This article deals with the issue of the amount of clay type nano-fillers used for the improvement of mechanical properties of the basic material HDPE. These fillers already showed their positive influence on various mechanical properties. This article is primarily concentrated on the percentage of filling, which has a significant influence on these properties and also on the final product price in which is the price of used fillers included. It is desirable to find a suitable concentration of filling of the basic material for the improvement of creep properties. As a percentage of filling the lower concentrations were used which are in the practice more common in connection with the nano-fillers which have a high ratio of shape dimensions.