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After having the gutters replaced, I noticed in the next downpour there didn't seem to be a lot of water coming out of the stormwater pipe at the gutter. I pushed the hose up the pipe by only 3ish meters before it would go no more. I then tried to put the hose an full bore and see what happened to the water. I had water coming out of the downpipes and around the yard even. In the downpour I noticed the water running along underneath the house along the edges of the brickwork/foundation. This is the First stage of rectifying it. Not as hard as it looks technically, just a lot of physical work was involved.
Materials
100mm * 6m PVC PVC DWV pipe 6 of
Various fittings and bends plus y joins.
Water Pit 3 of
Aluminium water pit grate 3 of
Stainless steel screews self tapping 25mm
Tools
Shovel
Crowbar (6 foot)
Mattock
Wheelbarrow
Containers to carry soil
Steps
Step 1
I had the plumber come out to see if the stormwater pipe could be cleaned out of chased. No to both answers even after digging a hole to see down the existing stormwater pipe. To fix the issues I could run a pipe alongside the house and attach it to the wall and then join into the stormwater pipe in the ground or I could put a new pipe in. I chose the later as I thought the first would detract from the look and also potentially be knocked/broken by pushbikes/wheelbarrows ect in the future.
This was the first indication of stormwater not going where it should be. I just had the sewage issue sorted and then more water under the house.
The Stormwater outlet is directly in line with me in the gutter. I could only chase the pipe this far up the hill with the hose and then it would go no further.
When I put the hose down the downpipe at the back of the house to charge the pipe so i could see if there was water going anywhere this happened.... The Water came straight out of the bottom. You can see the dodgy brothers work with the PVC pipe just under the concrete path...
This was my main concern, when it poured rain I could hear and see water gurgling through the brick wall. I figured that water was running down the path and then coming through the cracks in the brick work... Turned out to be partially true.
Water leaking out from the point near the downpipe. I couldn't understand why at first.
After breaking the concrete that concealed the bottom of the downpipe I started to have an inkling why water was coming out...
I had the plumber come back with his camera at this point to see what state the pipes were in. He could only get the camera further 2m down the pipe. The pipe was blocked / filled with silt/something.
Step 2
I had made the decision to replace the existing pipe and figured the easiest way would be to dig up the old pipe and follow the same course it took. Stormwater pipes need only a small fall to be ok I was told but I wanted to "do it properly" in my mind so the old one was coming out.
This part of the replacement project only goes from the gate (At the left corner of the brick wall) to the back of the house. I was hoping that the stormwater pipe could be "cleaned out" tho not really believing it.
Starting to break up the concrete and figuring that the pipe would be under the thin sided section of concrete path...
I had a LOT of concrete to break up. I used a sledge hammer and a 6 foot crowbar to break it all up.
Really thought I would find the pipe underneath the dirt of the section I had smashed through. It made sense to me if I was putting in a pipe Id do it that way...
Digging down to find the pipe. I just kept on digging and getting further towards the fenceline.
Was shocked to see how far over the stormwater pipe was, was also shocked to see how the downpipe joined a terracotta pipe that joined an old pvc pipe. The old PVC pipe was 90mm and very thin walled. There was no jointing glue anywhere.
The middle downpipe... if you look straight up from the downpipe there is another stormwater pipe that has been "jiggled" into the terracotta pipe... It all crumbled in my hands when I was unearthing it.
The rear of the house downpipe... So shallow you could walk on the pipe directly.
Slowly working my way back down the path after realising that the old pipe went up the center of the path.
Sketch of what I was thinking I should do to rectify the water issues.
Step 3
Once the concrete had been removed then I wanted to follow the old pipes route. Looking back at the project I really could have left the old pipe in situ and dug a shallower trench and put a new pipe in. The fall I ended up having was a decent one so shouldn't have any problems.
One of the piles of broken pathway that would be reused later for building Gabion walls.
Uncovering the old pipe. I did hit it with the crowbar a few times but as I was ripping it out I wasn't too fussed. The pipe was squashed flat in several places from clay movement compacting the pipe.
The pipe was full of dirt that had built up from the pipe squashing. There was only clay around the pipe. Digging through the clay could only be done with a crowbar.
Halfway up the hill.
Old pipe gone and trench cleaned out.
Rain collection Pit in place to see how it would sit. I wanted to have an air gap at the bottom of the downpipe to allow leaves to be blown away.
A downpour showed me where the water was going... Also silted up my trench again. The water ran nicely down the slope.
Large roots from next doors gum tree were saying howdy to my old pipes... Dodgy brothers handiwork can be seen in how the old stormwater pipe ran.
Placement of pit to see how it would sit. The rest of the path is for another project.
Step 4
This stage I started putting in new piping. I went with 100mm PVC pipe that was for sewage. I wanted the wall strength to be stronger then a stormwater pipes strength. Lucky I had bought the pipes before the price rise through covid. I had bought 6 of 6m lengths for a 30m ish run all up.
^ pipes, had a mate help me out with delivery.
8mm gravel for going around the pipe and for it to sit on. This will should stop the compaction of the pipe and also allow free drainage down the hill. This will also funnel the water away from the brick wall.
The pipes being set out to see how I would connect them together. I have an inspection point at the top of the run that isn't glued. This is for future expansion or continuation if needed.
The pipe will be laid over so the vertical bits will be flat on the ground.
PVC glue, don't get this on yourself .... yes I did,.... Also yes I have used this all my life lol
To show the angle from the collection pit.
the pipe that is standing up to the bottom left is the inspection point and also will allow to blow out any leaves/dirt that gets stuck in the pipe.
Inspection point.
Backfilling the trench with 8mm gravel (I purchased 5 and a half ton. My calculations where a little off I ordered twice as much as needed for the trench.... but ended up using it all.
Made sure I covered the pipe by an inch at least.
All filled in. Now for backfilling with clay and overtopping to allow for settling.
Half way point of the stormwater repair
Backfilled and overtopped with clay that I had dug up. I didn't place anything between the gravel and clay as didn't think it was necessary and really just wanted it done. I let this settle for a few months before I started work on the pathway itself. Project to follow.
Hi @Dave-1
Thanks for the update, will you be laying down new pipework near the old earthen works set? Looking at the photo, I don't think its worth digging out. I suggest digging a new channel beside it and putting in new PVC pipes.
Please keep us updated with your progress, we look forward to seeing your drainage repaired.
Eric
Good Morning @EricL
I actually dug the old one out, I wasnt sure where it ran so figured I could just follow it and then replace it. I Had never done any stormwater rectification before so I wasnt confident. Looking back I could have saved so much effort by putting a new one in at a shallower depth. "Shrug" Live and learn but this piping drains very nicely now 
I Will try and post stage 2 later today. One thing doing the extensive works was it showed me how water runs down the block. I am not just talking about surface water but subsurface water. With the gravel around the stormwater pipe it really acts to drain the surrounding earth. It might sound boring but I actually have found it pretty interesting. I think I have a few photos that will show what I am talking about.
Dave
