Any Advice would be appreciated I had a soak away in my garden for years which seemed to handle the water from my main roof fine,but to be honest I only had a small pathway surrounded by lawn so I never checked if it was soaking away fully nor did I notice any real problems with excess water, I did notice a couple of times in many years after a extremely heavy rainfall the path would be under water but it went as soon as the rain stopped.
Last year I had a kitchen extension,and then got my rear garden around the extension paved, right the way across my house with oak sleepers acting as a retaining wall, the old clay soak aways were dug up and replaced, they were as expected silted up and full of roots.
The guy doing the work put new plastic pipes in, went out 5 metres from the house,dug 2 pits 1.5m x 1m the new pipes went into them and he put shingle around them, the building inspector came and said the was OK and he filled them in.
The soil where I live is very sandy and even when digging the footings for the extension we only had to go down barely 1m as we had hit hard pack LIKE DIGGING ON A BEACH.
Well since then we have had terrible weather but the soakaways have been backing up flooding the patio to an inch deep again it drains away quite quickly mainly through the slabs.
Any way I had the guy back he dug them both out the water was very stagnant he went down a bit deeper and put an elbow on the end of the pipe doing down, he did a water test which soaked away and filled both pits back in.
Well more rain last night and on checking the drains X3 of them the water was again backing up or overflowing over the plastic grid onto the patio. image
My initial thoughts looking at your picture is that the soakaway isnt large enough to hold a good volume of water. Is it getting overcome by heavy rainfall? Probably.
For my money i would dig 1200x1200x1200 and put crates in there
Yes I would have gone with crates, but the natural land drainage has never been a problem where I live, ive never seen a puddle on my lawn or had a problem like this before like mentioned the old clay pipes seemed to handle it OK before and the extension was on 4m x 5m.
I initially thought the guy who dug the two pits out didn't put enough pea shingle around them,I thought that the pits had to be half filled with shingle then back filled in, the shingle would act like a crate spreading the water out, the only thing the building inspector asked the guy to do was go a bit deeper which he did, the pits were about a metre square and 1.5m deep.
any other ideas ?
Well that picture shows what i would consider 1/4 of the size needed.
I cant give any other advice than what i would do if i had the problems you are having. If its overwhelmed then its too small. Others may have a different view yet.
why is he filling the pits with shingle?
is that what the BCO asked for?
always used to be hardcore ===> plenty of voids
filling it with shingle you are taking the storm surge capacity away
I would go for crates encapsulated in terram or similar non woven geo textile
LLL
Another issue is that the pipe is at the bottom of the hole and not near the top meaning the water can only fill a small area before it backs up you need to go much much deeper with it.
That is the pipe after its been recently re excavated last weekend,so the original pit when it was put in a few months ago was deeper below the pipe by 300ml+.
Im gonna dig it back out and put in 2 crates in each pit as it describes within this web site.
I only wished ( I did have the thought but I was away when the guys dug it out last weekend) to tell them to leave it open would have saved me some elbow grease.
Thanks for all your help
Honestly to get a decent depth under that pipe is a job for a digger you'll need to go down at least another 1.2m making the hole over 2m deep you could get killed if the sides went. As for crates you'll need a least 6 of them. Can the pipe not be raised.
as long as there is a large slope on the pipe it does matter how low down it enters the pit the water will find it own level filling the pit first, before the pipe.
however, Pablo is right about you being in a hole that is to deep, if it is soft like you say the sides could go in, especially with all the rain currently.
The problem I have is my garden goes uphill so without digging up the patio I cant raise the pipe, where the patio is and where the water comes out of the plastic grids its like a sunken patio, the pipes running from them were at a slight slope and the hole was originally deeper and was OKed by the principle Building inspector ?
We have had extreme weather conditions and as said before ive never even seen a puddle in my garden the natural drainage is normally excellent as its so sandy no clay at all.
But this is something I want to try and get right I think how ever well it could have been done,No one could have foreseen how much rain we would have had this year.
Ok I have the guy coming in Monday to re excavate the holes,making them go deeper, Im going to get x 5 polystorm crates three for one pit which takes most of the rain and two for the other that is only taking the rain from garage and small roof area.
Can i get rid of some of the old material I have laying around ?
I have loads of old engineering bricks and about a ton + of mixed sand, building sand and ballast can i use this to fill in bottom of the pit then put crates on top wrapped in geotextile and then put ballast around it then back fill with soil would this work OK.
If you break up the bricks you could use them as side-fill, mixed in with the gravel you should use, and sprinkle the odd bit of sand in, too. You could use the sand/ballast as a base, but you need to be sure to keep the building sand to a minimum as its finer grain size and higher clay content can cause problems if used in large clumps.
