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Rainwater First Flush Diversion Calculator

Rainwater First Flush Diversion helps you calculate a specific quantity (litres) from values you measure or plan for: Roof collection area m², First flush depth mm. The calculator evaluates the stated equation directly on your device and displays the result without contacting a server. It is designed for the particular task named above, not for automatically estimating all related costs, risks or conditions. Select first-flush depth based on local water quality and equipment. Verify your measurements and compare the worked example before applying the result.

How to use this calculator

  1. Measure or estimate Roof collection area m², First flush depth mm using a consistent set of units.
  2. Enter the values in the labeled input boxes; values outside permitted ranges are rejected.
  3. Read the numerical result in litres; adjust inputs to compare scenarios.

Rainwater First Flush Diversion formula

roof*diversion (litres).

  • The calculation uses the input variables Roof collection area m², First flush depth mm according to the specified expression.
  • Select first-flush depth based on local water quality and equipment.

Worked examples

Worked example: Rainwater First Flush Diversion

Example values: Roof collection area m² = 12, First flush depth mm = 4.

Apply roof*diversion.

For the stated input values, the calculated result is approximately 48 litres. Recheck measurement units and rounding for your real project.

Understanding the result

The result is a quantity in litres, not an independent measurement.

Select first-flush depth based on local water quality and equipment.

Important notes

Select first-flush depth based on local water quality and equipment.

Use measurements from the same scenario and verify local regulations or professional standards where relevant.

Frequently asked questions

What does Rainwater First Flush Diversion compute?

The litres result from Roof collection area m², First flush depth mm using the displayed equation.

Which limitations matter?

Select first-flush depth based on local water quality and equipment.

How can I check the result?

Enter the example values and independently evaluate the formula with the same units.

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Related explanations

Learn the method behind the number or compare the terminology before using the calculator.

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This page provides a calculation tool plus explanatory information so you can understand what the result means and when the underlying method may not fit your situation.