Calculation of drawdown rate Qr

Christian, if I understand the question properly, proper sizing of this tank should be based not on LEED compliance data but on meteoroligical data from the area and calculations of how much water will be required for flushing.

Hello Tristan, I don't fully understand your answer. If we want to reuse the stormwater for flushing for example, I understand that we have to take in account the flushing quantity of water expected each day and increase the tank's dimension. Indeed, without this consideration, the storage tank would be always empty because of the necessity to prevent 2 years design storm. But what is the design storm intervall between two events? 24 hours? (I realize that having two 24 hour storms back to back is rare but it could happen). In LEED exemple p97, they use a design storm interval of 3 days and that make no sense for me. You said it is based on meteoroligical data but I don't understand the link. Thanks

Benjamin, I see you're a student, so I'm wondering if your question is hypothetical or about a specific project. The reason I ask is that hypotheticals can sometimes be more confusing than real examples.The point I was making in my earlier post is very basic: LEED doesn't tell you how to size a cistern. You have to work with the meteroology of the site and the credit requirements you are trying to meet. Those constraints will dictate your calculations. And yes, some of those requirements are imposed by LEED. But it's about your choice of how to meet the LEED credit, not LEED telling you how to design your tank.