Domestic drinking water supply systems (DDWSs) are the final step in the delivery of drinking water to consumers. Temperature is one of the rate-controlling parameters for many chemical and microbiological processes and is, therefore, considered as a surrogate parameter for water quality processes. In this study, a mathematical model is presented that predicts temperature dynamics of the drinking water in DDWSs. A full-scale DDWS resembling a conventional system was built and run according to one year of stochastic demands with a time step of 10 s. The drinking water temperature was measured at each point-of-use in the systems and the data-set was used for model validation. The temperature model adequately reproduced the temperature profiles, both in cold and hot water lines, in the full-scale DDWS. The model showed that inlet water temperature and ambient temperature have a large effect on the water temperature in the DDWSs. ... Read more

The drinking water quality changes during the transport through distribution systems. Domestic drinking water systems (DDWSs), which include the plumbing between the water meter and consumer's taps, are the most critical points in which water quality may be affected. In distribution networks, the drinking water temperature and water residence time are regarded as indicators of the drinking water quality. This paper describes an experimental research on the influence of stagnation time and temperature change on drinking water quality in a full-scale DDWS. Two sets of stagnation experiments, during winter and summer months, with various stagnation intervals (up to 168 h of stagnation) were carried out. Water and biofilms were sampled at two different taps, a kitchen and a shower tap. Results from this study indicate that temperature and water stagnation affect both chemical and microbial quality in DDWSs, whereas microbial parameters in stagnant water appear to be driven by the temperature of fresh water. Biofilm formed in the shower pipe contained more total and intact cells than the kitchen pipe biofilm. Alphaproteobacteria were found to dominate in the shower biofilm (78% of all Proteobacteria), while in the kitchen tap biofilm Alphaproteobacteria, Betaproteobacteria and Gammaproteobacteria were evenly distributed. ... Read more

A PVC 250 mm drinking water pipe that supplies water to ca. 1250 customers has been permanently monitored for almost 10 months. The gathered data covers strain registered on pipes and joints, temperature registered next to these appurtenances and strain registered on coupons of PVC isolated and installed also next to the pipe. The data show an expected positive correlation between temperature and strain on PVC. It also shows that such setup is able to detected daily water pattern use and episodes of water-hammer (due to valve use). Until the coldest weeks of the monitored period the pipe was found to contract more than 5 mm. ... Read more

In the context of the present work it is hypothesized that the condition of a PVC push-fit joint can be obtained from the analysis of the joint's gap width. A perfectly jointed and aligned pipe, for example, should have a constant gap for the complete pipe diameter while a bent joint should show variations of the gap width with the diameter. Therefore, laboratory tests were performed to test the applicability of ultrasound in the assessment of PVC push-fit joints which are ubiquitously used in the Netherlands. In those tests the potential of ultrasound to detect changes in geometrical alignment of PVC pipes was evaluated using a specially built metallic loading frame. This frame supported two 2-meters ø315 mm PVC pipes connected with a push-fit joint. This pipe could be kept in horizontal position or be bent up to an angle ofca. 5 degrees in 11 uniform steps. Results show that when two pipes have a perfect alignment (zero degrees angle between the pipes) the tested ultrasound tool describes quite adequately the real situation and gives good information about the joint's real condition. However, when an angle is imposed on a PVC joint the ultrasound results are not consistent with reality. This discrepancy is probably due to both longitudinal and shear ultrasound waves echoing back to the transducer from the PVC wall. The creation of both longitudinal and shear waves occurs when an angle between the ultrasound transducer and the object being studied exists. This factor is known to complicate the resulting ultrasound scans and the interpretation of the results. In conclusion, for this application ultrasound inspection is vulnerable to changes in geometrical alignment of assessed pipes. Even being unanimously considered as a potential technique for the inspection of polymeric pipes, ultrasound tool is not capable of giving results that permit accurate detection of all known failure mechanism of joints. ... Read more