Professional services

Rainwater Harvesting Design in South Africa

Tank sizing, overflow & water balance for rainwater harvesting — WSUD-aligned stormwater outcomes. Delta Hydro Engineers.

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What is rainwater harvesting design?

Rainwater harvesting design sizes collection, storage, treatment, and overflow so sites capture yield without creating new stormwater risks.

Harvesting that respects stormwater performance

Rainwater tanks change peak timing and overflow ethics on small catchments. We reconcile tank sizing with detention or WSUD targets so sustainability credits do not create downstream flooding surprises.

Honest reliability metrics

We present yield vs demand with explicit dry-season behaviour—so clients understand maintenance, first flush, and when municipal backup is still required.

What we typically need from you

Roof areas, materials, and first-flush assumptions; demand profiles for non-potable uses
Tank vendor constraints, overflow levels, and connection to municipal/stormwater networks
Rainfall series or design storm preferences from the sustainability brief
Water quality pathway (non-potable vs potable) and coordination needs with process engineers

Where we add technical depth

Water balance across wet/dry seasons with explicit reliability metrics
Overflow routing that protects downstream properties and erosion-sensitive discharge points
Integration with WSUD and stormwater quantity targets on the same site
Documentation of assumptions for NEMA and municipal reviewers

When do you need this?

Commercial and industrial buildings targeting non-potable supply
Sites where stormwater attenuation must pair with harvesting
Water-sensitive precincts with dual objectives (yield + flood risk)

Our approach

1

Demand & reliability

Define end-use demand and reliability targets.
2

Water balance

Size storage, first-flush, and overflow for agreed storm inputs.
3

Integration

Align overflows with on-site stormwater management and erosion control.

What you'll receive

Harvesting design memo
Water balance tables and figures

Relevant SA standards

Municipal stormwater and SANS water use contexts (as applicable)

Case study

Ask us for anonymised examples relevant to your sector.

FAQ

Potable use?

Potable pathways require water quality treatment design beyond hydrology—coordinate with process specialists.

Overflow flooding risk?

We verify that overflows do not create uncontrolled stormwater risk downstream.

Tank sizing reliability?

Reliability depends on demand profile and rainfall variability—we document assumptions explicitly.

First-flush diversion?

We can specify first-flush volumes and maintenance implications for water quality goals.

Integration with SMPs?

Harvesting is coordinated with stormwater management plans to avoid conflicting controls.

Author

Stephan Dreyer

Areas we serve

We prepare location-specific briefs for major centres across South Africa — see locations.

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