DM Sewerage Design Guidelines
Dubai Municipality — Waste & Sewerage Agency | Document DM-WSA-SRPD-SEW2
Sewerage Design Guidelines
— Complete Summary
Comprehensive reference guide for design consultants, contractors, and developers when planning, designing, and constructing conventional foul water gravity sewers, property connections, pumping stations, rising/pressure mains, and sewerage treatments in Dubai Emirate.
This guide is for use by design consultants, contractors, and developers when planning, designing, and constructing the conventional foul water gravity sewers, property connections, pumping stations, rising/pressure mains, and sewerage treatments in Dubai Emirate intended to be part of Dubai Municipality sewerage system.
There shall be no deviation from these guidelines except where formally confirmed by DM in writing; such deviation must be technically justified or represent advances in knowledge or technology.
DM is committed to using new and innovative technologies where they represent the best technical solution, provide low life cycle costs and value for money. All technologies will be considered providing they have been proven in terms of performance, quality, and cost.
The Consultant shall submit the design document to DM for review and approval. Design stage-wise requirements will be collected from DM before submission. DM reserves the right not to approve connections that fail to meet minimum standards.
Engineers and other disciplines using this Design Guidelines must be experienced and appropriately qualified professionals familiar with planning, design, construction, operation, and maintenance of drainage networks.
All inquiries regarding the DM Sewerage Guidelines shall be sent to DM's official incoming email: dm@dm.gov.ae — copying the SRPD Director and the Head of Projects Planning and Development Section.
The designer shall collect all relevant information including digital mapping, future development plans, existing sewerage assets, other utility assets, hydrological information, current and projected populations, and per capita consumption information.
| Sr. | Asset Type | Minimum Design Life |
|---|---|---|
| 1 | Pipelines | 60 years |
| 2 | Structures | 50–60 years |
| 3 | Mechanical and Electrical Equipment | 15 years |
| 4 | Instrumentation, Computer Hardware, and Sensors | 5 years |
A plan maintenance schedule and spare parts list shall be submitted as part of the design submission. During NPV analysis, the cost for maintenance and replacement of equipment shall be considered.
- Geotechnical and groundwater investigations
- Topography survey
- Bathymetric survey
- Salinity monitoring
- Flow monitoring
- Environmental studies (e.g., hydrodynamic modelling)
- Hazardous Area Zoning classification
- Local regulatory compliance (DCD, DM, JAFZA, DEWA)
- Minimize confined space entry
- Safe access for all plant requiring maintenance
- Facilities secured and inaccessible to public
- Adequate lifting facilities for heavy equipment
- Adequate lighting for O&M
- Flow isolation and overflow facilities
Value engineering is mandatory to enhance the value of a project by structurally examining decisions about benefits, risks, and costs. VE workshops with DM shall be arranged throughout the project from concept to detail design stages.
Each option shall be evaluated covering: Sustainability Adaptability Feasibility Operability Constructability Financial Environment
The estimated sewage generation shall be approximately 80% of potable water demand as established by DEWA. An equivalent sewage generation rate of 280 litres/capita/day shall generally be used.
