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Fuel oil tank – types, tips for cleaning & disposal

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Vitoset twin wall tank and plastic tank

Topics at a glance

A fuel oil tank is an essential component of an oil heating system. Since this proven and reliable heating technology is still widely used, fuel oil storage is also an important issue for many homeowners. In this section, you will learn more about different types of fuel oil tanks, common sizes, statutory regulations and the requirements for cleaning and disposal of old tanks.

Different types for individual needs

When adding a fuel oil tank to a new oil condensing boiler or replacing an existing fuel oil tank, it is important to find the right model. The individual circumstances matter a lot in this case. Oil tanks currently on the market can be divided into three types: 

  • Modular tanks
  • Underground tanks
  • Site-built tanks

Modular tanks are characterised by comparatively small dimensions. This makes them suitable for properties with limited space and narrow access. For the storage of sufficient quantities of fuel, several tanks can be connected to each other and set up in rows or as a block.

The picture shows a Viessmann Vitoset fuel oil tank as a steel/plastic version.
Viessmann Vitoset fuel oil tank as steel/plastic version

The Viessmann Vitoset accessories for oil heating systems include the Vitoset DWT fully sealed, twin wall steel/plastic tanks and the Vitoset KWT plastic tanks. Both models are available in product-specific sizes and approved for storage of up to 5000 litres of fuel oil in rooms with combustion equipment. Special manufacturing techniques that ensure precise wall thickness and include type testing and approval by independent institutions guarantee the consistently high product quality of Viessmann fuel oil tanks. Production and careful quality controls overseen by independent inspection bodies such as the TÜV ensure maximum operational safety.

If there is not enough space in a residential building, the fuel oil tank can be installed underground. Underground tanks are buried in the garden and are therefore hardly visible. However, this means more effort for the earthworks required. In addition, the safety requirements are particularly high. An underground fuel oil tank must have, among other things, a suitable monitoring device that immediately indicates an oil leak.

As the name suggests, these tanks for fuel oil storage are assembled directly on site. This has the advantage that they can be adapted easily to spatial conditions and narrow access is unproblematic. Steel tanks are welded; plastic tanks laminated. However, the complex assembly is time consuming and somewhat more costly.

The right size depends on various factors

The volume of the fuel oil tank depends on the size and energy performance of the residential building and the heating patterns of the occupants. In principle, fuel oil storage should be possible for one year. In detached houses heated with a Vitoladens 300-C or Vitoladens 300-T, tank sizes of 2500 to 4000 litres are typical. However, the demand can be significantly reduced with good insulation. Viessmann partners are reliable advisors in this matter and will support you with the design of the fuel oil tank, taking into account the spatial conditions and all statutory regulations.

Plan sufficient space for the fuel oil tank

When it comes to tank size, the spatial conditions also play a role. When calculating the space required for a fuel oil tank, the available height of the room is an important dimension. For a fuel oil tank with a capacity of 3000 litres, you should plan about 1.5 square metres of floor space for a height of two metres. If the oil tank can only be 1.5 metres high, about two square metres of space are needed.

Smaller oil tanks are allowed in the same room as the boiler. However, a minimum distance of one metre must be maintained. Alternatively, a protective barrier can be constructed. If the capacity is over 5000 litres, special regulations apply to the fuel oil tank. It must be installed separately from the boiler in another room. This is common, for example, in apartment buildings, or commercial and public buildings, which are heated with boilers such as the Vitoradial 300-T or the Vitorondens 200-T. 

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Regular cleaning for smooth operation

Fuel is stored in the fuel oil tank for quite a long period of time. This sometimes causes deposits to form that can disrupt the operation of the heating system. To prevent this, it is advisable to have the fuel oil tank cleaned at regular intervals. For steel tanks, intervals of between five and ten years are recommended; for plastic tanks, as much as eight to 15 years. Service providers firstly pump out the remaining fuel oil, store it temporarily and clean the inside of the fuel oil tank. The tank is then refilled with the fuel oil.

Correct disposal of old fuel oil tanks

If you decide to buy a new Viessmann fuel oil tank, the old one must be disposed of. It should first be professionally cleaned. A contractor certified in accordance with the German Water Management Act (WHG) must be commissioned for this purpose. Corresponding regulations are laid down in the German "Ordinance on facilities for handling substances that are hazardous to water" (AwSV). Disposal itself is best handled by a suitably qualified company. Important: For a fuel oil tank with a capacity of more than 1000 litres or an underground tank, changes such as dismantling must be reported to the responsible authorities.

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