PLUMBING DESIGN REPORT
Project No: PDR-2025-001
PLUMBING DESIGN REPORT
Mixed-Use Commercial and Residential Development
| Project Name | Riverfront Mixed-Use Tower |
| Project No. | PDR-2025-001 |
| Location | 123 Riverfront Avenue, Dhaka, Bangladesh |
| Client | Riverfront Properties Ltd. |
| Prepared By | M. Ahmed, PE | Civil & Environmental Engineer |
| Date | March 2025 |
| Revision | Rev. 0 – For Construction |
| Standards | BNBC 2020 / IPC 2021 / ASHRAE |
CONFIDENTIAL – FOR CONSTRUCTION USE ONLY
1. Executive Summary
This Plumbing Design Report has been prepared for the Riverfront Mixed-Use Tower, a 24-story development comprising commercial retail spaces on the ground and mezzanine floors and residential apartments on floors 3 through 24. The report presents the engineering basis, system design criteria, and technical specifications for all plumbing systems within the building.
The plumbing design encompasses potable cold and hot water supply, sanitary drainage, storm drainage, natural gas distribution, fire suppression interface, and specialty systems including a rainwater harvesting installation. All systems have been designed in compliance with the Bangladesh National Building Code (BNBC 2020), the International Plumbing Code (IPC 2021), and applicable ASHRAE standards.
| System | Peak Demand | Key Standard |
| Cold Water Supply | 42 L/s (666 gpm) | IPC 2021 / BNBC 2020 |
| Hot Water Supply | 18 L/s (285 gpm) | ASHRAE 90.1 |
| Sanitary Drainage | DN 150 main stack | IPC 2021 |
| Storm Drainage | 120 L/s design flow | BNBC 2020 |
| Natural Gas | 250 kPa supply pressure | NFPA 54 |
2. Project Description
2.1 Building Overview
The Riverfront Mixed-Use Tower is a 24-story reinforced concrete structure with two basement levels. The building occupies a 2,400 m² footprint and provides approximately 52,000 m² of gross floor area. The lower four floors accommodate retail, restaurant, and commercial office tenants, while floors 5 through 24 contain 240 residential apartment units of varying configurations.
| Floor Level | Use | Area (m²) | Occupancy |
| B2 – B1 | Parking & MEP Plant Rooms | 4,800 | Restricted |
| Ground Floor | Retail & Lobby | 2,200 | A-2 / M |
| Mezzanine | Retail & Food Court | 2,000 | A-2 |
| Floors 2 – 4 | Commercial Office | 6,600 | B |
| Floors 5 – 24 | Residential Apartments (240 units) | 39,000 | R-2 |
| Roof Level | MEP Equipment, Water Tanks | 1,400 | Restricted |
2.2 Applicable Codes and Standards
The plumbing systems have been designed in accordance with the following codes, standards, and references:
• Bangladesh National Building Code (BNBC) 2020
• International Plumbing Code (IPC) 2021
• International Mechanical Code (IMC) 2021
• ASHRAE Standard 90.1-2019: Energy Standard for Buildings
• ASHRAE Standard 55-2020: Thermal Environmental Conditions
• NFPA 54: National Fuel Gas Code
• NFPA 13: Standard for Installation of Sprinkler Systems (fire interface)
• WHO Guidelines for Drinking-Water Quality, 4th Edition
• Manufacturer specifications and installation guidelines
3. Water Supply System
3.1 Demand Calculations
Domestic water demand has been calculated using the fixture unit method per IPC 2021 Table 603.1, cross-referenced with BNBC 2020 occupancy-based consumption rates. Demands are tabulated below for each occupancy zone.
| Occupancy Zone | Fixture Units | Peak Demand (L/s) | Daily Usage (m³/day) |
| Residential (240 units) | 1,840 FU | 28.5 | 312 |
| Commercial Office | 420 FU | 6.8 | 74 |
| Retail / Food Court | 380 FU | 5.2 | 56 |
| Common Areas & BOH | 120 FU | 1.5 | 16 |
| Total Building | 2,760 FU | 42.0 | 458 |
3.2 Water Storage and Pressurization
The building utilizes a break-tank and booster pump strategy to ensure code-compliant pressures throughout all floors. Underground cisterns in Basement Level 2 provide emergency storage, while rooftop gravity tanks serve upper residential floors.
| Component | Capacity / Rating | Location | Quantity |
| Underground Break Tank | 200 m³ | B2 Plant Room | 2 |
| Rooftop Gravity Tank | 80 m³ | Roof Level | 2 |
| Booster Pump Set (Low Zone) | 42 L/s @ 45 m head | B1 Plant Room | 1 (1 standby) |
| Booster Pump Set (High Zone) | 28 L/s @ 90 m head | B1 Plant Room | 1 (1 standby) |
| Pressure Reducing Valves | Set at 500 kPa | Each Floor Riser | 24 |
3.3 Pipe Sizing and Materials
Cold water distribution mains are CPVC Schedule 80 or Type L copper for sizes DN 25 and below. Risers DN 50 and above are Schedule 40 galvanized steel with mechanical couplings. All underground runs are HDPE DR-11, thermally fused.
