Welcome to the Bunnings Workshop community @comptonkath. It's wonderful to have you join us, and many thanks for your question about installing agi pipe.
One end of your pipe needs to feed into a stormwater pipe, allowing water from the area to flow into the drain. If you don't connect that end to the stormwater, you'll have pooling water in that location. The opposite end, furthest away from the stormwater, requires an end cap.