The requirements for the elements of the tank apply to the material forming the bottom, various reinforcements and seabed seals, the method of strengthening the banks of the reservoir and the method and quality of the installation of water supply and drainage.
The basic requirement for the bottom of the tank is tightness, that is, the highest possible impermeability to water and the durability of the bottom surface and the applied seal. In natural reservoirs, the bottom formed by clay or clay materials tends to slide downwards, and in tanks with continuous flow of water or periodically emptied tanks, the bottom material is often washed and dripped off. Therefore, the bottom of natural reservoirs should be strengthened by covering with a layer of coarse aggregate, paving, etc.. Artificial tanks built on permeable soils should have bottoms made of materials ensuring the best possible tightness and durability. Bottom hydration and sealing should be designed taking into account the pressures caused by water load and the effects of low temperatures after emptying the tank or its freezing when filled with water..
If the tanks are built on insufficiently stabilized soil, where subsidence is expected, the coating forming the seal should be sufficiently flexible, that it does not crack or tear as a result of movements caused by subsidence, which would lead to a rapid loss of water. Seepage water can not only lead to faster settling of the granite, but even to rinse it out. In such cases, the tank may be completely destroyed.
The quality of the material forming the bottom of the tank should make it easier to keep it clean and allow easy cleaning of the bottom after draining the water. The bottom of the reservoir can be decorative, obtained by lining it with materials such as glazed ceramic tiles, various colored concrete slabs etc..