Quantity calculation and consumption-standard sub-item application for grooved-connection fittings of sprinkler pipes (mechanical tees, grooved fittings, couplings/clamps) - mainly Beijing DB11/T 2382-2024

Topic Positioning

For sprinkler (automatic water-extinguishing) systems using grooved-connection workmanship: the quantity-calculation basis and consumption-standard sub-item application for mechanical tees, mechanical crosses, finished grooved fittings (clamped elbows/tees/crosses) and couplings (grooved connectors). The primary basis is Chapter 6.9 of the Beijing "Construction Consumption Standard" DB11/T 2382-2024 (general installation works - fire-protection works - water-extinguishing systems), cross-checked against GB/T 50856-2024 and GB 50261-2017 for the measurement and construction-compliance bases.

Core Conclusions

1. Pipe length (take-off basis): Clause 6.9.13 - "Pipe installation quantities shall be calculated by the centre-line length of the pipes shown on the design, without deducting the lengths occupied by valves, fittings and various components." GB/T 50856-2024, Table J.1.1, note 1, same basis: "In the quantity calculation of water-sprinkler steel pipes and fire-hydrant steel pipes, the lengths occupied by valves, fittings and various components are not deducted." The lengths of mechanical tees, couplings and grooved fittings are never deducted.
2. Mechanical tees / mechanical crosses (hole-cut type): measured per "set" by the design quantities, with a separate installation sub-item. Clause 6.9.16 - "The construction consumptions of steel pipe (grooved connection) shall include the work content of grooved-coupling (straight coupling) installation; grooved fittings such as elbows, tees and crosses shall have separate fitting-installation items set by size; fitting-installation quantities shall be calculated by the design quantities, and each set of grooved fittings shall include the clamp and the gasket." The Beijing standard sets "steel pipe (grooved connection) hole-cut fittings" sub-items (work content includes hole cutting, checking the concentricity of the gasket and hole, and tightening the clamp parts), e.g. DN100 -> C9-1-25 (labor 0.1470 work-days/set, grooved mechanical connector 1.0050 set/set, hole-cutting machine 0.0209 shifts/set), DN300 -> C9-1-30 (labor 0.3410 work-days/set, hole-cutting machine 0.0437 shifts/set).
3. Finished grooved fittings (clamped elbows, tees, crosses): likewise listed separately per "set" by the design quantities, under the "steel pipe (grooved connection) grooved fittings" sub-items (work content includes pipe cutting, groove rolling, aligning and installing the clamp parts), e.g. DN100 -> C9-1-35 (labor 0.1600 work-days/set, grooved connector 1.0050 set/set), DN300 -> C9-1-40 (labor 0.3840 work-days/set). Distinction: hole-cut mechanical tees/crosses go to the "hole-cut fittings" sub-items, finished clamped fittings go to the "grooved fittings" sub-items - both measured per set, but the workmanship and sub-items differ.
4. Couplings (grooved connectors) are not itemized separately: (1) butt joints of straight pipes are already included in the pipe installation sub-items - e.g. DN300 pipe sub-item C9-1-20: steel pipe 1.0200 m/m, grooved coupling (with rubber ring) 0.1667 set/m (about 1 per 6 m of straight pipe), work content includes pipe cutting, groove rolling, clamp installation, hydrostatic test and water flushing; (2) at fittings they are included in the fitting sub-items (1.0050 set/set). When compiling a budget, count only the number of fittings, not the number of couplings; only for owner-supplied-material reconciliation and procurement is the quantity estimated separately as "about 1 coupling per 6 m of straight pipe + couplings accompanying fittings".
5. Different rules for threaded connection (common for sprinkler DN < 100): Clause 6.9.14 - "The construction consumptions of galvanized steel pipe (threaded connection) shall include the work content of fitting installation; fitting material quantities may be calculated by the design quantities or executed per Table 6.9.14." Table 6.9.14 reference fitting quantities (pieces/m), e.g. DN50: cross 0.120, tee 0.250, elbow 0.010, coupling 0.125, reducing coupling 0.303, total 0.808; threaded fittings have no separate installation sub-item.
6. Design and construction cross-check (GB 50261-2017 Clause 5.1.11): item 6 - "the connection of distribution mains (risers) with distribution pipes (horizontal pipes) shall use grooved fittings and shall not use mechanical tees"; item 5 - the hole spacing of mechanical tees shall not be less than 500 mm and of mechanical crosses not less than 1000 mm, and the branch-pipe diameter shall satisfy Table 5.1.11; grooves and holes shall be made with dedicated groove-rolling and hole-cutting machines and treated for corrosion protection (inspection: 20% sampled, not fewer than 5 places). Where the drawings use mechanical tees at such positions, or the hole spacing/branch diameter does not satisfy the provisions, raise a design clarification first - do not measure directly off the drawings.

Applicable Boundaries

• Measurement premise: fitting quantities are calculated by the design quantities (6.9.16); hole positions and sizes per the design drawings.
• The sub-item numbers and consumption data come from Chapter 6.9 and Appendix C (Tables C.9.1-3.1 to 3.3) of the Beijing local standard DB11/T 2382-2024 and apply only to Beijing-area pricing; other regions must switch to their local consumption standards/quotas - the method may be referenced, the data must not be copied.
• "Couplings not calculated separately" is the itemizing basis for compiling budgets/consumption documents; for material write-off, stocking and owner-supplied-material settlement, coupling quantities must be estimated separately.
• Grooved connection and threaded connection have different rules (6.9.14 vs 6.9.16); where one system mixes both workmanships, apply them separately.
• The GB 50261-2017 provisions are construction/acceptance compliance checkpoints (positions using mechanical tees, hole spacing are design and construction requirements) and do not affect the forward calculation of quantities.

Further Reading

• DB11/T 2382-2024 "Construction Consumption Standard", general installation works, 6.9 fire-protection works (water-extinguishing systems), Clauses 6.9.12-6.9.24; Appendix C: Table C.9.1-3.1 "steel pipe (grooved connection)" (C9-1-20 etc.), continued Table C.9.1-3.2 "steel pipe (grooved connection) hole-cut fittings" (C9-1-25, C9-1-30), continued Table C.9.1-3.3 "steel pipe (grooved connection) grooved fittings" (C9-1-35, C9-1-40); Table 6.9.23 complete-product table (alarm devices, indoor/outdoor fire hydrants, fire-department connections).
• GB/T 50856-2024 "Standard for Calculation of Quantities of General Installation Works", Appendix J fire-protection works, Table J.1.1 water-extinguishing systems (code 030901), explanatory notes.
• GB 50261-2017 "Code for Installation and Acceptance of Sprinkler Systems", Clause 5.1.11 on grooved-fitting connections and its commentary.
• GB 5135.11 "Sprinkler Systems, Part 11: Grooved-fit connectors" (ductile-iron grooved fittings, EPDM gaskets etc.).