Abstract: This invention refers to a mold for use on the bottoms of flower pots, characterized in that the mold has a height of at least 5% of the height of the flower pot and its top side has a surface area, which, when in use, is at least 25% of the cross-sectional surface area of the flower pot at the level of its top side, and it refers to the use of such a mold in a flower pot to prevent accumulations of water and excessive moisture in the root area and to a flower pot in which such a mold is integrated.

Abstract: A hollow tank is formed by placing a hollow glass fiber reinforced inner container within a hollow rigid form comprising pieces assembled around the inner container and spaced from it to leave an air gap between the inner container and the inner wall of the assembled form. A suitable concrete material is introduced into the space between the inner container and the assembled form and is allowed to cure as a jacket of concrete integrally attached to and enclosing the inner container. The inner container may be formed by coating an inflated balloon with a thin layer of polyester resin and thereafter spraying on the glass fiber reinforced material to a thickness of a few mm. The concrete may be a standard flowable concrete or a polyester concrete, which is a resin-bonded gravel mixture. The concrete may be the outer layer formed as a jacket around the glass fiber reinforced inner container, or another glass fiber reinforced layer may be formed on the outer surface of the concrete.