This chapter collects all reference data tables, standards citations, unit conversions, and a glossary of technical terms used throughout the book. It is designed to be consulted during design work.
| Country/Region | Primary source | Notes |
|---|---|---|
| France | Météo-France (meteofrance.fr); DRIAS portal for climate projections | Download historical monthly data by station |
| UK | Met Office (metoffice.gov.uk/climate/uk); Environment Agency | National Rainfall Archive; 30-year averages available |
| Germany | DWD (dwd.de) | Climate data portal; station data download |
| Spain | AEMET (aemet.es) | Spanish meteorological agency |
| Italy | ISPRA; regional environmental agencies | Variable by region |
| Australia | Bureau of Meteorology (bom.gov.au) | Climate data online; 1901–present monthly data by station |
| USA | NOAA NCEI (ncei.noaa.gov) | Climate Data Online; US Climate Normals (30-year averages) |
| Global | ERA5 reanalysis (Copernicus CDS) | 0.25° gridded data since 1940; useful for remote locations |
| Global | WorldClim (worldclim.org) | 1 km resolution monthly averages |
Key parameters to download: Monthly mean rainfall (mm), monthly 10th percentile (dry year), monthly 90th percentile (wet year).
| Roof/Surface Material | Runoff Coefficient C | Notes |
|---|---|---|
| Smooth metal (zinc, steel, aluminium) | 0.90–0.95 | Best collection efficiency |
| Stainless steel | 0.92–0.96 | — |
| Vitrified clay tile (new) | 0.85–0.92 | |
| Vitrified clay tile (aged, mossy) | 0.75–0.85 | Moss increases absorption and contamination |
| Concrete tile (new) | 0.80–0.87 | |
| Concrete tile (aged) | 0.70–0.80 | Weathered concrete is more absorptive |
| Slate | 0.80–0.90 | |
| Bituminous felt (EPDM) — flat | 0.70–0.80 | Some VOC leaching when new |
| Concrete flat roof | 0.65–0.75 | Higher surface absorption |
| Asphalt flat roof | 0.70–0.80 | — |
| Fibre cement / corrugated asbestos | 0.75–0.85 | Do not collect from asbestos-containing materials |
| Green roof — extensive (sedum) | 0.15–0.40 | Highly saturated after prolonged rain: C approaches 0.4 |
| Green roof — intensive | 0.05–0.25 | Deep growing medium; high retention |
| Gravel path/driveway | 0.15–0.35 | — |
| Impermeable concrete/asphalt (ground) | 0.85–0.95 | Note: ground-level collection not covered in this book |
Hazen-Williams C values for common pipe materials:
| Material | C_HW |
|---|---|
| PVC-U (smooth) | 150 |
| CPVC | 150 |
| PEX (cross-linked polyethylene) | 150 |
| HDPE / MDPE | 150 |
| Copper (new) | 135 |
| Copper (5 years old) | 125 |
| Galvanised steel (new) | 120 |
| Galvanised steel (5 years) | 100 |
| Cast iron (new) | 130 |
| Cast iron (25 years) | 90 |
| Ductile iron (cement lined) | 140 |
Velocity limits for residential distribution:
| Appliance / Fixture | Volume per use | Frequency (typical) | Daily (household, 4 persons) |
|---|---|---|---|
| Toilet — dual flush, full | 6 L/flush | 2/person/day | 48 L |
| Toilet — dual flush, half | 3 L/flush | 3/person/day | 36 L |
| Toilet — old single flush | 9–13 L/flush | 5/person/day | 200–260 L |
| Shower — standard | 8 L/min, 8 min | 1/person/day | 256 L |
| Shower — low-flow | 6 L/min, 8 min | 1/person/day | 192 L |
| Bath | 175 L/event | 2/household/week | ~50 L |
| Washing machine — front-load modern | 50 L/cycle | 5 cycles/week | 36 L |
