The design of a tritium processing loop for KATRIN tritium source and results of test set-up operation are presented. The constant source intensity is supported by high purity (> 95% of tritium) of tritium circulated through the source with 4.110-4 g/s rate. The possibility of source parameters stabilization was verified with test facility "TILO" which was built for this purpose. The long term (30 days) deuterium circulation with flow rate 0.2 Pa m3/s shows that using of standard high accuracy pressure sensors from MKS and NI control electronics allows to stabilize the flow rate in the system with 0.1% accuracy. The reliability of process equipment was tested as well during about 3000 h of TILO operation.