Drain Flow Rate Calculator

Results

  • Flow Rate: 0 GPM
  • Flow Velocity: 0 ft/s
  • Flow Capacity: 0 %
  • Hydraulic Radius: 0 inches
  • Cross-sectional Area: 0 sq inches
  • System Rating: -

Understanding Drain Flow

Drain flow rate affects system performance.

  • Manning's Equation Flow calculation basis.
  • Slope Gravity effect.
  • Roughness Material friction.
  • Capacity Maximum flow.

Design Guidelines

Sizing

Proper capacity.

Slope

Adequate flow.

Material

Surface friction.

Velocity

Self-cleaning.

Hydraulic Principles

  • Flow Characteristics Manning's equation: Q = (1.49/n)AR^(2/3)S^(1/2). Froude number: 0.7-1.2. Critical depth: yc = (q²/g)^(1/3). Energy grade line: 0.2-0.5%.
  • Velocity Parameters Minimum self-cleaning: 2.0 ft/s. Maximum allowable: 10 ft/s. Transitional flow: Re 2000-4000. Entrance loss coefficient: 0.5-1.0.
  • Capacity Factors Full flow efficiency: 0.85-0.95. Roughness height: 0.0002-0.006 ft. Form factor: 0.75-0.85. Hydraulic radius ratio: 0.5-0.8.

Design Standards

  • System Requirements Design storm: 10-year return. Peak flow factor: 1.5-2.0. Minimum diameter: 4". Maximum length: 100× diameter. Cleanout spacing: 50-75'.
  • Performance Metrics Head loss gradient: 0.01-0.05 ft/ft. Surcharge tolerance: 1.2× diameter. Overflow capacity: 1.5× design flow. System resilience: 25-year event.
  • Safety Margins Design factor: 1.25-1.5. Freeboard: 20% of diameter. Emergency overflow: 2× peak flow. Structural safety: FS 2.0. Bedding factor: 1.5-1.9.

Flow Analysis

  • Measurement Methods Flow meter accuracy: ±2%. Pressure head: ±0.1 ft. Velocity profile: log-law distribution. Time-averaging: 5-minute intervals.
  • Calculation Parameters Kinematic viscosity: 1.31×10⁻⁵ ft²/s. Surface tension: 0.005 lb/ft. Specific weight: 62.4 lb/ft³. Bulk modulus: 300,000 psi.
  • Quality Control Calibration frequency: quarterly. Data validation: 95% confidence. Measurement points: 5× diameter spacing. Repeatability: ±1%.

Environmental Considerations

  • Treatment Standards BOD removal: 85-95%. TSS reduction: 90-98%. Nutrient removal: 40-60%. Pathogen reduction: 99.9%. Heavy metals: <0.1 mg/L.
  • Monitoring Requirements pH range: 6.0-9.0. Temperature: 10-25°C. Dissolved oxygen: >2 mg/L. Conductivity: <2000 μS/cm. Turbidity: <5 NTU.
  • Sustainability Metrics Energy efficiency: 0.3-0.5 kWh/m³. Carbon footprint: <0.5 kg CO₂e/m³. Chemical usage: <50 g/m³. Water reuse potential: 60-80%.