StormFlow Calculator

This refers to the area of the roof from which rainwater is collected. It’s usually the horizontal projection of the roof surface. To find this, measure the length and width of your roof and multiply them together.

This is the region where materials like concrete or asphalt prevent water from penetrating. Measure the length and width of these areas and multiply to get the total area in square metres.

Specify where you plan to install the tank (e.g., in the garden, under a driveway). Consider accessibility for maintenance and the proximity to the area where the stormwater is collected.

This refers to the weight load the tank area is expected to support. This could be pedestrian traffic, vehicles, etc. Estimate based on the heaviest load likely to be encountered (e.g., 3 tonnes for light vehicles).

This is the frequency at which a certain level of rainfall is expected to occur. It’s usually given in years (e.g., a 10-year storm). Local regulations or historical weather data can provide this information.

This is an adjustment factor to account for potential changes in rainfall intensity and patterns due to climate change. Local guidelines or environmental agencies might provide specific percentages to use.

This is the depth at which groundwater is found. It’s important for soakaway design to avoid contamination. This information can often be obtained from local geological surveys or environmental agencies.

This is a measure of how quickly water can soak into the soil. It can be determined through a percolation test or obtained from local soil surveys.

This is the maximum rate at which water can be released from the tank into the drainage system. Local regulations often dictate this to prevent overloading public sewer systems.