Surface tension is the natural effort of liquids to occupy a minimal surface area. It arises as a consequence of the action of cohesive forces between molecules and liquid. Water has a high surface tension due to strong hydrogen bonds. With the addition of surfactants, the surface tension decreases sharply as the monomers begin to adsorb to the surface. Surface tension can be determined by various methods (direct and indirect, for example tearing off the ring, raising the level in the capillaries, increasing the surface area of the membrane), among which the stalagmometer methods and the method of measuring the weight of the drops are the most common. The stalagmometer method is a simple method based on comparative data measuring the number of drops of liquid of known surface tension and the number of drops of liquid by which we determine the surface tension. Surfactants lower the surface tension and are therefore used in detergent formulations, soaps, emulsions, shampoos and many other products from inustry and household. According to the electric charge of the surface-active ion or molecules in aqueous surfactant solution are grouped into four main groups: anionic, neionic, cationic and amphoteric surfactants. The change in surface tension occurs because one part of the molecule is arranged so that the hydrophilic parts of the molecule face the water, and the hydrophobic parts protrude towards the air. Surfactants are the most important group of detergent ingredient and are present in all types of detergent. In order for detergents to meet such high requirements, they are composed of several types of components, each of which individually or in combination with the others has its own task in washing. The main ingredients of detergent are: surfactants, builders, chemical bleach agents, bleach stabilizers, dirt carriers, enzymes, corrosion inhibitiors, antimicrobial properties, foam regulators, softeners, fragrances, fillers and dyes. Due to the large amounts of detergents that are discharges into the sewer after use, their impact on the enviroment is now a lot more being studied.