Measurement caliber for drainage pipes and rainwater-inlet connectors: computed by design centerline length (to centers, no deduction of auxiliary structures), contrasted with "manhole-deducting" local calibers and with workmanship provisions

Topic Positioning

Clarifying the start/stop caliber for measuring municipal drainage pipes and inlet connectors: measure to the center of inlets/manholes or to the inner face (edge), and distinguishing "centerline (no deduction)" from local "manhole deduction" calibers. For municipal network projects under the current national standard or Beijing's consumption standard.

Core Conclusions

1. Beijing DB11/T 2382-2024 Clause 7.4.26 (drainage pipe laying): "Quantities are computed by design centerline length, without deducting the lengths occupied by auxiliary structures" (the clause also notes: consumptions preferably include water-tightness testing; pipes in sleeves: labor x 1.10).
2. Clause 7.4.31: "Rainwater-inlet connectors follow Clause 7.2.15" — i.e., the road-works rule "connector laying quantities are computed by design centerline length". Network and road provisions agree: centerline, no deduction.
3. Clause 7.4.32: "Standard manholes are counted by design quantity per unit" — manholes by unit, pipes by centerline, each its own; pipe lengths are not reduced by manholes or inlets.
4. National GB/T 50857-2024 Appendix E: Table E.1.1 "pipe laying" (040501) by design centerline length, without deducting auxiliary structures, fittings, or valves; unit m; Clause E.5.6: "rainwater-inlet connectors are listed per the pipe-laying items of Appendix E.1" — connectors are not merged into the inlet but listed separately in m.
5. The "manhole-deducting" caliber is not "measure to the inner face" either: Shenzhen SJG 181.4-2024 Vol. 4, Clause 1.2.3: "Drainage pipe laying quantities are computed in meters as the center-to-center length minus manhole lengths; per-manhole deductions per Table 1.2.3" — datum center-to-center, deductions tabulated, not actual inner-face measurement.
6. Workmanship != measurement: DB11/T 1493-2017 Clause 6.1.3, "one connector end flush with the inlet inner wall, the other protruding not more than 20 mm inside the manhole", is an installation requirement, not a takeoff basis for "measure to face/edge".

One-line conclusion: under the national or Beijing caliber, drainage pipes and connectors are measured to centers (design centerline), no deduction for inlets/manholes; "measure to edge then deduct" is no current caliber's method.

Applicable Boundaries

• First confirm the applied standard/volume: under GB/T 50857-2024 or DB11/T 2382-2024, centerline without deduction; under manhole-deducting local quotas (e.g., SJG 181.4-2024), "center-to-center minus tabulated deduction". The two must not be mixed.
• This card targets pipe (including connector) length measurement; manholes and inlets are counted by unit/set separately — no conflict.
• Connectors measured to centerline do not deduct end inlets/manholes; water-tightness testing is in the laying consumptions, not counted again (Beijing).
• Installation practices and tolerances in acceptance codes are not measurement rules; older or other provinces' volumes follow their own chapter notes.

Further Reading

• DB11/T 2382-2024 Clauses 7.2.15 (road: connector laying), 7.4.26, 7.4.31, 7.4.32 (network: laying and auxiliary structures).
• GB/T 50857-2024 Appendix E, Table E.1.1 (040501), Clause E.5.6.
• SJG 181.4-2024 Vol. 4, Clause 1.2.3 and Table 1.2.3 — the out-of-town "manhole deduction" comparison.
• DB11/T 1493-2017 Technical Specification for Urban Road Rainwater Inlets, Clause 6.1.3.
• Practice: takeoff uses design centerline between inlet/manhole centers; connectors listed separately in m; inlets/manholes by unit — avoid mixing "manholes by unit" with "pipes measured to edge".