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| Five percent of the average annual demand can be estimated: | | Five percent of the average annual demand can be estimated: |
| <math>D_{0.05} = P_{d} \times #\times 18.25</math> | | <math>D_{0.05} = P_{d} \times n\times 18.25</math> |
| {{plainlist|Where: | | {{plainlist|Where: |
| *''D<sub>0.05</sub>'' is five percent of the average annual demand (L) | | *''D<sub>0.05</sub>'' is five percent of the average annual demand (L) |
| *''P<sub>d</sub>'' is the daily demand per person (L) | | *''P<sub>d</sub>'' is the daily demand per person (L) |
| *''#'' is the number of occupants}} | | *''n'' is the number of occupants}} |
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| Then the following calculations are based upon two criteria: | | Then the following calculations are based upon two criteria: |
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| When \(Y_{0.05}/D_{0.05}<0.33\), the storage volume required can be estimated: | | When \(Y_{0.05}/D_{0.05}<0.33\), the storage volume required can be estimated: |
| <math>V_{S} = A \times C_{vol,E}\times R_{d} \times e</math> | | <math>V_{S} = A_{c} \times C_{vol,E}\times R_{d} \times e</math> |
| {{plainlist|Where: | | {{plainlist|Where: |
| *''V<sub>S</sub>'' = Storage volume required (L) | | *''V<sub>S</sub>'' is the volume of storage required (L) |
| *''A'' = The catchment area (m<sup>2</sup>) | | *''A<sub>c</sub>'' is the catchment area (m<sup>2</sup>) |
| *''C<sub>vol,E</sub>'' = The design storm runoff coefficient for the catchment | | *''C<sub>vol,E</sub>'' is the design storm runoff coefficient for the catchment |
| *''R<sub>d</sub>'' = The design storm rainfall depth (mm), and | | *''R<sub>d</sub>'' is the design storm rainfall depth (mm), and |
| *''e'' = The efficiency of the pre-storage filter.}} | | *''e'' is the efficiency of the pre-storage filter.}} |
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| *Careful catchment selection means that the runoff coefficient, for a rainstorm event (''C<sub>vol, E</sub>'') should be 0.9 or greater. | | *Careful catchment selection means that the runoff coefficient, for an individual rainstorm event (''C<sub>vol, E</sub>'') should be 0.9 or greater. |
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| Finally, when \(0.33<Y_{0.05}/D_{0.05}<0.7\), the total storage required can be estimated by adding ''Y<sub>0.05</sub>'': | | Finally, when \(0.33<Y_{0.05}/D_{0.05}<0.7\), the total storage required can be estimated by adding ''Y<sub>0.05</sub>'': |