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How to add garden drainage?

I have a pool fenced garden, approx. 1.8m x 3.6m at the back right corner of my house. The area faces south east, with the long boundary to the south. There is no drainage and when following any substantial rainfall the area stays wet/damp for several days.

During Autumn and Winter the area does not get much sunshine, in Spring it is in partial shade, but in Summer it gets a few hours of full sunshine.

I would appreciate any suggestions regarding draining the area and suitable plants for low maintenance.

Viewed from EastViewed from South

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Comments

EricL

Hello @dgb278

Thanks for sharing your question about your garden. For your garden, there are two main aspects to consider: drainage and plant selection.

For drainage, since the area holds water for several days after rain, you will want to improve how excess water moves away. The simplest option is to create a shallow French drain. This involves digging a narrow trench, lining it with geotextile fabric, adding a layer of gravel, then laying in a slotted agi-pipe that carries water away to a lower point in your yard or a stormwater connection. Once the pipe is in, you cover it with more gravel and soil. If connecting to stormwater is not practical, even just a gravel-filled soakage trench can help water dissipate more quickly.

Another option is to slightly raise the soil level in the garden bed by adding free-draining mix or organic matter so the root zones of your plants sit above the wettest layer. Please remember that connecting your agi-pipe to the storm water will require the services of a plumber so that it is joined safely and is compliant with plumbing rules and regulations.

For plant selection, you will need species that tolerate periods of damp soil but also partial shade for much of the year, with some direct summer sun. Native options include lomandra, dianella, swamp banksia (Banksia robur), and native iris (Patersonia). These are hardy, low-maintenance, and handle wet conditions well. If you prefer exotics, clivias, hydrangeas, ligularia, hostas, and Japanese iris are good candidates. For a splash of colour, impatiens and coleus do well in semi-shade. Grasses like carex or liriope also cope well and provide structure with minimal upkeep.

Let me call on our experienced members @Noelle and @mich1972 for their recommendations.

If you need further assistance, please let us know.

Eric

dgb278

https://www.workshop.bunnings.com.au/discussion/comment/57418#Comment_57418

Hello Eric. Thanks for your quick reply and very helpful suggestions. Unfortunately the block my house is on does not have in-ground drainage. The only storm-water drainage is off the roof via the roof gutter and in-ground pvc pipe to a kerb-side drain at the front of my home. My block slopes slightly from front to back, so I will put a drain across the widest part of the garden to a "T" piece, then run it at 90 degrees to the south. I will also run an ag-pipe from under the house on the south-east corner to join up with the third part of the "T" piece. What size agi-pipe do you suggest? Would 65mm diam. be enough or should I opt for the 100mm?

My wife will enjoy buying a range of your plant suggestions from Bunnings and planting them.

MitchellMc

https://www.workshop.bunnings.com.au/discussion/comment/91033#Comment_91033

Hi @dgb278,

For your garden drainage, it’s generally true that bigger pipes are better because they handle more water and are less likely to clog. That said, for the area you’ve shown, a 65mm ag-pipe will probably go a long way toward resolving the issue, especially if it’s installed with a good fall to the outlet. You could also take a phased approach: install the 65mm pipe now and then, over the next couple of years, gradually build up the soil in that area. This will help raise your plants slightly above the surrounding ground, giving their roots a better chance to stay out of constantly damp soil while the drainage settles in. It’s a practical balance between cost, effort, and functionality, and should work well for the plants.

Please let me know if you have any questions.

Mitchell

dgb278

https://www.workshop.bunnings.com.au/discussion/comment/111472#Comment_111472

Thanks Mitchell. The 65mm seems to be the way to go then.

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