1. Current Population Data — Dubai Statistical Centre
2. Dubai Structure Plan Population — DM Planning Department
3. Ultimate Holding Capacity — DM Planning Department
3.1.2.1 Residential Sewage Generation Rates
| Development Type | DEWA Water Demand Range (L) | Typical Water Demand (L) | Avg Daily Sewage Flow |
|---|---|---|---|
| Low Cost Residential | 250–400 | 250 | 200 L/day/capita |
| Medium Cost Residential | 250–400 | 280 | 225 L/day/capita |
| High Cost Residential | 250–400 | 350 | 280 L/day/capita |
| Villas | 250–400 | 400 | 320 L/day/capita |
| High Rise | 250–400 | 350 | 280 L/day/capita |
| Labour Accommodation | 80–150 | 150 | 120 L/day/capita |
3.1.2.2 Institutional Area Flows
| Source | Unit | Range (L/Unit-day) | Typical |
|---|---|---|---|
| Hospital (Medical) | Bed | 500–900 | 600 |
| Hospital (Mental) | Bed | 280–530 | 380 |
| Prison | Inmate | 280–570 | 450 |
| Rest Home | Resident | 190–450 | 320 |
| Schools (w/ cafeteria, gym & showers) | Student | 56–115 | 95 |
| Schools (w/ cafeteria only) | Student | 38–75 | 56 |
| Schools (no cafeteria/gym) | Student | 19–65 | 42 |
| Boarding School | Student | 190–380 | 280 |
3.1.2.3 Commercial Area Flows
| Source | Unit | Range (L/Unit-day) | Typical |
|---|---|---|---|
| Airport | Passenger | 7–11 | 11 |
| Hotel | Guest | 150–230 | 180 |
| Office | Employee | 26–60 | 49 |
| Restaurant | Meal | 8–15 | 11 |
| Shopping Centre | Employee | 26–49 | 38 |
| Department Store | Toilet Room | 1500–2300 | 1900 |
| Industrial (Sanitary only) | Employee | 26–60 | 50 |
| Laundry (Self-Service) | Machine | 250–1500 | 2100 |
| Dry Industry | Employee | 50 L at 8 per m² | |
The sewer network consists of Header sewers, Lateral sewers, Trunk sewers, and Main Collector sewers. All sewer designs shall be modelled using numerical software such as Sewer GEM, Info-SEWER, InfoSWMM or equivalent.
• Demarcation of sewer catchment based on topography
• Shortest pipe route alignment for economy
• Sufficient sewer depths for all existing and future properties
• Self-cleansing velocities at peak flow
• Adequate access for maintenance
• Septicity development avoidance
3.2.1 Peaking Factor
For Population ≤ 500 Peaking Factor = 5.0
3.2.3 Velocity Criteria
3.2.4 Depth of Flow — Maximum % Pipe Full at Peak Flow
| Pipe Diameter | Min d/D | Max d/D |
|---|---|---|
| Up to 500 mm | 0.50 | 0.70 |
| 500–800 mm | 0.50 | 0.65–0.70 |
| Greater than 800 mm | 0.50 | 0.65 |
V = velocity (m/s) | g = gravitational acceleration (m/s²)
D = internal pipe diameter (mm) | S = hydraulic gradient
Ks = effective roughness (mm) — Recommended: 1.5 mm
ν = kinematic viscosity (m²/s)
V = pipe velocity (m/s) | n = roughness coefficient — Recommended: 0.013
R = hydraulic radius (m) | S = slope of energy grade line (m/m)
Consideration shall be given to dynamic modelling in designing systems for more than 10,000 inhabitants.
Based on Self-Cleansing Velocity (0.75 m/s)
| Diameter (mm) | Min Gradient (mm/m) | Diameter (mm) | Min Gradient (mm/m) |
|---|---|---|---|
| 150 | 7.50 | 700 | 1.00 |
| 200 | 5.00 | 800 | 0.85 |
| 250 | 3.75 | 900 | 0.75 |
| 315 | 2.70 | 1000 | 0.65 |
| 400 | 2.05 | 1200 | 0.50 |
| 500 | 1.55 | 1400 | 0.45 |
| 600 | 1.25 | 1600 | 0.35 |
| 1800 | 0.30 | ||
| 2000+ | 0.25 | ||
Where self-cleansing velocity approach is not attainable at the head of sewerage systems, minimum pipe gradient shall be calculated based on minimum tractive force methodology. The steeper gradient of both methods shall be adopted.
