test requirements for the suitability of the tank as well as the measures for preparation before installation of the retrofit kit. Testing, preparation and installation must be carried out and documented by a specialised company.


Most pits are three-chamber concrete pits according to DIN 4261-1 with one half and two quarter chambers. The inlet is usually located in the large half chamber and the outlet in the last quarter chamber. Advantage for KLARO retrofits: The flow direction does not need to be changed - the set-up set is adapted to the chamber division.

Retrofit kits are available for both treatment systems KLARO and KLARO One.

As a rule, the retrofit kit can be placed on the partition wall. There, all parts are easily visible and accessible for inspections.

Learn more about retrofit kits

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