ONE RAINFALL SEQUENCE. TWO POSSIBILITIES.

What could your rain supply?

Compare storage sizes using daily rainfall and non-potable water demand. Start with the synthetic example or enter your own sequence.

Open study

Your study

Study name Rainfall source / context

Catchment area m², horizontal projectionCollection efficiency %, user assumption

Daily rain deduction mm on each wet dayDefault daily demand L, used by “Set demand”

The deduction is a simplified daily loss—not a calibrated first-flush device or storm model. Both tanks start empty and use the same inputs. Default demand is an unsaved editing convenience, not a study input until applied.

Compare tank capacitiesA Tank A LB Tank B L

Daily sequence

Consecutive days, no missing records. Blank values are errors, not zero rain.

Day	Rain (mm)	Demand (L)	Remove day

Paste rainfall / demand CSV

Header: rain_mm,demand_l. One record per consecutive day, up to 366. This replaces the sequence after confirmation.

Your inputs stay in this tab. Save a study before leaving.

The comparison

Example

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A transparent model, not a forecast

Each day, in this order

Subtract the declared daily rain deduction, stopping at zero.
Multiply by catchment area and collection efficiency. One mm over one m² equals one litre.
Add collected water to the tank; water beyond capacity overflows.
Supply demand from the tank, then carry the remaining water into the next day.

Read the boundary

Rain arrives before demand in this daily model. Real timing, losses, weather and operation can change outcomes. A larger tank cannot create more rain. A short sequence is not long-term reliability.

No drinking-water, plumbing, structural, flood-protection or compliance advice. Verify local requirements and suitable design with qualified people before installation.