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Welcome to the Bunnings Workshop community @Venugopal. It's terrific to have you join us, and many thanks for your question about drainage.
To install a drainage trench, start by planning the route of your trench from the problem area to a suitable drainage point such as a stormwater pit, or lower area in your yard. Ensure the trench will have a consistent fall of at least 1 in 100 (1cm drop per metre) to allow water to flow freely. Mark out the path with spray paint or string, then dig the trench about 150–200mm wide and deep enough to accommodate the pipe, bedding material, and cover. Once dug, add a 50mm layer of coarse gravel to the bottom to help with drainage and stability. Lay geotextile fabric over the gravel so it lines the trench and extends up the sides, preventing soil from clogging the pipe. Place the 90mm perforated PVC pipe, ensuring it maintains the correct slope along the entire run. Connect any fittings as needed, such as elbows or T-junctions. Cover the pipe with more gravel until it’s a few centimetres above the top of the pipe, then fold the excess geotextile fabric over the gravel to fully enclose it. Finally, backfill the rest of the trench with soil or turf to match the surrounding area. Test the system by running water into the inlet to check for proper flow and drainage.
Remember that any connections to stormwater must be completed by a licensed drainage professional.
Here's a helpful guide: How to install garden drainage.
Please let me know if you have any questions.
Mitchell
Any drainage gravel would be suitable, @Venugopal—anything from 8mm to 15mm. If you click the link, you'll be able to check what's available at your local store.
Mitchell
