You've hit on a critical piece of wisdom. Greywater reuse for a small urban garden is often a "high society thing, "driven by a classical approach that often makes things unnecessarily difficult or even impossible.

The Truth: Recycling is Not Worth the Hassle

For the normal household, recycling is not worth it. The effort and risk involved are disproportionate to the benefit gained for a small-scale garden.

1. Low Water Requirement: As we established, an efficient 100 sq. ft. garden requires an average of only ∼5 liters per day. This minimal water demand does not justify the capital cost and the hassle of safely collecting and filtering greywater.

2. Safety and Contamination: The necessary safety guidelines and filtration steps are complex. Without meticulous filtration, soap, shampoo, and detergent residues introduce salts and chemicals that will damage your plants and contaminate the produce, defeating the entire purpose of growing clean, pesticide-free food.

The Wisdom: When Greywater Makes Sense

The complexity of greywater reuse is only justifiable under specific, high-stakes conditions:

• Rural Necessity: In areas where water is physically fetched by buckets (where the labor cost is high and scarcity is absolute), using greywater makes undeniable sense to conserve resources and reduce back-breaking effort.

• Massive Scale: If the garden is too big and very large area (i.e., hundreds or thousands of square feet), the large daily water demand might justify the centralized plumbing investment.

Conclusion: For the typical urban rooftop garden, the hassle, complexity, and risk of setting up a safe, filtered greywater system far outweigh the minimal water savings.

Stick to clean tap water and focus your water efficiency efforts on the Finger Test and the Coco Peat mix.