Monolithic constant walls thickness “CLY” PE above ground tank for non particularly aggressive fluids storage. Equipped with an adequit number of female threaded holes with brass inserts for eventual insertion of loading/unloading nozzles. An access with a bolt hole of 400mm in diameter is located on the upper generatrix of the basin with a female bayonet locking cap and a vent. The tank is suited for drinking water storage and other reactants according to the polyethylene compatibility charts.