| Pipe Section | Material | Size | Design Velocity (m/s) |
| Underground supply mains | HDPE DR-11 | DN 150 | 1.2 |
| Vertical risers – low zone | Galvanized Steel Sch. 40 | DN 100 | 1.5 |
| Vertical risers – high zone | Galvanized Steel Sch. 40 | DN 80 | 1.5 |
| Branch mains (per floor) | CPVC Sch. 80 | DN 50 | 1.0 |
| Fixture connections | Type L Copper | DN 15 – DN 25 | 0.8 |
4. Hot Water System
4.1 Hot Water Demand
Hot water demand is calculated at 45% of peak cold water fixture units per ASHRAE 90.1-2019 and BNBC 2020 residential standards. Design hot water delivery temperature is 60°C at the heater and 55°C at the most remote fixture to prevent Legionella growth, per WHO guidelines.
| Zone | Peak HW Demand (L/s) | Storage Required (L) | Recovery Rate (L/h) |
| Residential – Floors 5–14 | 8.2 | 12,000 | 3,800 |
| Residential – Floors 15–24 | 6.4 | 9,600 | 3,200 |
| Commercial / F&B | 3.4 | 5,000 | 2,000 |
| Total | 18.0 | 26,600 | 9,000 |
4.2 Hot Water Plant
Hot water is generated by gas-fired storage water heaters with stainless steel inner tanks and polyurethane foam insulation. A dedicated hot water recirculation loop maintains delivery temperature within 2°C of set point throughout all occupied periods.
• Gas-fired water heaters: 4 × 250 L capacity, 90 kW input each
• Recirculation pump: 0.8 L/s at 30 kPa, with variable-speed drive
• Thermostatic mixing valves set at 50°C for residential fixtures
• Temperature and pressure relief valves per ANSI Z21.22
• Drain pans and floor drains beneath all storage units
5. Sanitary Drainage System
5.1 System Design Basis
The sanitary drainage system is designed as a single-stack soil-waste-vent system per IPC 2021, with separate venting provisions. The primary soil stack is DN 150 from basement to roof level, transitioning to DN 100 branches at each floor. All drainage is gravity-fed to the municipal sewer connection at Basement Level 2.
5.2 Drainage Fixture Units (DFU) Summary
| Floor Range | Total DFU | Stack Size Required | Vent Stack Size |
| Roof – Floor 20 | 820 DFU | DN 100 | DN 75 |
| Floor 19 – Floor 10 | 1,640 DFU | DN 125 | DN 100 |
| Floor 9 – Floor 2 | 2,460 DFU | DN 150 | DN 100 |
| Ground – Basement | 3,100 DFU | DN 200 | DN 125 |
5.3 Pipe Materials and Slope
All sanitary drain piping within the building is cast iron soil pipe (CISPI 301) with hub-and-spigot joints above slab and no-hub couplings in concealed locations. Underground building drains are PVC SDR 35. Minimum horizontal drain slope is 1:50 (2%) for DN 100 and larger; 1:40 (2.5%) for DN 75 and smaller.
• Stacks: Cast iron, hubless with neoprene gaskets
• Horizontal branches: Cast iron, minimum 2% slope
• Underground: PVC SDR 35, minimum 1% slope
• Grease interceptors: Commercial kitchen lines routed through 1,500 L grease trap prior to connection to building drain
• Floor drains: DN 100 P-trap with trap primer in mechanical and parking areas
6. Storm Drainage System
6.1 Rainfall Design Criteria
Storm drainage has been designed for the 25-year return period rainfall intensity applicable to Dhaka, Bangladesh, in accordance with BNBC 2020 Chapter 7. Design intensity is 125 mm/hr for roof drainage and 100 mm/hr for surface areas.
| Drainage Area | Area (m²) | Runoff Coeff. | Design Flow (L/s) |
| Roof – Flat membrane | 2,400 | 0.95 | 79.2 |
| Terraces / Podium Deck | 800 | 0.85 | 23.6 |
| Surface Parking & Access | 1,200 | 0.80 | 26.7 |
| Landscaped Areas | 400 | 0.35 | 3.9 |
| Total Design Flow | 4,800 | — | 133.4 |
6.2 Roof Drainage
Roof drainage employs a primary gravity system with 100 mm cast iron roof drains at a maximum spacing of 20 m, connected to vertical DN 100 – DN 150 leaders routed inside the building core. Secondary overflow scuppers are provided at 150 mm above the roof membrane surface per IPC Section 1108.
