The main put-pose of this work was to investigate the influence of the material of the pipe, through which scalant water (4 mM of CaCO3) was magnetically treated, on the calcium carbonate precipitation process. Tested solutions were exposed to a magnetic field (MF) of 0.16T for 15 min with different flow rates (0.54-0.94 L min(-1)) and pH (6-7.5). Magnetic water treatment and pipe material (PTFE, Tygon, PVC, copper, and stainless steel) effects on CaCO3 Crystallization were assessed by means of a precipitation test based on the dissolved-CO2 degasification method. It was shown that magnetic treatment (MT) affects calcium carbonate crystallization by increasing the total precipitate quantity and by favouring its formation in the bulk solution instead of its incrustation on the walls. This was observed for all used pipe materials but, it is strongly dependent on their physico-chemical properties. It was found that the homogeneous and total precipitation ratios were significantly influenced when MF was applied through non-conductive materials. It was also found that for the same pipe material, the surface roughness plays an important role on the effect of MT on CaCO3 crystallization. In addition, it was shown that the pipe material strongly influences the nucleation process of CaCO3 even in the absence of ME (C) 2009 Elsevier B.V. All rights reserved.