A double-skin tank is a tank in which there is a second skin at least up to the height of the maximum permitted filling level and the interstitial space between the inner and outer skin is suitable as a monitoring space. A leak detection system (vacuum leak detector, pressure leak detector or leak detector using a liquid) connected to the interstitial space serves to detect leaks in the inner or outer skin.

Double-skin tanks made of metal (mainly steel) for stationary storage of liquids hazardous to water are available in various shapes and with various volumes. Common variants for above-ground storage are vertical cylindrical tanks with supporting legs or supporting frames, horizontal cylindrical tanks on saddle supports and, for smaller tanks, cubic tanks with flat walls. For underground installation, mainly horizontal cylindrical tanks are used.

Regulatory framework

DIBt grants national technical approvals (abZ)/general construction technique permits (aBG) for construction products not covered by the harmonised part of DIN EN 12285-2 and the corresponding applications (constructrion techniques) if they deviate significantly from the Administrative Provisions – Technical Building Rules of the federal states (VV TB). Compare the common model: MVV TB.

The national technical approvals/general construction technique permits for these products and construction techniques confirm that both the construction and water law requirements have been met. The products and construction techniques are thus deemed to be suitable in accordance with Section 63 of the Water Resources Act (WHG).