• Primary drains: 8 no. × DN 100 roof drains at 20 m centres
• Overflow scuppers: Minimum 200 mm wide at parapet walls
• Vertical leaders: DN 150 cast iron to storm chamber
• Sump pump (B2): 2 × 45 L/s submersible pumps for below-grade drainage
6.3 Rainwater Harvesting
A rainwater harvesting system is incorporated to reduce potable water consumption for toilet flushing and irrigation. Collected rooftop runoff is filtered, stored, and UV-disinfected before distribution through a dedicated non-potable purple-pipe system.
| Component | Specification |
| Collection area | 1,800 m² treated roof area |
| First-flush diverter | 1.5 L/m² diverter volume |
| Filtration | 100 micron cartridge + activated carbon |
| UV Disinfection | 30 mJ/cm² minimum dose |
| Storage tank | 60 m³ HDPE underground cistern |
| Annual savings estimate | ~8,200 m³/year (18% of total demand) |
7. Natural Gas Distribution System
7.1 Gas Demand Calculations
Natural gas demand has been calculated in accordance with NFPA 54 and the gas utility requirements of Titas Gas Transmission and Distribution Company. All appliance ratings have been obtained from equipment schedules and manufacturer data sheets.
| Appliance / Zone | Quantity | Input (kW each) | Total Load (kW) |
| Gas-fired water heaters | 4 | 90 | 360 |
| Kitchen ranges – F&B | 12 | 18 | 216 |
| Commercial cook tops | 6 | 24 | 144 |
| Residential ranges | 240 | 8 | 1,920 |
| Gas boilers (backup) | 2 | 120 | 240 |
| Total Connected Load | — | — | 2,880 |
| Demand Factor Applied (0.45) | — | — | 1,296 |
7.2 Pipe Sizing and System Layout
The medium-pressure gas main (250 kPa) enters at Basement Level 2 via a utility meter station. Pressure is regulated to 1.75 kPa (low pressure) for distribution within the building via two-stage regulation. Gas piping is Schedule 40 black steel with welded joints, coated and wrapped underground.
• Service entry: DN 100 black steel, welded
• Building main riser: DN 80 black steel
• Residential branches: DN 25 – DN 32 black steel
• Commercial kitchen branches: DN 40 – DN 50 black steel
• Emergency shut-off valves: Seismically activated, at building entry and each floor
• Leak detection: Continuous gas monitoring in plant rooms and kitchens
8. Sustainability and Water Conservation
The plumbing design incorporates multiple water and energy conservation strategies targeting a 35% reduction in potable water consumption relative to a baseline building per LEED v4.1 prerequisites.
| Strategy | Standard Baseline | Design Performance | Savings (%) |
| Low-flow WC (4.8 L/flush) | 6.0 L/flush | 4.8 L/flush | 20% |
| Low-flow showerheads | 9.5 L/min | 5.7 L/min | 40% |
| Sensor lavatory faucets | 8.3 L/min | 1.9 L/min | 77% |
| Rainwater harvesting | Potable flush | Non-potable flush | 18% |
| Hot water recirculation | No recirc | Insulated loop + VSD | 15% HW energy |
| Composite annual savings | 458 m³/day | 298 m³/day | 35% |
9. Equipment Schedule
The following major plumbing equipment is incorporated in the design. Contractor shall verify all dimensions and utility requirements prior to procurement.
| Tag | Description | Capacity / Rating | Location | Qty |
| CWT-1 | Underground Cold Water Cistern | 200 m³ each | B2 Plant Room | 2 |
| RWT-1 | Rooftop Gravity Tank | 80 m³ each | Roof | 2 |
| BP-1 | Booster Pump – Low Zone | 42 L/s @ 45 m | B1 Plant Room | 2 |
| BP-2 | Booster Pump – High Zone | 28 L/s @ 90 m | B1 Plant Room | 2 |
| HW-1 | Gas Storage Water Heater | 250 L / 90 kW | B1 Plant Room | 4 |
| HWR-1 | HW Recirculation Pump | 0.8 L/s / VSD | B1 Plant Room | 2 |
| GI-1 | Grease Interceptor | 1,500 L | B1 | 1 |
| RHT-1 | Rainwater Harvest Tank | 60 m³ | B2 | 1 |
| UV-1 | UV Disinfection Unit | 30 mJ/cm² | B1 Utility | 1 |
| SP-1 | Sump Pump (B2) | 45 L/s, submersible | B2 Sump | 2 |
| PRV-1 | Pressure Reducing Valve | Set: 500 kPa | Each floor riser | 24 |
| MR-1 | Gas Meter & Regulator Set | 250 kPa → 1.75 kPa | B2 Meter Room | 1 |
10. Testing, Commissioning, and Inspection
10.1 Pressure Testing Requirements
All plumbing systems shall be tested in accordance with IPC 2021 Chapter 3 and the requirements of the local authority. Testing shall be witnessed by the Engineer of Record and documented in commissioning reports.