| Category | Size Range | Construction Method | Preferred Materials |
|---|---|---|---|
| House Connections | Up to 200mm O.D. | Open Trench | uPVC MDPE HDPE |
| House Connections | Up to 200mm O.D. | Trenchless | GRP HDPE |
| Sewer Mains | 200–300mm | Open Trench | uPVC HDPE |
| Sewer Mains | 200–300mm | Trenchless | GRP HDPE |
| Sewer Mains | 350mm & Greater | Open Trench | GRP HDPE GRP/PVC lined RCC |
| Sewer Mains | 350mm & Greater | Trenchless | GRP HDPE |
| Type of Crossing | Min Cover / Clearance (m) |
|---|---|
| Without protection | 1.2 |
| With protection | 0.5 |
| Road crossing (non-destructive) | 2.5 |
| Under Water Pipeline (open cut) | 0.5 |
| Under Electricity / Telecom | 0.3 |
| Under Oil & Gas | Per DUSUP requirements |
Maximum recommended cover: 10–12 m. Minimum horizontal clearance: 3 m. Potable water main shall always be above the sewer main.
Manholes shall be provided at: Change in gradient Change in diameter Junctions Regular spacing End of lateral
Maximum Spacing Between Manholes
| Pipe Diameter | Maximum Spacing |
|---|---|
| ≤ 315 mm | 100 m |
| 350–500 mm | 150 m |
| 600–800 mm | 200 m |
| 900–1000 mm | 250 m |
| 1100–1300 mm | 300 m |
| 1400–1500 mm | 400 m |
| > 1500 mm | 600 m |
Manhole Cover Levels
| Location | Cover Level |
|---|---|
| Paved areas | Final Paved Level |
| Landscaped areas | Final Ground Level + 0.1 m |
| Open, unpaved areas | Final Ground Level + 0.25 m |
Backdrops required when difference in invert elevations exceeds 600 mm. External backdrops preferred. Internal backdrops only for new connections to existing manholes where external is not practicable. Not permitted on manholes < 1.5 m diameter.
- Future connection provision: A chamber at the boundary of each known plot for future connections (DM approval required)
- Stub pipes: Incorporated in selected manholes for system extension
- Chamber spacing: Between 20 m and 50 m where practical
- General arrangement: Each plot drains separately to an inspection chamber outside the boundary
Follow Federal Law for the protection and development of the environment and its executive order regarding hazardous materials, medical and radioactive wastes.
General Characteristics — Maximum Allowable Concentrations
| Substance | Unit | Max Allowable |
|---|---|---|
| Chemical Oxygen Demand (COD) | mg/L | 1000 |
| Total Suspended Solids (TSS) | mg/L | 500 |
| Total Dissolved Solids (TDS) | mg/L | 3000 |
| Temperature | °C | 45 |
| pH | unit | > 6 and < 9 |
| Grease & Oil (hydrocarbon) | mg/L | 60 |
| Grease & Oil (non-hydrocarbon) | mg/L | 100 |
| Max physical size of non-fecal matter | mm | 15 |
Inorganic Compounds
| Substance | Max (mg/L) | Substance | Max (mg/L) |
|---|---|---|---|
| Chloride (as Cl⁻) | 1000 | Sulphate (as SO₄) | 1000 |
| Cyanide (as CN) | 2 | Sulphide (as S) | 1 |
| Fluoride (as F⁻) | 15 | Total Kjeldahl Nitrogen | 150 |
| Total Phosphorus | 50 | ||
Metals — Maximum Allowable Concentrations
| Metal | Max (mg/L) | Metal | Max (mg/L) | Metal | Max (mg/L) |
|---|---|---|---|---|---|
| Aluminium | 100 | Iron | 50 | Nickel | 10 |
| Arsenic | 5 | Lead | 5 | Selenium | 10 |
| Barium | 10 | Lithium | 2.5 | Silver | 5 |
| Beryllium | 5 | Manganese | 10 | Tin | 10 |
| Boron | 5 | Mercury | 0.5 | Vanadium | 1 |
| Cadmium | 1 | Molybdenum | 10 | Zinc | 10 |
| Chromium (Total) | 5 | ||||
| Cobalt | 5 | ||||
| Copper | 5 |
Organic Compounds
| Substance | Unit | Max Allowable |
|---|---|---|
| Detergents (LAS as MBAS) | mg/L | 30 |
| Phenolic Compounds (as Phenol) | mg/L | 0.5 |
| Polycyclic Aromatic Hydrocarbons (PAH) | mg/L | 0.05 |
| Organophosphorus Pesticides | mg/L | 0.01 |
| Organochlorine Pesticides | mg/L | 0.01 |
Installed at the upstream end of property connections, upstream of grit separator or petrol interceptor.
