Water tanks, stone and water-stone are a group of containers independent of the building structure. These trays, with high volume and weight, are usually located in the basement. Warm air circulation, which on sunny days "recharges", and on cloudy days and at night it "discharges" the heat store, is most often forced, hence they also belong to semi-active systems (Hybrid).

The water tank consists of dozens of small plastic containers, glass or aluminium, which are placed on racks or in the empty airspace of ceiling canals, enabling air circulation. Air in passive and semiactive systems is an intermediary medium in the collection and distribution of heat.

A more common solution used for a long time and still very popular are stone and water-stone containers. Admittedly, the volume of the stone storage for storing the same amount of heat as in the water warehouse is two and a half times larger, however, this is due to cheapness, availability, longevity and trouble-free operation, warehouses of this type are still popular.

The size of the stone deposit depends on the surface of the collectors and the amount of thermal energy we want to accumulate, however, the accumulation of heat for the entire heating season in the form of explicit heat for one house is economically unprofitable, if only because of the size of the tray. Accepted, that on 1 m2 of surface receiving solar radiation can be stored in storage 25 into 180 kg of stones. Equally important is the size of the stones, which is related to the height of the deposit (Storage). The rule applies, that the higher the warehouse, the larger the diameter of the stones (for height ok. 1 m should be stones with a diameter from 2,5 into 5 Cm. for height ok. 2,5 m — stones with a diameter of mines. 5 Cm, for height ok. 3,5 m — stones with a diameter from 5 into 10 Cm). Other American experiences have shown, that warehouses as high as 3,5 m. A low bed filled with small stones has less free space between the stones and a larger amount of the total outer surface of the stones, which is in contact with the circulating air (30 dm3 stones with a diameter 2,5 cm has a total external surface approx. 3,6 m2, and the same volume of stones with a diameter 7,5 cm has half the area). Air circulation from the collectors to the warehouse only in exceptional cases is carried out on the principle of free convective movements (the collector must be below the warehouse), it is usually supported by a system of fans – these are semi-active solutions. Stone warehouses are solved on the principle of deposits in a well-insulated bunker in the basement, or in brick or metal containers in the residential part of the house. That's why, to recover some of the heat dissipated from the kitchen or fireplace, ventilation and smoke ducts are run through stone deposits, if possible.
An effective combination, used to store heat obtained from solar radiation, is placed in a stone tank with domestic hot water. Most often it is a non-insulated tank with a capacity of 200 – 400 l. Heat losses from the tank are taken over by air and stone deposits.