| System | Test Medium | Test Pressure | Duration | Acceptance |
| Water supply – above ground | Water | 1.5× working pressure min. 860 kPa | 30 min | No leaks or drops |
| Water supply – underground | Water | 1,200 kPa | 2 hrs | No leaks or drops |
| Sanitary drain/waste/vent | Water | 3 m head (fill stack) | 15 min | No visible leaks |
| Gas piping – low pressure | Air / Nitrogen | 345 kPa | 30 min | No pressure drop |
| Gas piping – medium pressure | Air / Nitrogen | 690 kPa | 60 min | No pressure drop |
| Storm drainage | Water | Fill roof drains | 15 min | No leaks / overflow |
10.2 Commissioning Checklist
Prior to system handover, the following commissioning activities shall be completed, documented, and submitted to the owner:
• Flushing and disinfection of all potable water systems per AWWA C651
• Water quality testing: turbidity, pH, chlorine residual, coliform bacteria
• Booster pump performance verification: flow, pressure, and power draw
• PRV calibration and lockout at design set point
• Hot water temperature verification at furthest fixture (minimum 55°C)
• Recirculation loop balancing and pump curve verification
• Grease interceptor inspection and baseline grease sample
• Gas leak survey with calibrated combustible gas detector
• Emergency gas shut-off valve function test
• UV disinfection unit validation per NSF/ANSI 55
• Roof drain flow test and overflow scupper function check
• Sump pump level control and alarm test
• BMS integration: sensor readings confirmed against local gauges
11. Plumbing Drawing Schedule
| Drawing No. | Title | Scale | Revision |
| PL-001 | Plumbing Legend, Notes and Abbreviations | N/A | Rev. 0 |
| PL-100 | Site Plumbing – Water Service and Storm | 1:500 | Rev. 0 |
| PL-101 | Basement B2 – Plumbing Plan | 1:100 | Rev. 0 |
| PL-102 | Basement B1 – Plumbing & Mechanical Plan | 1:100 | Rev. 0 |
| PL-103 | Ground Floor – Plumbing Plan | 1:100 | Rev. 0 |
| PL-104 | Typical Residential Floor Plan (Floors 5–24) | 1:100 | Rev. 0 |
| PL-200 | Cold Water Riser Diagram – Low Zone | N/A | Rev. 0 |
| PL-201 | Cold Water Riser Diagram – High Zone | N/A | Rev. 0 |
| PL-202 | Hot Water & Recirculation Riser Diagram | N/A | Rev. 0 |
| PL-300 | Sanitary Drainage Riser Diagram – Tower | N/A | Rev. 0 |
| PL-301 | Storm Drainage Riser and Roof Plan | N/A | Rev. 0 |
| PL-400 | Natural Gas Riser Diagram | N/A | Rev. 0 |
| PL-500 | Rainwater Harvesting Schematic | N/A | Rev. 0 |
| PL-600 | Plant Room – Water Storage & Booster | 1:50 | Rev. 0 |
| PL-700 | Plumbing Details and Sections | Various | Rev. 0 |
12. References and Appendices
12.1 Design References
• Bangladesh National Building Code (BNBC) 2020, Ministry of Housing and Public Works
• International Plumbing Code (IPC) 2021, International Code Council
• International Mechanical Code (IMC) 2021, International Code Council
• ASHRAE Standard 90.1-2019, Energy Standard for Buildings Except Low-Rise Residential
• ASHRAE Handbook – HVAC Applications, 2019 Edition, Chapter 50: Plumbing
• NFPA 54: National Fuel Gas Code, 2021 Edition
• NFPA 13: Standard for the Installation of Sprinkler Systems, 2022 Edition
• WHO Guidelines for Drinking-Water Quality, 4th Edition, 2017
• AWWA C651-14: Disinfecting Water Mains
• NSF/ANSI 55: Ultraviolet Microbiological Water Treatment Systems
• LEED v4.1 BD+C: Water Efficiency Credit Requirements
12.2 Appendices
The following appendices are attached to this report:
| Appendix | Content |
| A | Fixture Unit Count Worksheets – All Floors |
| B | Pipe Sizing Calculations – Water Supply and Drainage |
| C | Gas Load Calculations and Pipe Sizing Tables |
| D | Rainwater Harvesting Yield and Demand Analysis |
| E | Equipment Data Sheets and Submittals |
| F | Water Quality Test Protocol |
| G | Commissioning Forms and Checklists |
— END OF REPORT —
Prepared by: M. Ahmed, PE | Civil & Environmental Engineer | March 2025
Confidential | For Construction Use OnlyPage