| Flow (L/s) | 2 | 3 | 4 | 5 | 6 |
|---|---|---|---|---|---|
| Internal Dimensions (mm) | 1000×800 | 1400×800 | 1750×1000 | 2000×1000 | 2500×1000 |
| Min Capacity (L) | 520 | 840 | 1400 | 1800 | 2500 |
Car wash plants: Minimum 5,000 L capacity even when flow is under 6.0 L/s.
Required for restaurants, cafes, cafeterias, clubs, hotels, hospitals, factory/school kitchens.
- Sized by peak design flow rates with minimum 30-minute retention time
- Min liquid depth: 760 mm | Max liquid depth: 1800 mm
- Inlet pipe ≥ 100 mm diameter; invert difference: 50–100 mm
- Max pump-out interval: 12 weeks
- Minimum efficiency: 80%
- Water tightness test: Vacuum (100 mm Hg for 5 min) or Hydrostatic (8–10 hours)
- Vehicle washing: 2 L/s per wash line; separator sized at double the wastewater flow
- Light liquids retention: min 3 minutes up to 20 L/s (+1 min per 10 L/s increase)
- Vehicle maintenance bays (heavier liquids): 6–9 minutes retention
- Width to length ratio: 1:1.8
Acidic waste (pH below 6.0) collected and passed through Acid Neutralization & Monitoring System prior to discharge into public sewer. All acidic effluent gathered separately from non-acidic waste.
Fitted with removable wire basket preventing passage of solids ≥ 12.5 mm. Fitted at point in internal drainage network to prevent solid waste discharge to public sewer.
Installed within property boundary where customer's service drainage connects to public sewer. 'P' or 'Running' type providing water seal that aerially disconnects customer drain from public sewer. Prevents sewer gases from entering customer's drainage system. Owner responsible for construction and periodic maintenance.
For small to medium size facilities. Submersible close-coupled pumps driven by submersible motor, generally vertical installed type.
For large facilities. Centrifugal (non-clog) pump with horizontal or vertical shaft, frame-mounted or close-coupled with motor on dry chamber floor.
VFDs shall be considered for stations with wide variation in flow patterns and system pressure. VFDs minimize detention time in wet well and allow smaller wet well volumes.
Pump station and pressure main system designed on WLCC basis. Large diameter pipe = higher pipe cost but lower pump head & power. Small diameter = lower pipe cost but higher pump head & power.
| Station | Peak Factor | Station | Peak Factor | Station | Peak Factor |
|---|---|---|---|---|---|
| C | 1.27 | Q | 1.44 | X | 1.34 |
| E | 1.45 | H | 1.55 | I | 1.80 |
| G | 1.29 | S | 1.30 | ||
| K | 1.56 | Sn | 1.32 | ||
| X1 | 1.28 | ||||
| V | 1.36 |
V = storage volume between starts (m³)
Q = pump discharge rate (m³/sec)
t = time between starts (sec)
| Motor Power | Time Between Starts (t) |
|---|---|
| 0.75 – 30 kW | 10 minutes |
| 35 – 60 kW | 15 minutes |
| 65 – 300 kW | 20 minutes |
| > 300 kW | 30 minutes |
a) Total number of proposed pumps (duty + standby) ≥ 4, OR
b) Total peak design capacity ≥ 1000 L/s
- Option A: 2 pumps (1 duty + 1 standby), each 100% peak flow
- Option B: 3 pumps, each 50% peak flow (2 duty + 50% standby)
Number of duty and standby pumps chosen based on strategic importance. Must consider consequences of pump failure at peak flow or during maintenance.
