Tank Sizing Methodology

Water supply tanks serve multiple purposes: storing potable water for periods of high demand or supply interruption, accommodating thermal expansion in closed systems, and maintaining pressure in pumped systems. Plumbing Booster's Water Supply Tanks & Vessels module handles four tank types in its first release.

**Potable Atmospheric**: Stores drinking water at atmospheric pressure. Sized based on daily demand, supply reliability, and reserve capacity. Used when municipal supply is intermittent or for buildings with high peak demand. **Fire Water (NFPA 22)**: Fire protection water storage per NFPA 22 standard. Sized based on fire suppression system demand, duration, and reliability requirements. Supports four NFPA 22 configurations: F1 (direct flow duration), F2 (demand source import), F3 (break tank), and F4 (pressure tank). **Pressure Tank**: Maintains pressure in pumped systems, reduces pump cycling. Sized based on pump capacity, cut-in/cut-out pressure differential, and drawdown volume requirements. Uses the formula: drawdown fraction = (P2 - P1) / (P2 + 14.7). **Irrigation Tank**: Stores water for irrigation systems. Sized based on area daily requirement, daily demand autonomy, peak demand refill balancing, or zone flow duration.

Plumbing Booster supports five potable atmospheric tank sizing methods: 1. **ASPE M1 (Fixture-Based)** - Uses fixture count and building type with ASPE Table 5-5 data. 2. **ASPE M2 (Gravity, Multiple Dwellings)** - Uses apartment count and people estimate with ASPE Figure 5-4. 3. **SEP Required Autonomy** - Uses daily demand, peak factor, autonomy duration, and backup flow. 4. **SEP Per Capita** - Uses per-capita consumption data by country/category. 5. **CIBSE G (Fixture Usage)** - Uses CIBSE fixture types and usage data. Each method produces a required volume with unit conversions, safety margins, freeboard allowances, and tank selection logic.

Four NFPA 22 configurations are supported: 1. **F1 (Direct Flow Duration)** - Fire flow multiplied by duration. 2. **F2 (Demand Source Import)** - Imports from sprinkler, standpipe, or hydraulic sources. 3. **F3 (Break Tank)** - Pump capacity x break factor x duration - refill supply. 4. **F4 (Pressure Tank)** - Water volume + air volume with air-to-water ratio. Fire hazard classifications: light, ordinary-1, ordinary-2, extra-1, extra-2, special. Fire tank functions: gravity, suction, pressure, break-tank. Fire tank construction: welded-steel, bolted-steel, wood, embankment-fabric, concrete, frp.

The Water Supply Tanks module: 1. Select tank type (potable-atmospheric, fire-water-nfpa22, pressure-tank, irrigation-tank). 2. Select sizing method (varies by tank type). 3. Enter demand and system parameters. 4. The software calculates required volume, applies safety margins and freeboard, and selects from standard tank sizes. 5. For fire water, NFPA 22 requirements are applied with advisory checks for duration, refill time, and compliance. 6. Results show tank volume, dimensions, advisories, and unit preference summaries. 7. Per-quantity unit preferences are supported (user chooses preferred units for volume, pressure, etc.).