A soakaway system is designed to take away the storm water from your guttering back into the ground. The pit should be atleast 5m away from any foundations and deep enough so the water drains back into the ground. For this build I could have done it in two ways, the first dig a large pit and fill it up with broken clean bricks. The second using plastic Soak-a-away crates which I went for. This was an added £500 expense however due to the amount of water from the main roof and the new roof on the extension I would really need a system that would cope with heavy rain falls, so crates would be the best option.
Looks a bit like the good old milk crates. Based on a simple calculation (i will post this later once i remember!), I required 10 crates or a 4 cubic metre brick filled pit. That’s a lot of bricks and soil to remove. The crates will only require half the amount. 10 light duty crates were delivered with plastic pipes that are used to join and build the soakaway into a larger crate. To prevent any soil spilling into the crates it must be surrounded in suitable fabric. It also needs to be surrounded in pea shingle before it is covered with soil. I choose the center of my lawn approx 6m away from the extension. Two soil pipes would carry the water in. I marked the line using line paint and left the digger to do its work while I made some coffees. Oh bugger, he started digging on the wrong side of the line so the pit turned out 2m longer. No problem as I could fill it up with broken bricks. It’s best to dig the pit before assembling the crates just in case you find the ground is not suitable.
I joined them up in a staggered formation on the ground. I also used some strong wire ties to add extra strength. It will be pretty heavy when lifting into the pit.
I joined them up in a staggered formation on the ground. I also used some strong wire ties to add extra strength. It will be pretty heavy when lifting into the pit, not a one man job. Makes me think if I should have assembled it in the pit. Anyway time to wrap the fabric around the whole thing in 2 layers. Best to lay the fabric on the ground, place the crates on top, wrap all over. I used a standard paper stapler to secure the fabric ends.
I was amazed to find perfectly clean sand below the solid and rocky clay. This is the stuff they wash and sell us in bags! Anyway approx half a ton of shingle was thrown into the pit so the water can disperse better and to level the ground so the soakaway sits nice and firm. It took 2 of us and the digger to slide the soakaway in. Due to the weight I did hear a few cracking sounds when it was lifted, seems like the wire ties were snapping.
The mini digger driver advised to place shovel before taking the picture so building regs could see the depth if later questioned.
Picture from upstairs. I got the mini digger to dig out the channels before leaving site. I had to dig out slightly more to increase the angle so the water would flowfaster into the soakaway. I could have fed the pipe through the top of the soakaway however I decided the keep the pipe as low as possible to prevent a fork cracking the pipe if in future the if the lawn ontop was air-rated. I marked where the pipes would enter. Each crate has a knock-out for the pipes that are off-centee. It’s best to get the crates placed the correct way up before covering.
Run of pipe
I soon worked out thats the pipe would have to enter the soakaway from the top. The angle was too great. I had to 2x 110mm elbows.
I read somewhere that the fall should be 1 in 50. Using a string line and spirt level I got the angle set.
Next I placed the drain with 1 riser surrounded with shingle 2 bricks below the damp proof where the slabs for the pation would sit level. The drain has a intergrated bottle trap to keep any rodents and smells out.