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How to install garden drainage

Workshop Legend

Difficulty: Beginner


Often the best way to fix a muddy lawn is by installing underground (sub-surface) drainage.


Here’s how to install a concealed drain to prevent water pooling and help keep your lawn lush and healthy.



Step 1

Decide where to put your drain, and then dig your trench. The rule of thumb is that your pipe should have a space equal to its own width on either side, and at least 100mm from its top to the finished level before the turf is replaced. In our case, the trench is about 200mm wide (65mm space + 65mm pipe + 65mm space) and 180mm deep. Use your level to ensure that the trench is falling slightly in the required direction.


1.1 Mark out and dig your trench.png


Step 2

Lay your pipe in the trench, ensuring it is sitting on the trench bottom. Use your level to check that the fall is correct. Cover with gravel to about 20mm below the existing surrounding soil level. The pipe must be run to a suitable point for dispersal (we connected it to an existing sub-surface drain).


2.1 Lay pipe and cover with drainage gravel.png


Step 3

Trim your drainage fabric to suit the width of your trench. Place it on top of the gravel.


Now, fill the remaining 20mm of your trench with coarse sand.



3.1 Lay drainage fabric and cover with coarse sand.png  3.2 Finish your area to turf roll width.png


Step 4

You can now lay your turf on top of the sand. Use your spade to trim the turf. Use excess sand or loose soil from your excavation to fill gaps along the edges and ends.


Walk lightly over the area to ensure that turf is in contact with the sand base, then water well. The first thing you’ll notice is that the water disappears.


4.1 Roll out the turf.png


Step 5

To finish, replace surrounding turf so that your new turf blends seamlessly. Remove a little soil and replace with sand to improve drainage of the whole area.


Keep your turf moist but not wet while it establishes and apply a seaweed tonic every week for the first few weeks to help it establish. As moisture retention will be low above your drainage trench it may need extra watering during dry periods.


5.1 Repair surrounding areas too.png



  • Slotted agricultural drainage pipe, socked (we used 65mm diameter pipe)

  • Non-slotted agricultural drainage pipe of same diameter (for moving collected water to the dispersal or disposal point)

  • Drainage fabric

  • Drainage gravel (we used two bags)

  • Coarse sand (we used one bag)

  • Rolls or slabs of turf to suit.


  • Digging spade (a trenching shovel is handy but not essential)

  • Short to medium-length level

  • Utility knife or heavy-duty scissors

  • Wheelbarrow.


1.1 Mark out and dig your trench.png

2.1 Lay pipe and cover with drainage gravel.png

3.1 Lay drainage fabric and cover with coarse sand.png

3.2 Finish your area to turf roll width.png

4.1 Roll out the turf.png

5.1 Repair surrounding areas too.png

2 Replies
Finding My Feet

Step 3 instructions are missing. Can you tell me what you used to cover the gravel please 

Bunnings Team Member
Bunnings Team Member

Great pickup, @nick626! The remaining height of 20mm is filled with coarse sand. The sand should then sit level with your surrounding soil.


We'll fix that step up.






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