A field study on overnight stagnation of drinking water in domestic distribution system

Abstract

The present study investigates the influence of in­house installation systems to the tap water quality. In the study were collected more than 100 tap water samples from one important city situated in South­East part of Romania with approximately 250,000 inhabitants in order to get an overview of the current contamination level of drinking water (chemical and microbiological) at the consumer’s tap. The quality of drinking water provided by the Water Company was situated in the limits imposed by the National Legislation. The metal concentrations recorded in tap water samples collected with tap flushing procedure were situated under the maximum admissible values, in all cases. The data obtained for 41% of first draw samples (samples collected first in the morning from kitchen without previous flush of the tap) indicated a pollution of drinking water with some metals (Cu, Fe, Ni and Pb) as result of domestic equipment types (pipe, tap, fitting). High concentrations of Cu, Fe and Pb were recorded in households where most of the material used in domestic distribution system was either copper, either cast iron or lead. The study results indicate that in summer period, under the influence of high temperature, the mesophilic bacteria could exceed the admissible values. Biological results showed that in about 55% of the first draw samples, the number of bacteria (at 22˚C and 37˚C) exceeded the admissible limits, but flushing the tap for more than five minutes lead to improve water quality. Only 14% of the samples remain non­compliance samples. The conclusion of the study indicates that materials used and stagnation of the water in domestic distribution systems affect the drinking water quality at the consumer’s tap.