RCC Recharge Harvesting Pit: Ring Specifications, Filter Layers, and Depth Sizing

A well-specified recharge harvesting pit is genuinely effective infrastructure. Built correctly, it continues feeding water back into the ground for decades with minimal maintenance. Getting there means specifying two things together, not just one. The ring itself is only half the picture. The depth of the stack and the filter media packed around it, both set out clearly in Central Ground Water Board design guidance, are what determine how well the finished structure performs over its working life.

The Ring Itself

Specification	Value
Inner diameter	2500 mm
Height	1000 mm
Wall thickness	200 mm
Concrete grade	M30
Reinforcement	8mm TMT, double-layer mesh
Curing period	7 days
Volumetric capacity per ring	~5,000 litres
Joint detail	Grooved edge for ring-to-ring alignment

The 5,000-litre capacity reflects the ring’s own geometry: a cylinder 2.5 metres across and 1 metre tall works out to almost exactly that volume. The filter media that fills that space once installed is specified separately, and matters just as much to the pit’s long-term performance.

How Many Rings, and How Deep

Central Ground Water Board design guidance for recharge pits generally recommends a width of 2.5 to 3 metres and a depth of roughly 5 to 6 metres where permeable strata sit close to the surface, extending deeper where they don’t. At 2.5 metres diameter, this ring sits comfortably above the typical range, well suited to higher-capacity installations. Five rings stacked reach the 5-metre depth this guidance recommends, with additional rings added as the site’s permeable layer requires.

A recharge well is a related but distinct structure, used where the aquifer sits considerably deeper and built around a storage tank, filter chamber, and a slotted pipe or strainer feeding a bore rather than a stacked ring shaft. Between a recharge pit and a recharge well, BRHCInfra’s Harvesting Ring is purpose-built for the pit: the more common, more site-adaptable of the two for most rooftop and campus-scale installations.

What Fills the Space Around the Rings

The rings hold the shaft open and structurally sound. The graded filter media packed inside and around them is what turns that shaft into a working recharge structure. CGWB’s standard design for Delhi specifies roughly a metre of filter media in three layers: boulders at the bottom, gravel in the middle, and coarse sand on top. Any silt still present in the runoff settles on the accessible top layer, where it’s simple to clean out, keeping the deeper layers working efficiently for longer.

That top sand layer performs best as a second line of defence rather than the only one. A desilting chamber at the inlet keeps the bulk of the silt out before it ever reaches the rings, and the sand layer inside the pit handles whatever gets through regardless. Pairing the two gives the system genuine redundancy and meaningfully extends the interval between maintenance cycles.

Assembling the Stack

The shaft is excavated slightly wider than the ring’s outer diameter to allow working room. The base ring is set first, and each ring above it seats onto the grooved edge of the one below before the surrounding gap is backfilled. The groove keeps the stack aligned and keeps soil from working into the joint from the side, the same function it serves on any precast section that needs to stay structurally continuous once buried.

What BRHCInfra Supplies

We manufacture the Harvesting Ring to this specification across all of our Delhi NCR plants, with the capacity to supply as many rings as a project’s depth requires, backed by the dimensional consistency that comes from factory-controlled casting. Technical drawings are available for design and tender submission.

If you’re planning a recharge harvesting pit and want the ring count worked out for your site’s depth and catchment area, reach out at +91-9999012399 or brhcindia@gmail.com.

Also read:
Harvesting Ring Product Page