This paper details the results of a fieldwork research showing the effect of pipe fittings on particle accumulation. The total mass of particles accumulated in either pipe fitting affected sections or straight sections varied from: 0.062 – 5.46 g/m (n=22) and 0.058 to 3.61 g/m (n=22). To quantify the mass of washed out particles the resuspension potential method (RPM) or uni-directional flushing (UDF) program were performed in four different drinking water networks (DWN) with population from <10 000 – 700 000; network length: 20-1374 km; DN 100 – DN 250). The flow and turbidity during flushing was measured with online instruments. There was found relation between concentration of total solids (TS) measured from grab samples and turbidity 1NTU=0.2854 mg/l (n=63). The turbidity potential of accumulated particles for PODDS model was determined J= 1.01-2.54. The results showed that in the pipe fittings has greater amount of dry mass compared with straight sections which can be explained due to inertial effects in pipe fittings. It is therefore suggested that UDF of networks could be foresee in most sensitive areas, depending of complicity of the DWN.