Domestic hot water consumption has been measured in 12 apartment buildings of different sizes (11 to 378 apartments) in Belgium. Each building was monitored for a period of 1 or 2 months with a measurement interval of 1 second. Peak flow rates were deduced from these data for each building. The measured peak flow rates were converted to reference conditions in order to obtain flow rates which can be compared and be used for dimensioning purposes. In this article, a new conversion method is suggested and the different steps are discussed. These standardised peak flow rates are then compared to the peak flows as calculated in accordance with existing guidelines in order to determine the relevance of these guidelines for Belgium. DIN 1988-300:2012  was found to be most appropriate.