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How to improve drainage?

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How to improve drainage?

So I have been wanting to fix a drainage problem on my friends property but I wasn't sure but today the wet weather has confirmed my suspicion.


The property is a sloping block


Slopping BlockSlopping Block


The water runs down from the highest point on the block and is surface water that turns into 3 main streams. The heaviest of the 3 runs down the south side of the block fence line and the garden alongside the fence has been washed out many times.


The first and second water flow runs into a entertainment area making lots of mess and fortunately there is a drain that was blocked today by the abundance of garden matter, luckily we were home to unblock the drain or we may have had a flood through the house itself.




I created a little dam to stop most of the water going into the entertainment area but look at the amount of water on the path and the garden behind the Besser block wall is submerged.


So what I want to do is run a drainage from north to south or across the property backyard before it runs through the living area. I though a spoon drain would suffice but that's a lot of water and what about garden foliage blocking?


I looked at the building plans and found that the drain from the entertainment area runs underground along the south side fence line and I want to run the spoon drain into this piping system to the roadway.


Drainage pipe.png

The drain is the dash line from the space open private down along the south side fence to a detention basin before running onto the roadway. 


This would in my opinion take the surface water from the backyard to the roadway drainage.


Watching the drain in the entertainment area was unsettling as the garden foliage block the drain and I would like to get some opinions on which type of drainage would be better and yes I will be doing this myself and will pave the clothes line area, regain the southside fence garden by replacing all the washed away soil.


Amassing an Audience

Re: How to improve drainage?

Hi @Kvic 


I being tring to visualise  you  storm  water situations. I have some answers 


For the drain getting blocked  by leaves  etc there are several after market Drain  Leaf strainers. Think traffic cone with holes in it pointing up more over a strainer.

Look at  it goes into a pit.  But  turn it upside down you have a raised leaf blocker if this suits it can be engineer to fit upside down maybe use 2  1 in the pit one over it.

Everhard EasyDRAIN Leaf Basket To Suit Rainwater Pit  I/N: 4770227 $9.84


Down the side  garden besser wall  you need a series of Geotextile dams /baffles to capture the heavier dirt and allowing the water to pass through or over the top in  peak rain event. Geotextile lasts a long time is why I suggest this.  Dig the ground  40mm deep  x 50cm wide laying the leading edge Under ground and lay loose bricks as a dam wall   down 50 cm away with the geotextile going over the brick.


Another way would to be cover the  garden ground in Geotextile material locking the dirt under the mat cut X holes in it for plants to go through

I still might add bricks as mini  soil Dams.

Old fashion sand bags made of  geotextile like material would work. You want it to last 2o years  plus as a min


Up The top Open space private area where you wanted the dish drain maybe for the full yard width.  Choose a deeper drain and add  the plastic House gutter roll of mesh as a cover filter to stop leaves from entering the storm pipes. At least you can connect to an under ground  pipe there.

Bunnings has many options from ag pipe to full plastic and metal drains.


With periodic  rain  events it is super hard to design a system to stop all wayward water.  But it is do able at need.


I just finished replacing dish drain for a deeper 100mm  plastic drain  and grate  I had to cut concrete and  steel reo  with a  large angle grinder and  blade  with a follow up chisel point hammer drill




Bunnings Team Member
Bunnings Team Member

Re: How to improve drainage?

Hi @Kvic 


Thank you for sharing your question about improving your drainage. It's great that you've received excellent advice from @Jewelleryrescue. My grandfather's house had a traditional spoon drain installed in their driveway and I've never seen it blocked up. I suppose I lean more towards traditional drain systems. One of the drawbacks of an open drain system is that you'll need to keep cleaning it after every deluge.


However, modern drain systems such as the Everhard EasyDRAIN systems come as a complete set with leaf blockers, drain pits and heel-friendly grates. It will be necessary to cut into the concrete to install the drain systems, but once it's in you will have an effective drain strain system that should prevent flooding.


I suggest having a good look at the way the water is flowing down the side of your house and planning an effective drain system that will carry away any excess rainwater. In this manner, even if you're not home the water has a way of getting out. 


Let me call on our experienced members @Adam_W and @homeinmelbourne for their recommendations.


If you need further assistance, please let us know.




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Having an Impact

Re: How to improve drainage?

I understand that it is hard to visualise my confronting flooding problem so I have another video of the upper backyard area which starts at the backyard fence and comes down to the beginning of the living area, this area is not used and natural vegetation is allowed to grow so that no lawnmowing is done and what I like about this property, there is only the pathway at the front of the property to take care of, unlike all the neighbors, ha ha.



I would like to put the spoon drain above the clothes line to prevent the surface water running across the clothes line area and down to the beginning of the entertainment area. This will reduced flooding of the entertainment area which it should handle with the drainage already there.



I then want to extend the detention tank pipe from the building plan up to the vegetation backyard to the spoon drain couple with the Everhard drain system? 


