Rainwater Harvesting & Recharge
Retaining rainfall in the aquifer instead of discharging it.
Overview
Roof and paved-area collection, conveyance and recharge structures built under state building bye-laws and municipal water conservation rules. The duty is the opposite of stormwater drainage: the water is held and infiltrated rather than carried away.
Specification
- Product range: Alcorr DWC HDPE (Perforated + Solid)
- Standard: IS 16098 (Part 2)
- Conveyance Sizes: ID 100 mm to ID 400 mm
- Recharge Sizes: ID 150 mm to ID 600 mm
- Standard Code: IS 16098 (Part 2)
Why HDPE here
- Perforated sections infiltrate along the whole run, not just at a pit
- Inert material does not leach into the water it returns to the aquifer
- Light enough to install inside a finished plot without heavy plant
Typical deployments
- Rooftop collection down-takes
- Recharge trench and pit liners
- Percolation galleries under paving
- Storage tank inlet and overflow
Specification and site notes
First flush before anything else
The opening minutes of a storm carry the roof's accumulated dust, bird droppings and leaf litter. A first-flush diverter that discards that volume is what keeps the recharge structure from silting up, and it is the component most often value-engineered out and most often the reason a system stops working.
Percolation rate sets the geometry
The recharge structure is sized by the soil's infiltration rate against the design storm, not by roof area alone. Run a percolation test on the plot first. In low-permeability soil a trench with a long perforated run outperforms a deep pit, because infiltration happens over the whole wall area.
Perforated in the gallery, solid on the way there
The conveyance run from the down-take to the structure is solid-wall so nothing is lost or picked up en route. Only the run inside the recharge trench or gallery is perforated. Wrap that section in geotextile within a graded aggregate surround, or the slots blind with fines in a season or two.
Keep it serviceable
Bring a silt trap and an inspection chamber to the surface ahead of the recharge structure and record where they are. A recharge system nobody can desilt is a system that quietly stops recharging, usually without anyone noticing until the borewell yield falls.
FAQ
How is rainwater harvesting piping different from stormwater drainage?
The duty is reversed. A storm drain carries water off the site as fast as it can; a recharge system holds it and infiltrates it into the ground. That changes the design: perforated pipe in a granular surround inside the structure, a silt trap and first-flush diverter ahead of it, and geometry set by the soil's percolation rate rather than by peak discharge.
What sizes are used for a recharge system?
ID 100 mm to ID 200 mm for roof down-takes and conveyance on a plot; ID 150 mm to ID 600 mm perforated for recharge trenches and percolation galleries on campus and township schemes.
Does the whole run need to be perforated?
No. The conveyance from the down-take to the structure is solid-wall, so nothing is lost or picked up en route. Only the run inside the recharge trench or gallery is perforated, and it should be wrapped in geotextile within a graded aggregate surround.
Why do recharge structures stop working?
Silt. Either the first-flush diverter was omitted and the roof's accumulated debris went straight in, or the perforations blinded because there was no geotextile envelope, or the silt trap was never desilted. All three are avoidable at design stage and expensive to fix afterwards.
Commonly specified sizes
Related applications
See also
For CAD drawings, compliance certificates and B2B pricing estimates, contact mktg@alom.in.
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