182. Valium can stay in your system and be detected in urine for up to 5-7 days after therapeutic use. Chronic use (over one year) of Valium, however, can be detected much longer. The detection window for Valium in urine screens is up to 4-6 weeks.More here on the detection window and drug testing for Valium.We invite your questions about Valium drug screens at the end.alium half life: how long does Valium stay in your system. The half life of any drug, medication or substance is the period of time necessary for 1/2 the drug to be eliminated or disintegrated by natural processes in the body. The half life of Valium is particularly long, 20-80 hours.