| Washing machine — top-load old | 130 L/cycle | 5 cycles/week | 93 L |
| Dishwasher — A-rated | 10 L/cycle | 1/day | 10 L |
| Kitchen sink (food prep + washing) | 40 L/day (household) | — | 40 L |
| Bathroom sinks | 18 L/person/day | — | 72 L |
| Garden irrigation (drip) | 3 L/m²/event | 3×/week | varies |
| Garden irrigation (sprinkler) | 7 L/m²/event | 2×/week | varies |
| Car washing (hose) | 300 L/wash | Monthly | ~10 L (avg) |
| Parameter | WHO Guideline Value |
|---|---|
| E. coli | 0 CFU/100 mL |
| Total coliforms | 0 CFU/100 mL |
| Turbidity | <1 NTU (ideally); <4 NTU (acceptable) |
| pH | 6.5–8.5 |
| TDS | <600 mg/L (aesthetic) |
| Nitrate (NO₃⁻) | 50 mg/L |
| Nitrite (NO₂⁻) | 3 mg/L |
| Fluoride | 1.5 mg/L |
| Arsenic | 10 μg/L |
| Lead | 10 μg/L |
| Copper | 2,000 μg/L |
| Zinc | 3,000 μg/L |
| Manganese | 100 μg/L |
| Chlorine residual | 0.2–0.5 mg/L (recommended for distribution residual) |
Generally aligned with WHO; key additions:
| Formula | Application | Units |
|---|---|---|
V = A × R × C |
Rainwater collection yield | L (A in m², R in mm, C dimensionless) |
S(t) = S(t-1) + Inflow - Demand |
Tank mass balance | L |
P = ρgH |
Head pressure | kPa (ρ=1000, g=9.81, H in m) |
h_f = 10.67 L Q^1.852 / (C^1.852 D^4.87) |
Hazen-Williams friction loss | m (Q in m³/s, D in m) |
TDH = Δz + h_f + P_delivery/ρg |
Total dynamic head | m |
P_pump = ρgQH / η |
Pump electrical power | W |
Dose = I × t |
UV disinfection dose | mJ/cm² (I in mW/cm², t in s) |
mL_bleach = target_mg_L × V_L / 2500 |
Shock chlorination (5% bleach) | mL bleach per L tank volume |
SAR = Na / sqrt((Ca+Mg)/2) |
Sodium adsorption ratio | — (concentrations in mmol/L) |
Payback = CAPEX / (Savings - OPEX) |
Simple payback | years |
NPV = Σ(CF_t / (1+r)^t) - CAPEX |
Net present value | € |
| Quantity | From | To | Factor |
|---|---|---|---|
| Volume | 1 liter (L) | m³ | × 0.001 |
| Volume | 1 m³ | Liters | × 1,000 |
| Volume | 1 UK gallon | Liters | × 4.546 |
| Volume | 1 US gallon | Liters | × 3.785 |
| Rainfall | 1 mm on 1 m² | Liters | = 1 L |
| Rainfall | 1 m on 1 m² | m³ | = 1 m³ |
| Pressure | 1 bar | kPa | × 100 |
| Pressure | 1 bar | m of water head | × 10.2 |
| Pressure | 1 kPa | m of water head | × 0.102 |
| Pressure | 1 psi | kPa | × 6.895 |
| Flow rate | 1 L/min | m³/s | × 1.667 × 10⁻⁵ |
| Flow rate | 1 L/hr | m³/day | × 0.024 |
| Energy | 1 kWh | MJ | × 3.6 |
| Standard | Scope | Jurisdiction |
|---|---|---|
| BS 8515:2009+A1:2013 | Rainwater harvesting systems — Code of Practice | UK |
| BS 8525-1:2010 | Greywater systems Part 1: Code of Practice | UK |
| BS EN 1717:2000 | Protection against pollution of potable water — backflow prevention | EU/UK |
| DIN 1986-100 | Drainage systems in buildings | Germany |
| DIN EN 12056 | Gravity drainage systems inside buildings | EU/Germany |
| AS/NZS 3500.1 | Plumbing and drainage — Water services | Australia |
| NSF/ANSI 350 | Onsite residential and commercial water reuse treatment systems | USA |
| ISO 24512 | Service activities relating to drinking water supply systems | International |
| WHO 2017 | Guidelines for Drinking-water Quality (4th edition) | International reference |
| EU 2020/2184/EU | EU Drinking Water Directive | EU |
Aerobic: Biological process occurring in the presence of oxygen.
