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Rainwater Harvesting Verification Checklist

Essential Checklist+

Complete these critical checks before approving the work or proceeding to the next construction stage.

✓19 Inspection Points
✓5 Verification Categories
✓Catchment Area+
  • Catchment area was measured as the plan (horizontal) area of the roof — not the slope area of pitched roofs.
  • All roof surfaces draining to the collection system were included — multiple slopes and sections were summed.
  • Surfaces that do not drain to the collection point — walls, adjacent roofs, skylights draining internally — were excluded.
  • Dimensions were entered in consistent units.
✓Rainfall Data+
  • Rainfall data was obtained from the IMD (India Meteorological Department) or local authority for the specific location — not a regional average.
  • Annual rainfall was split into monthly data to identify dry months and size storage accordingly — annual average alone is insufficient for sizing.
  • For recharge pit sizing, the 1-hour peak rainfall intensity (mm/hr) for the location was obtained — not the annual total.
✓Runoff and Collection Efficiency+
  • Runoff coefficient was set appropriately for the roof material — RCC terrace 0.85–0.95, clay tile 0.75–0.90, corrugated sheet 0.70–0.90.
  • First-flush diverter volume was calculated and a first-flush device was specified — first 2.5mm of rainfall per 100 m² catchment is diverted.
  • Collection efficiency factor of 0.70–0.85 was applied to account for evaporation, spillage, and first-flush losses.
  • Gutters and downpipes were sized to carry peak rainfall intensity without overflow — undersized gutters lose runoff before it reaches the tank.
✓Storage Tank Sizing+
  • Storage tank volume was sized for the longest dry period in the local rainfall pattern — not the annual total.
  • Daily demand for the intended end use (toilet flushing, irrigation, car washing) was calculated and used as the drawdown rate.
  • Rainwater harvesting is not intended for drinking without treatment — end use was confirmed as non-potable.
  • Overflow from the storage tank was directed to a soak pit or municipal drain — not to a neighbour's property.
  • For groundwater recharge pits, the soil permeability (infiltration rate) was confirmed — clay soil cannot absorb at the required rate.
✓Regulatory and Maintenance+
  • Local municipal or state authority rainwater harvesting bye-law requirements were confirmed — several Indian cities mandate RWH for plots above a minimum size.
  • Recharge pit location is at least 15m from any septic tank or soak pit to prevent groundwater contamination.
  • Structural adequacy of the terrace for the additional water load during peak rainfall was confirmed with the structural engineer.
Full QC Checklist+

Verify catchment, rainfall, runoff, first flush, storage, overflow, and maintenance.

✓27 Inspection Points
✓5 Verification Categories
✓Catchment Area+
  • Catchment area was measured as the plan (horizontal) area of the roof — not the slope area of pitched roofs.
  • All roof surfaces draining to the collection system were included — multiple slopes and sections were summed.
  • Surfaces that do not drain to the collection point — walls, adjacent roofs, skylights draining internally — were excluded.
  • For terraced roofs, the net area was used after deducting parapet wall footprint, AC units, and overhead tank base.
  • Dimensions were entered in consistent units.
✓Rainfall Data+
  • Rainfall data was obtained from the IMD (India Meteorological Department) or local authority for the specific location — not a regional average.
  • Annual rainfall was split into monthly data to identify dry months and size storage accordingly — annual average alone is insufficient for sizing.
  • A design rainfall event (e.g. 75th percentile annual rainfall) was used for conservative sizing — not the maximum or average.
  • Rainfall data used is at least a 10-year average — shorter records do not capture year-to-year variability.
  • For recharge pit sizing, the 1-hour peak rainfall intensity (mm/hr) for the location was obtained — not the annual total.
✓Runoff and Collection Efficiency+
  • Runoff coefficient was set appropriately for the roof material — RCC terrace 0.85–0.95, clay tile 0.75–0.90, corrugated sheet 0.70–0.90.
  • First-flush diverter volume was calculated and a first-flush device was specified — first 2.5mm of rainfall per 100 m² catchment is diverted.
  • Collection efficiency factor of 0.70–0.85 was applied to account for evaporation, spillage, and first-flush losses.
  • Gutters and downpipes were sized to carry peak rainfall intensity without overflow — undersized gutters lose runoff before it reaches the tank.
  • Leaf guards and mesh filters were specified at all gutter inlets to prevent blockage and debris entry.
✓Storage Tank Sizing+
  • Storage tank volume was sized for the longest dry period in the local rainfall pattern — not the annual total.
  • Daily demand for the intended end use (toilet flushing, irrigation, car washing) was calculated and used as the drawdown rate.
  • Rainwater harvesting is not intended for drinking without treatment — end use was confirmed as non-potable.
  • Overflow from the storage tank was directed to a soak pit or municipal drain — not to a neighbour's property.
  • For groundwater recharge pits, the soil permeability (infiltration rate) was confirmed — clay soil cannot absorb at the required rate.
  • Storage tank is covered, shaded, and constructed of food-grade material if water is used for any human contact purpose.
✓Regulatory and Maintenance+
  • Local municipal or state authority rainwater harvesting bye-law requirements were confirmed — several Indian cities mandate RWH for plots above a minimum size.
  • Recharge pit location is at least 15m from any septic tank or soak pit to prevent groundwater contamination.
  • First-flush diverter was designed to be manually or automatically reset after each rainfall event.
  • Filter media in the recharge pit — gravel, coarse sand, fine sand layers — was specified and maintenance access was provided.
  • Annual cleaning and inspection schedule for gutters, filters, first-flush device, and storage tank was confirmed.
  • Structural adequacy of the terrace for the additional water load during peak rainfall was confirmed with the structural engineer.
Inspection Notes+
Use the latest approved drawings, specifications, and site measurements.
Complete all critical checks before proceeding to the next work stage.
Record deviations and confirm rectification where required.

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