So, thank you everyone for your input so far, I thought I would update you all on the situation. I have decided to try the soakaway as the surface water in the holes above did start to reduce although quite slowly I might add.
So at the weekend I dug this HUGE hole, I'm still hurting. It is 1200mm deep x 1000mm x 1000mm.
This weekend the plan is to install a french drain along the edge of patio as the red line in the image below shows and then into the soakaway (blue) from the centre. Do you think this is the best route to the soakaway? Also any advice on the build of the french drain would be appreciated.
If this fails to work and the clay soil just creates a pond, I will be forced to divert through the inspection chamber of the soil pipe.
Soakaway - there is unfortunately no absolute limit on how much rain can fall and therefore there is no absolute size which will always be big enough to prevent any flooding ever. If you go to a structural engineer, they would be able to give you a size based on standard calculations. However that would also come with the caveat that standard calculations are based on statistical rainfall data and it's still always possible that a "1 in 100 year" rain storm happens two years in a row. So you could take the view that if that's the biggest hole you can dig (well done, by the way, that must have hurt), then that's as realistic a limit as any other.
French drain - be aware that fine silt washes off your garden all the time, so ideally you put a perforated pipe in a trench, cover it with clean pea gravel and then cover the gravel with 'filter fabric' (weed membrane, basically) to stop the gravel and then the pipe becoming choked with silt. In effect, the trench becomes an extension of your soakaway, so water can go into the ground all along the sides, as well as the pipe itself carrying water into the soakaway.
Your drains - if your drain is not a 'combined sewer' then you could be prosecuted for putting rainwater into it, so check it really is taking your surface water before you even consider it. Personally I would strongly recommend you DON'T connect to the drain, even if it is combined. If you do and you get enough rain to overwhelm it (and as I said, that probably will happen at some point), you'll not have a pool of muddy water in your garden, you'll have a pool of mud and sewage. This, by the way, is why you can be prosecuted for putting rainwater into a foul sewer. Everyone else in the street could get sewage in their garden too.
So if your bigger soakaway is still not working, my advice would be to get a digger in and build a REALLY big soakaway - have a look for 'rain crates', for example - in preference to using the drains.
Gardening on the edge of Exmoor, in Devon
“It's still magic even if you know how it's done.”
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So at the weekend I dug this HUGE hole, I'm still hurting. It is 1200mm deep x 1000mm x 1000mm.
This weekend the plan is to install a french drain along the edge of patio as the red line in the image below shows and then into the soakaway (blue) from the centre. Do you think this is the best route to the soakaway? Also any advice on the build of the french drain would be appreciated.
If this fails to work and the clay soil just creates a pond, I will be forced to divert through the inspection chamber of the soil pipe.
Thanks in advance
Soakaway - there is unfortunately no absolute limit on how much rain can fall and therefore there is no absolute size which will always be big enough to prevent any flooding ever. If you go to a structural engineer, they would be able to give you a size based on standard calculations. However that would also come with the caveat that standard calculations are based on statistical rainfall data and it's still always possible that a "1 in 100 year" rain storm happens two years in a row. So you could take the view that if that's the biggest hole you can dig (well done, by the way, that must have hurt), then that's as realistic a limit as any other.
French drain - be aware that fine silt washes off your garden all the time, so ideally you put a perforated pipe in a trench, cover it with clean pea gravel and then cover the gravel with 'filter fabric' (weed membrane, basically) to stop the gravel and then the pipe becoming choked with silt. In effect, the trench becomes an extension of your soakaway, so water can go into the ground all along the sides, as well as the pipe itself carrying water into the soakaway.
Your drains - if your drain is not a 'combined sewer' then you could be prosecuted for putting rainwater into it, so check it really is taking your surface water before you even consider it. Personally I would strongly recommend you DON'T connect to the drain, even if it is combined. If you do and you get enough rain to overwhelm it (and as I said, that probably will happen at some point), you'll not have a pool of muddy water in your garden, you'll have a pool of mud and sewage. This, by the way, is why you can be prosecuted for putting rainwater into a foul sewer. Everyone else in the street could get sewage in their garden too.
So if your bigger soakaway is still not working, my advice would be to get a digger in and build a REALLY big soakaway - have a look for 'rain crates', for example - in preference to using the drains.
“It's still magic even if you know how it's done.”