Air gap: Physical separation between a pipe outlet and the overflow level of a receiving vessel, preventing back-siphonage.
Anaerobic: Biological process occurring without oxygen; produces sulfide gases and odour in stagnant water.
Aquifer: Underground layer of permeable rock or sediment that holds and transmits groundwater.
Backflow: Unwanted reversal of water flow, which can allow non-potable water to enter the potable supply.
Biochemical Oxygen Demand (BOD): Amount of dissolved oxygen needed by microorganisms to decompose organic matter in water; measure of organic pollution load.
Blackwater: Wastewater containing fecal matter from toilets; requires full sewage treatment.
Constructed wetland: An engineered system that mimics natural wetland processes for water treatment.
Cross-connection: Physical link between a potable water supply and a non-potable source.
Depth of Discharge (DoD): Fraction of battery capacity that can be safely discharged; 0.8 for LiFePO4, 0.5 for lead-acid.
First-flush diverter: Device that diverts the initial, most contaminated portion of roof runoff away from storage, then allows cleaner water to enter the tank.
Greywater: Wastewater from baths, showers, sinks, and washing machines — not including toilet waste.
Head: Pressure expressed as the height of a water column; 1 meter of head ≈ 9.8 kPa ≈ 0.098 bar.
Hazen-Williams coefficient (C_HW): Empirical constant characterising pipe roughness; higher = smoother = less friction.
HDPE: High-density polyethylene; material for food-grade water storage tanks and buried supply pipes.
IBC: Intermediate Bulk Container; 1,000 L plastic container in steel cage, originally for industrial bulk liquids.
Levelized Cost of Water (LCW): Total cost (capital + operating) divided by total water produced over system life; expressed in €/m³ or £/m³.
MPPT: Maximum Power Point Tracking; controller algorithm that optimises power extraction from a solar panel.
Non-potable water: Water not safe for drinking or food preparation; suitable for toilet flushing, irrigation, and industrial uses.
NTU: Nephelometric Turbidity Units; measure of water cloudiness. WHO guideline for drinking water: <1 NTU.
NPV: Net Present Value; difference between the present value of cash inflows and outflows over a period; positive NPV means financially beneficial.
Potable water: Water that meets drinking water quality standards; safe for consumption by humans.
Rainwater harvesting: Collection and storage of rainfall, typically from rooftop surfaces.
Rippl method: Graphical/analytical technique for sizing a reservoir; finds minimum storage needed given known monthly supply and demand sequences.
Runoff coefficient: Fraction of precipitation that reaches the collection system, accounting for losses to absorption, evaporation, and splash.
SAR: Sodium Adsorption Ratio; measure of sodium relative to calcium and magnesium in irrigation water; high SAR degrades soil structure.
Soakaway: Underground infiltration structure that disperses excess water slowly into the surrounding soil.
TDH: Total Dynamic Head; total head a pump must provide, including static head, friction losses, minor losses, and delivery pressure.
TDS: Total Dissolved Solids; measure of dissolved mineral content in water.
Total coliforms: Group of bacteria used as indicators of water contamination; includes E. coli and other species.
UV dose: Product of UV intensity (mW/cm²) and exposure time (seconds); expressed in mJ/cm²; 30–40 mJ/cm² required for potable disinfection.
Technical Standards and Codes:
Books:
Online Tools:
Organisations:
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