Fabric tank


Not everyone has the perfect cellar for storing wood pellets. That’s why ÖkoFEN supplies a range of ready-made Flexilo fabric tanks in a variety of sizes, where wood pellets can be stored in a way that makes the best use of space and protects them from moisture.


A total of 40 sizes are available, with a capacity ranging from 450kg to 12 tonnes. These include the Flexilo Compact, which boasts a much greater capacity than the standard model for the same size.

With a ceiling height of only two metres you can accommodate up to 6.5 tonnes of pellets. An integral auger feeder and and a flexible sloping floor design ensures the tank can be emptied completely.


1. Fabric tank with auger 2. Fabric tank with suction system 3. Size of the fabric tank 4. Location of the fabric tank 5. Fitting up the tank and boiler rooms

Flexilo fabric tank

Flexilo fabric tank

These storage solutions have been specially designed for ÖkoFEN pellet boilers. The tank consists of a polyester fabric interwoven with metal thread.

The high-grade fabric is dust-tight, permeable to air and permanently anti-static. Installed quickly and simply, Flexilo fabric tanks are available in sizes from 450 kg (manual filling) to 12 tonnes with an auger discharge or vacuum suction system.

Special sizes are available on request.

Flexilo compact fabric tank

Flexilo compact fabric tank

The Flexilo Compact fabric tank is an innovative refinement of the original which, with its extension spring system, allows up to 60% more filling volume than the equivalent size of standard tank. Thanks to an integral pellet feeding auger and the elastic sloping floor, the tank is guaranteed to empty completely every time.

There are two versions of the Flexilo Compact, for high and low headroom situations. Even with a ceiling height as low as two metres, larger quantities of pellets can be stored with ease.

The size of the storage room

The size of the storage room

There are some basic requirements for a pellet storage room. It must be at least 8cm wider than the flexi tank itself and 30cm longer than the tank on the side with the filling unit.

A minimum ceiling height of two metres is needed and to be filled to their maximum capacity most flexi tank sizes require a 2.4 metre ceiling height. Your storage room will also need a vent or window which is 170cm².

Outdoor installation

Outdoor installation

An ÖkoFEN flexi tank can even be installed outside of the building containing the boiler.

A simple lean-to arrangement, with a roof and side panelling can protect it from the weather (rain and sun protection is obligatory).


The pellets are transported to the boiler using the efficient vacuum suction system.


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1. Fabric tank with auger


Fabric tank and heating system are located in the same room.

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2. Fabric tank with suction system


Fabric tank and heating system are up to 20m apart.

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3. Size of the fabric tank


The tank size depends on the building heating load. Based on average heating habits, outcomes the following rule of thumb:
1kW heat load = 400kg of wood pellets a year.


For example:
Heating load 12 kW x 400 kg = 4800 kg ....... fabric tank KGT2618
Heating load 10 kW x 400 kg = 4000 kg ....... fabric tank S2622H
Heating load   7 kW x 400 kg = 2800 kg ....... fabric tank S190H


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Flexilo is available in the following sizes


Item no. Length Width Height* Filling capacity**
S110H 1,100 mm 1,100 mm 1,350 mm 450 kg (hand filling)
S160H 1,700 mm 1,700 mm 1,970 mm 2.0 - 2.5 t
S190H 2,040 mm 2,040 mm 1,970 mm 2.8 - 3.2 t
S220H 2,300 mm 2,300 mm 1,970 mm 3.1 - 3.6 t
S260H 2,580 mm 2.580 mm 1,970 mm 4.0 - 4.6 t
S2216H 2,300 mm 1,700 mm 1,970 mm 2,7 - 3,1 t
S2219H 2,300 mm 2,040 mm 1,970 mm 3,0 - 3,4 t
S2619H 2,580 mm 2,040 1,970 mm 3.0 - 3.6 t
S2622H 2,580 mm 2,300 1,970 mm 3.6 - 4.2 t


* Stayer height ** Filling capacity depends on the bulk weight of pellets (kg/m³) as well as the ceiling height

and can differ by up to 20%. For the maximum filling volume, a ceiling height of at least 240 cm must be available.

