About the optimization in calculations of internal cold and hot water supply systems

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In Ukraine, two methods are used to calculate building utilities: the standard one (DBN 2013) and the "optimal diameter" method. In the EU, there is a standard with a simplified method for calculating building utilities. It also states: "National regulations may require a lower flow rate to avoid water hammer and noise." A small number of European countries have their own national calculation methods, but the standard states that national methods "may be used as an alternative to the European standard in cases where there are reasons for differentiated selection of pipe sizes, e.g. for large buildings, industrial and commercial enterprises, etc.". It is hard to imagine a European country that does not have, for example, "large buildings" and Ukraine is no exception. The "optimal diameter" calculation methodology determines the optimal average speed of water movement in the system, taking into account two criteria: the quality and quantity of water supplied to the consumer. The obtained average velocities are always in the range of "quiet pipes", i.e. less than 1 m/s. Since a simple algorithm exists to solve the problem of finding the best diameters in individual sections, the result is not affected by the designer's experience. As an example, four comparative calculations were performed for an eleven-story building with a total of 192 sanitary facilities and a design section length of 50.5 m. The calculations were performed by two methods for networks made of steel and polyethylene pipes and. It was found that networks calculated according to the DBN method require more electricity for both steel and polyethylene pipes (from 10 to 30% in the hour of maximum consumption). That is why, the use of an alternative methodology for calculating internal networks developed at the Department of Water Supply and Wastewater Treatment of KNUBA not only meets European standards, but also allows to choose more energy-efficient pipe diameters in comparison with those that can be obtained using the DBN.