ONE ENTERED EVENT. A CLEAR WATER BALANCE.

How much rain
could you collect?

Turn your entered rainfall and connected horizontal catchment area into a volume. Keep percentage capture losses, a separate event loss and free storage capacity apart.

No forecast or location lookupLitres and explicit gallon units

Describe the rainfall event

Defaults are illustrative arithmetic, not measured rain, a forecast or recommended system settings.

Rainfall and connected catchment

Entered rainfall depth

Total depth for your chosen event, not mm/hour.

Rainfall unit

Horizontal connected catchment area

Plan-view footprint draining to this collection point. Exclude unconnected sections; do not use sloping surface area.

Area unit

Keep the two loss assumptions separate

Capture fraction before separate loss · %

Your assumed fraction reaching the separate-loss stage. Exclude the fixed loss entered below to avoid counting it twice.

Loss, storage and result unit

Separate event loss / diversion

A volume deducted after the fraction, at most the water then available. Enter 0 if already included in your fraction.

Optional storage comparison Compare with entered free storage capacity

Free capacity available before this event

Unused space you supply, not the tank’s total rated capacity. No water use during the event is modelled.

Turn off if free capacity is unknown. Retained volume and excess then stay unavailable.

MODELLED COLLECTION AFTER LOSSES

Check the inputs.

No usable water balance is shown until active inputs are valid.

Gross rain over entered area
Not captured under your fraction
After fraction, before separate loss
Separate loss actually deducted

Against supplied free capacity

Entered free capacity
Retained within that headroom
Excess over that headroom

Where the gross volume goes

Mutually exclusive volume parts under your entered assumptions.
Not captured under fraction
Separate event loss
Collection after losses
Retained against headroom
Excess over headroom

Show decimal volume record

An entered-event volume balance. No actual tank level, rainfall timing, inlet flow limit or simultaneous use is predicted.

Selectable rainwater event report

01 · THE AREA

Count the connected footprint

A sloping roof has more surface than its horizontal footprint. Use the connected area seen from above for this rainfall-depth model.

02 · THE LOSSES

Deduct each assumption once

The percentage describes capture before a separate fixed event loss. If that loss is already in the percentage, leave its volume at zero.

03 · THE STORAGE

Compare with known headroom

Free capacity is an input, not a measurement made by this page. Read the worked water balances and limits.