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Flexilo Compatc is available in the following sizes


Minimum ceiling height 185 cm 

Item no. Length Width Height* Filling capacity** at room height of
185 cm 190 cm 200cm 240 cm
KGT1814 1.840 mm 1.440 mm 1.850-1.970 mm 1,3 - 1,6 t 1,4 - 1,8 t 1,6 - 2,0 t 2,7 - 3,3 t
KGT2614 2.580 mm 1.440 mm 1.850-1.970 mm 2,0 - 2,5 t 2,2 - 2,8 t 2,4 - 3,0 t 4,0 - 4,7 t
KGT2618 2.580 mm 1.840 mm 1.850-1.970 mm 2,4 - 3,0 t 3,0 - 3,7 t 3,2 - 4,0 t 5,0 - 6,2 t
KGT2620 2.580 mm 2.040 mm 1.850-1.970 mm 3,3 - 4,1 t 3,5 - 4,4 t 3,7 - 4,7 t 5,5 - 7,0 t
KGT2626 2.580 mm 2.580 mm 1.850-1.970 mm 4,0 - 5,1 t 4,5 - 5,6 t 4,9 - 6,1 t 7,2 - 8,5 t

 * The height of the stayer can be shortened on site **Filling capacity depends on the bulk weight of pellets (kg-m³) as well as the height and can differ by up to 20%. For the maximum filling volume, a ceiling height of at least 240cm must be available.

Folgende Größen stehen beim FleXILO COMPACT zur Auswahl


Raumhöhe 185 cm bis 240 cm

             Länge Breite Höhe1)  Befüllmenge2) bei Raumhöhe von
mm mm mm 185 cm   190 cm   200 cm   240 cm  
KGT1814 1.840 1.440 1.850 - 1.970 1,3 - 1,6 to 1,4 - 1,8 to 1,6 - 2,0 to 2,7 - 3,3 to
KGT1818 1.840 1.840 1.850 - 1.970 1,7 - 2,0 to 1,9 - 2,3 to 2,0 - 2,5 to 3,4 - 4,0 to
KGT2614 2.580 1.440 1.850 - 1.970 2,0 - 2,5 to 2,2 - 2,8 to 2,4 - 3,0 to 4,0 - 4,7 to
KGT2618 2.580 1.840 1.850 - 1.970 2,4 - 3,0 to 3,0 - 3,7 to 3,2 - 4,0 to 5,0 - 6,2 to
KGT2620 2.580 2.040 1.850 - 1.970 3,3 - 4,1 to 3,5 - 4,4 to 3,7 - 4,7 to 5,5 - 7,0 to
KGT2626 2.580 2.580 1.850 - 1.970 4,0 - 5,1 to 4,5 - 5,6 to 4,9 - 6,1 to 7,2 - 8,5 to

1) Höhe (mm) Steher.
2) Die Befüllmenge ist abhängig vom Schüttgewicht der Pellets (kg/m³) sowie der Raumhöhe und kann bis zo 20% differieren. Für die Maximalfüllmenge muss eine Raumhöhe von mind. 240 cm gegeben sein.

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4. The location of the wood pellets tank room

Pellets are delivered by tanker truck and are blown into the store room or the FlexiTank. The truck's pumping hose is max. 30 m length, so the FlexiTank (or rather the filler coupling) must be no more than 30m from the drive, parking space or road. If possible, the FlexiTank room should border at least one exterior wall, since the filler coupling must be accessible from the outside. Where this is not possible, ventilation and filling pipes must be routed to a filler coupling on the outside of the building. (Attention - in some countries fire regulations must be observed).

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Size of the storage room



The room housing the Flexilo must be at least 7 - 10 cm wider than the tank itself.
For example: The S190 tank has a width of 197 cm, requiring a minimum room dimension of 205 cm on three sides, on the fourth side with the filler nozzle there must be 30cm additional clearance.

For example:

The FleXILO S190 requires a minimum room length of 205 cm + 30 cm = 235 cm on the "filler side".

Room height: The minimum room height is 215 cm.


Electrical requirements

The system is pre-wired ready to plug. In the boiler room a light outlet (230 volts) is required.


External emergency stop switch:

An emergency stop switch must be installed outside the boiler room, near the boiler room door.

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Fitments of the tank and heating room


Perimeter walls: The surrounding walls and the ceiling of the pellet storage room and the boiler room should correspond to fire resistance class F 90.  

DoorsAs with all other heating systems, the boiler room and the storage room doors must be fired proof (at least T 30). They must open outwards and fitted with a seal.

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Tank room floor plan

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Tank room sectional view


Filling system: Where a FleXILO is installed in a room, there must be adequate ventilation (window or similar with a minimum area of 170 cm²) to allow air to escape when the tank is being filled.

Fire protection: Further information on fire regulations is available from your local OkoFEN specialist


The normal humidity of cellar walls is not a problem. However, the FleXILO must not touch wet walls. In the case of an outdoor installation, the FleXILO must be protected against rain and UV radiation. To avoid the pellets swelling,
it is imperative that water does not penetrate the tank.

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