5.1.6 Net Positive Suction Head (NPSH)
Hbar = Atmospheric Pressure (m)
Hs = Suction Head (m)
Hvap = Vapour Pressure of water (m)
HL = Head loss between wet well and pump impeller (m)
Design Criterion NPSHa > NPSHr (mandatory for all pump combinations)
- Wet wells isolated from dry wells by impermeable walls
- Independent ventilation systems
- Provisions for equipment removal
- Safe access to all areas
- Materials resistant to H₂S and corrosive gases
- Hazardous Zone classification for all equipment
- Dubai Civil Defence compliance
Acceptable technologies:
- Activated carbon filter
- Bio-scrubbers
- Chemical scrubber
- Ozonation
Design concentrations:
- Inlet H₂S average: 50 ppm
- Inlet H₂S peak: 300 ppm
- Outlet at discharge: < 1 ppm
Pipe Roughness Factor (Ks) — Colebrook-White
| Velocity (m/s) | Rough Pipe Ks (mm) | Smooth Pipe Ks (mm) |
|---|---|---|
| < 0.75 | 3.0 | 1.5 |
| 0.75 – 1.0 | 1.5 | 0.6 |
| 1.0 – 1.5 | 0.6 | 0.3 |
| 1.5 – 2.0 | 0.3 | 0.15 |
| > 2.0 | 0.15 | 0.10 |
Rough pipe: C = 120 | Smooth pipe (new): C = 140
Colebrook-White with velocity-dependent roughness is recommended for wastewater pressure mains.
System Resistance Curve — Mandatory Band
- a) Min Static Head + frictional loss (rough pipe condition)
- b) Max Static Head + frictional loss (rough pipe condition)
- c) Min Static Head + frictional loss (smooth pipe condition)
Material Selection
Within pumping station: Ductile Iron (or Stainless Steel for stations < 100 L/s)
Pressure main: Ductile Iron GRP HDPE
Air valves (double orifice type) required at:
- Downstream end of ascending length
- High points where main approaches then recedes from HGL
- Increases in downward gradient / decreases in upward gradient
- Intervals not exceeding 700 m on level or long descending stretches
Air Valve Sizing
| Pipeline Bore (mm) | Nominal Air Valve Size (mm) |
|---|---|
| ≥ 300 | 80 |
| 300–500 | 80–100 |
| 600–900 | 150 |
| 1000–1200 | 200 |
| 1300–1600 | 2 × 200 |
Washout Sizing
| Transmission Main | Washout Pipe |
|---|---|
| Up to 400 mm | 100 mm |
| 500–800 mm | 150 mm |
| 900–1200 mm | 200 mm |
| 1200 mm and above | 300 mm |
Drain valve sized to drain isolated section within 4 hours. Minimum washout diameter: 100 mm.
Water hammer/surge analysis is mandatory using software such as InfoSurge, Wanda, or Bentley Hammer. Software choice must be approved by DM prior to commencement.
ΔH = Change in Pressure (m) | c = Wave Propagation speed (m/s)
g = Acceleration due to gravity (m/s²) | ΔV = Change in flow Velocity (m/s)
High Pressure: May rupture pipelines, damage fittings
Low Pressure: May collapse pipeline
Reverse Flow: May damage pump seal, brush gear on motors
Pipeline Movement: May lead to overstressing and failure of supports
Pressure Criteria
- A. Vapour cavities and column separation shall NOT occur
- B. Min pressure ≤ allowable limit by pipe manufacturer OR max 0.2 bar below atmospheric (whichever is highest)
- C. Max pressure ≤ hydraulic test pressure OR rated max pressure of components (whichever is lowest)
Surge Suppression Options
- Pressurised surge arresting vessels (Total Volume ≥ Max expanded Volume + 20%)
- Non-Slam Air Valves (for smaller systems only)
- Bypass check valve from suction to delivery side
- Flywheel addition to pump (increase inertia, prolong run-down time)
- Regulating Valves (final option only — must be suitable for sewage)