# Forum Home Renovation Landscaping, Gardening & Outdoors  Need Help with yard drainage  - to save Pool a 2nd Time.

## Jdubz

Hi there! Any help is much appreciated.  
Just bought a place and with torrential rain coming weeks after I moved in (April 2022) - I quickly realized Drainage in the yard was completely not working and to make matters worse - the surface water eventually ran under the pool - lifting the floor so much it cracked it! Big bill later to repair pool - will be finished soon - meanwhile looking to comprehensively ensure water moves as fast as possible off the yard.   
Yard is heavy clay based basin - very little fall - about 1/200 from back fence to back of house, 20m. Then slightly better from house to the street. Thankfully I have two serviceable stormwater drains, one on either side of the house. 1 x 100mm that runs under concrete the whole way from back of house to street. The other 90mm runs under concrete from front of house to street.  
Picture insert is to scale. 2 squares = 1m. Light grey is concrete slabs, black is interior fencing - and dark red is brick bordering.  Actually photos - attached at the bottom of post.   
Without dwelling on the past mistakes of the system that was placed in there originally - (all slotted 90mm or 65mm PVC no fabric sitting in 10mm gravel drains) - with bottomless concrete pits collecting surface water - My guess is must be 30yr+ old - at least they knew they had an issue - and I'm sure it worked at some point . All these pipes now, from behind the house, in the yard - are 90% full of clay, dirt and palm tree roots, the gravel drains are blocked with clay. Image below - 
Green Squares are concrete Pits - Green lines are Gravel drains with slotted PVC. There are downpipes on all roofs for what it's worth.    
With 20mm of rain - the yard can fill up in many places. Some water sheds coming from neighbour left of image - and a pool of water under fence with back neighbor. Image below dots out the pooling on the yard and it's severity. Notice, the yard is not flat flat, but has not great fall. Within the yard there is built up areas, mainly away from the house and pool, and two very low lying areas - directly in front of shed 2 and between shed 1 and concrete slab.    
What to do?! I know I must replace all the current drainage. So the plan is work with existing layout - digout all all gravel trenches, remove pipes and concrete pits - and update with current standards for Gravel drains - adding GEO fabric - using 100mm Ag pipe and larger 20mm+ gravel rock for a quicker flow. Considering adding the extra 100mm PVC pipe in trench as well  just to concentrate on low areas with surface drains and collecting the run off from all backyard roofing - rather than overwhelming the gravel drain.  
The catch 22 is of course - there's barely any fall - so removing gravel drains and replacing everything - has left me with no where to go in fall so I can't connect to the 100mm stormwater drain with fall - that's again fixed in to concrete at back of house - inside a garden bed of all things - and connected to a T -junction from a downpipe.   
This has left me to decide that perhaps adding a 40L pit and sump pump will help me to create the fake fall in the trenches I need to move the water away - alas - there's no other way around it I see. 
The two areas to place the pit, that I see are ideal,  would either be - as close to the 100mm outlet as possible - but then I'm diverting all water closer to the house - or placing the pit at the lowest point in the yard and pumping it out - this means digging in extended underground cable - and pumping 15m+ in to 100mm pipe. At least with it close to the house - The pressure coming out of 40mm or 50mm PVC in to 100mm from close distance will give it some run to the street.  
Below is the 1 stage DRAFT outline of the pits and pipes I've mentioned, pretty well mirroring the current layout with improved pipe system and better sediment control.   
Does anyone have any thoughts on if I'm on the right track - or perhaps there's something Im not seeing that could spell furter trouble. Any help is much appreciated!

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## droog

Maryborough where ? I am guessing QLD 
A pumped solution is a solution waiting to fail and blackouts often occur during storms. Been there done that.
A 40l pit will fill in no time in heavy rain a larger volume is needed even if it is a low area in the yard that can fill during heavy downpours and drain with time. 
Where does the point of discharge go to ? Out to the gutter or to council drains ?

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## Jdubz

Hi Droog, thanks for your reply!  yes, Maryborough QLD. Thankfully not in any flood zone.  I'm acutely aware of Murphy's Law, but in saying that - I honestly can recall only 2 blackouts in the last 5 years - none in response to weather. I would like a plan B if the pump fails - but absolutely am interested in if there's another way - without this. 
40L pit would only house the Pump - which on paper can pump 125L/Min. Though - I might have to get a deeper pit to increase the fall.   
The 100mm discharge is sent out in to the gutter , the 90mm, on to the grass - a foot from the gutter < not ideal > so looking at extending this in to the gutter.

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