Reservoir No. 4, located a half mile southeast of the filtration plant along Monroe Street, has a capacity of 150 million gallons and was constructed in 1919. Reservoir No. 4 receives its water from No. 5 from the Miller Ditch and from the Berry Ditch. The flow from the pool in the Miller Ditch receives the water from all three sources, where pumps discharge the water into Reservoir No. 4. Water flows by gravity from No. 4 into Nos. 1, 2, or 3 Reservoirs.