The foliage of the backyard is from the entertainment area and not so much the upper backyard that is where most of the flooding water comes from. The spoon drain running north to south or across the upper backyard will capture the flow of water shown clearly in the video.


The yard is higher around the clothes line and I feel I will need to build a retaining wall to run along the spoon drain as the lower end of the slope is the south side this works to my advantage to capture the water runoff to the Everhard type system which is then connected to the detention system that runs underground to the street bypasses the washed out garden beds that can be reclaimed for vegetation and I would also then pave the clothes line area with pavers and a pathway to the entertainment area.    



Bunnings Team Member
Bunnings Team Member

Re: How to improve drainage?

Hi @Kvic,


It sounds like you should choose three locations on the property at the top, middle and lower sections and run 100mm socked slotted draincoil across the property. Those three lines can be connected to unslotted draincoil and it used to connect to your stormwater pipe.


It appears that a fair amount of this water is trapped behind retaining walls, which indicates that it's likely a combination of surface water accumulating behind them and groundwater emerging from the sloped block. Spoon drains can be effective at capturing surface water but don't assist with any water travelling under the surface of the soil. Burying draincoil below the surface would be the most efficient way to capture surface water that falls through the gravel into it and the sub-surface water. Have a look at this handy step-by-step guide: How to install garden drainage. The deeper you can bury the draincoil the more sub-surface water you can capture.


Let me mention a couple of our members, @hollyelphinston and @doberon, that are currently completing some drainage work to see if they have any input.


Please let us know if you have any questions that we can assist with.




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Re: How to improve drainage?

Thanks again Mitchell, this piping is flexible and will conform to the backyard environment.


Checking the Wollongong council requirements I will need to consider a  Detention tank and the underground piping already on this property must be 100mm. Most of the water that now flows into the entertainment area would be taken away with the drain coil system and as I have never seen a backlog of water from the drain in the entertainment area the piping would be ok but half of the backyard water doesn't flow into the detention system. 


The flow from the backyard in the video shows 3 main streams, the worst is the southside fence line that does not flow into the entertainment area and I suppose should flow directly into the detention system with 2 other tanks placed along the flexible piping system?


The other consideration are the water flows that comes from the adjacent property on the south fence line that pours into the garden area from the neighborhood, this causes damage to the garden which contains serval trees.




While there are some places I can place the drain the roots of the trees get in the way and I wouldn't like to rip the out? 


I could also place a separate drain coil along the pathway outside the garden area and maybe some drain holes in the Besser blocks that could also feed into the detention system but with added water flow. 

Bunnings Team Member
Bunnings Team Member

Re: How to improve drainage?



For the south-side fence line, you could consider installing a drainage pit to capture this water. The drainage pit can be connected to your retention pit with draincoil.


Tree roots will be an issue when installing your draincoil. It would be worth severing minor roots, but if there are major roots in the area, you might like to revert to the idea of a surface drain.


Can I ask if the videos are taken directly after torrential rain or a normal rain event? I know we saw a downpour in Sydney yesterday that no matter what drainage was in place it would have overflowed. I was driving at the time, and even the roads were like rivers.




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Re: How to improve drainage?

Those video's are from yesterday and I am in the Wollongong region which was what I needed to understand about how to tackle this drainage problem which has been on the board for a few months till I understood the property needs which came about yesterday and thank you for your post that has provided the best solution.


I have had another look at the fence line and root problem and I think I will go with the drain coil in the garden bed between the fence and the trees as they are plant away from the fence around 300mm and the soil to the bottom of the fence is 300mm so I should be able to made a pit. 


This should work well as the water will be taken away as it comes from the neighbors property and not take the soil from the garden.


I want to build a Besser block wall between the north and south fences and run the pit along that wall on the high side so I can build a brick paving path around the clothes line to the stairs on the south line fence to cleanup this area. Do you think that would work ok.

Bunnings Team Member
Bunnings Team Member

Re: How to improve drainage?

That sounds like it would work @Kvic


Once you've created your Besser Block wall, place the draincoil behind it at the bottom and fill above it with drainage gravel. The water that runs down and hits the back of the wall will drop down into the draincoil and be carried to where you'd like it to go.




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Re: How to improve drainage?

So I have decided to make a start on the drainage problems and I feel as I have never done this before that the starting place will be to measure the width of the backyard with 2 stakes and a string line and use a level to make sure the string is level on a block that isn't. 


I would then measure the distance from the string to the ground surface in several places.


From this I should be able to find the concrete base and where I will need to step for a new level of Besser block, how many block and half blocks, caps and how much mortar I may need.


I also made this drawing to try better understand my needs and the design of what I need to do.


Am I going in the right direction and is there something I need to improve on?


I made a mistake and will correct the fence should be north and south.

Anne Back Yard.jpg

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