The slug method is usually used for what size mains?

• A. Small diameter mains
• B. Large diameter mains
• C. Transmission mains
• D. Distribution mains

Answer: (B)

The slug method is a quick hydraulic test that perturbs a water main by introducing or removing a slug of water and then watches how the pressure or water level recovers over time. This approach works best on large-diameter mains because the bigger water column gives a more easily detectable and interpretable transient response. The slug creates a measurable head change and a slower, clearer recovery in large pipes, making it easier to estimate hydraulic characteristics from the data. In smaller-diameter lines, the response is often too rapid or too small to measure reliably, so the method is not as practical, whereas very large transmission mains can also complicate interpretation. So this method is typically used for large diameter mains.