In-vessel plasma facing components in fusion reactors such as ITER and DEMO experience high thermal loads and require active cooling, for which water is one possible coolant. The solution where plasma facing components utilise tungsten blocks as sacrificial armour has a joint internal structure of cooling tubes made from the copper base (~99% Cu) alloy CuCrZr. This paper concerns the testing of CuCrZr tubes with respect to flow-assisted corrosion (FAC) at water velocity in the range 8 – 10 m/s and temperature in the range 150 °C – 250 °C. The FAC rate was evaluated by gravimetry, microscopy, and sampling of the water from the re-circulating test system. When the electrochemical potential of the CuCrZr specimens was kept in the reducing range where Cu is thermodynamically stable as a metal, no FAC could be observed on the specimens. At electrochemical potentials that promotes oxidation of Cu through presence of an oxidizer the FAC rate of a straight CuCrZr tube was estimated to be in the order of 400 μm per full power year.