Disinfection byproducts (DBPs) in water distribution systems (WDS) are monitored for regulatory compliance, while populations are exposed to DBPs in tap water that may be different due to stagnation of water in plumbing pipes (PP) and heating in hot water tanks (HWT). This study investigated the effects of water stagnation in PP and HWT on exposure and risk of DBPs to humans. Trihalomethanes (THMs) in PP and HWT were observed to be 1.1–2.4 and 1.6–3.0 times, respectively, to THMs in the WDS, while haloacetic acids (HAAs) were 0.9–1.8 and 1.2–1.9 times, respectively, to HAAs in the WDS. The chronic daily intakes of DBPs from PP and HWT were 0.6–1.8 and 0.5–2.3 times the intakes from WDS. The cancer risks from PP and HWT were 1.46 (0.40–4.3) and 1.68 (0.35–5.1) times the cancer risks from WDS. The findings may assist in regulating DBPs exposure concentrations.