Water distribution valves – isolation strategy:\r Where should sluice (gate) valves be provided in a municipal distribution network to enable sectional isolation and maintenance?

Introduction / Context:
Distribution systems must allow operators to isolate sections for repairs or emergencies while keeping most customers in service. Strategic placement of sluice valves (gate valves) provides this flexibility and limits the number of users affected during outages.

Given Data / Assumptions:

• Network consists of trunk mains, sub mains, and distribution laterals.
• Objective is sectional isolation and operational control.

Concept / Approach:
Valves are placed to bracket sections of main, protect critical junctions, and isolate branches. Spacing depends on street grid, customer density, and criticality. A looped grid requires valves around blocks so that any pipe segment can be isolated with a minimum number of closures.

Step-by-Step Reasoning:
Place valves at intervals along straight runs to limit shutoff extents.Install valves at junctions to control flow paths and enable partial shutdown.Provide valves at branching points so branches can be isolated from mains.Comprehensively, all listed locations are appropriate.

Verification / Alternative check:
Standard design guidance recommends spacing to ensure that no more than a defined number of service connections are out during a single main isolation, confirming the need for valves in all listed positions.

Why Other Options Are Wrong:

• Limiting valves to only one location would compromise isolation flexibility and enlarge outage areas.

Common Pitfalls:

• Skipping valves to save capital cost, which increases outage size and repair time impact.
• Forgetting to consider hydrant and PRV zones when planning closures.

Final Answer:
All of the above