1. Scope
- Class K covers manholes, chambers, access points, and other ancillary structures associated with pipelines.
- It also includes ancillary works such as pipe supports, thrust blocks, anchor blocks, and other minor but essential items not included in Class I (Pipes) or Class J (Fittings & Valves).
👉 In simple terms:
- Class I = Pipes
- Class J = Fittings & Valves
- Class K = Manholes, Chambers, Supports, Ancillaries
2. General Principles
- Unit of measurement:
- Manholes & chambers → Number (No.), each measured individually.
- Pipe supports/blocks → Number (No.) or cubic metre (m³), depending on specification.
- Ancillary items → Number (No.).
- Rates include:
- Excavation, foundation, formwork, reinforcement, concrete, masonry/brickwork, covers, frames, ladders, benching.
- For supports & blocks: excavation, formwork, reinforcement, backfilling.
- Testing, finishing, and making good.
3. Sub-classifications
K1 – Manholes / Chambers
Manholes give access to underground pipework for inspection, cleaning, and maintenance.
Types:
- Inspection chambers (shallow, ≤1.0 m deep).
- Manholes (deep access, >1.0 m depth).
- Valve chambers (sluice valves, butterfly valves, air valves).
- Junction chambers (where multiple pipelines meet).
- Meter chambers (for flow meters, instruments).
Details required in BOQ description:
- Type of chamber (inspection, valve, meter, junction).
- Construction material (brick, RCC, precast concrete).
- Internal size (clear dimensions).
- Depth category (e.g., up to 1.5 m, 1.5–3.0 m, >3.0 m).
- Cover and frame (cast iron, ductile iron, heavy duty/light duty).
- Accessories (steps, ladders, benching, watertightness).
K2 – Pipework Supports and Anchorage
Includes all structural supports that ensure pipe stability:
- Thrust blocks (resist thrust at bends, tees, reducers).
- Anchor blocks (hold pipeline in position).
- Saddles, cradles, concrete supports (for above-ground or culvert pipes).
- Wall brackets, hangers, pipe guides.
Measurement rules:
- Thrust/anchor blocks → m³ of concrete or No. (depending on contract specification).
- Brackets/hangers → No.
K3 – Ancillary Items
Covers miscellaneous works linked to pipe systems:
- Marker posts / indicator posts (for buried valves, hydrants).
- Hydrant chambers (sometimes grouped under K1).
- Air valve housings.
- Access covers and frames.
- Drainage sumps or pits.
- Protective barriers / bollards (to protect chambers from traffic).
4. Measurement Rules
- Manholes/Chambers → Measured by number (No.), classified by type, material, and depth.
- Supports/Blocks → Measured by number (No.) or volume (m³) depending on specification.
- Accessories (steps, ladders, frames, covers) → deemed included unless specified separately.
- Excavation, backfilling, and disposal are included unless BOQ notes otherwise.
5. Examples of BOQ Items (Class K)
- Manhole, 1200 × 1200 mm internal, RCC, depth up to 1.5 m, with heavy duty CI cover and frame – No.
- Inspection chamber, precast concrete, 600 × 600 mm, depth 1.0 m, with medium duty DI cover – No.
- Valve chamber, 1000 × 1000 mm, 1.8 m deep, brick masonry, with ladder and heavy duty CI cover – No.
- Thrust block, M20 concrete, for 300 mm dia bend, as per drawing – m³.
- Anchor block, RCC, for 200 mm dia pipeline, PN16 – No.
- Pipe cradle, precast RCC, for 400 mm dia DI pipe, with bedding concrete – No.
- Wall brackets, fabricated steel, for 150 mm dia pipe, hot-dip galvanized – No.
- Marker post for sluice valve, RCC, 1.5 m above GL, painted and lettered – No.
- Bollard, steel tube filled with concrete, 1.2 m above GL, painted yellow-black, near chamber – No.
✅ In summary:
- Class K is about manholes, chambers, supports, and ancillary works related to pipework.
- It ensures access, safety, and structural stability of the pipeline system.
- Items are measured mainly by number, with concrete supports sometimes in cubic metres.
- Detailed descriptions must state type, size, depth, material, accessories, and purpose.
