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Topic: Soakaways in clay soil, ...they don't work< Next Oldest | Next Newest >
Tony McC
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Posted: 09 July 2006,17:55 QUOTE

After every downpour, I get an email or ten along the lines of...

"My garden is flooded, so I dug a soakaway and the water hasn't gone. Help"

The problem is that it's not a soakaway that has been dug: it's a hole. The difference between a soakaway and a hole is that a soakaway enables water to soak away, hence the name, whereas a hole is just a missing bit of ground. If you dig a hole in the clay, to where will the water soak away? Exactly! It won't which is why it is referred to as a hole.

If you want to know what makes an excavation qualify as a soakaway, read this page on the main website.


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salvador
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Posted: 15 July 2006,21:46 QUOTE

Top class post. :)
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earthwagon
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Posted: 04 Aug. 2006,10:24 QUOTE

Tony

Apologies in advance - you must be sick to death of posts containing the words "drainage" and "clay".  But here goes: I haven't laid my patio yet but I'm already having nightmares about the big flood.  My problem is that the ground, which is heavy clay, also slopes upwards away from the back of the house.  The site's about 5m across and I've excavated it level, so the depth at the far side is about 70cm below the surrounding area.

The theory is that the patio should have a fall away from the house.  However, the only existing drain point is located in the side passageway adjacent to the house wall, which is considerably higher than what will be the natural accumulation point for stormwater, so I can't lay a pipe to it.  Given that a soakaway won't work and SUDS (which I'd like to do) probably won't work either, what can I do?  Installing a complete new drainage pipe all the way out to the front of the house is out of the question.  Even breaking the rules and having a fall towards the house would not work if I lay the patio two bricks below the existing DPC because the side passageway is only one brick below DPC.  The house is circa 1928.

Should I break two rules and (a) lay the patio with a fall towards the house and (b) lay it higher so as to meet the side path as well, and then use a dished channel to direct the water?  The only alternative I can think of is installing a water collection tank below the excavated level at the far side and using an automatic electric pump to bring it up into a water butt.  Any comments would be gratefully received, thanks in advance.  ???
Sad diagram, plan view, not to scale!:

Far side, 70cm lower
than side path
-----------------------
\                           | Party
|                           | wall
|    Patio               |
| approx 25 sq m  |
|                          |
|<-conservatory  |
|                          |
---------------        |
House         |       |
                   |Side|
                   |path|
                   |      |
                   |      |
                   o Drain
                   | Gulley
                   |      |
                   |      |
---------------       |
                          |
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GB_Groundworks
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Posted: 11 Aug. 2008,21:20 QUOTE

i just lost a job for a septic tank install because after doing a soil porosity test (2 hours to drain 150mm), and explaining that it was heavy clay and wouldn't drain properly with a soakaway and that in my opinion the best way to go was a 300m+ drain field using the klargester easy drain.

so i was alot more expensive than a guy who told the client that a large hole back filled with hardcore would work. i pointed the client to this site to have a read but never heard back.

he'll have a nice bog in his padock soon.


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lutonlagerlout
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Posted: 11 Aug. 2008,23:04 QUOTE

water does go into certain type of clay eventually ,just not as quick as sand or chalk,cant keep overloading victorian sewer systems .
the best one i ever saw was a  fella who decided to connect all his kitchen waste up to the RWP,every time his missus did the washing  a square metre of the garden foamed up lovely,and he couldnt understand it ???
LLL


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henpecked
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Posted: 03 May 2009,20:14 QUOTE

Quote (Tony McC @ 09 July 2006,17:55)
After every downpour, I get an email or ten along the lines of...

"My garden is flooded, so I dug a soakaway and the water hasn't gone. Help"

The problem is that it's not a soakaway that has been dug: it's a hole. The difference between a soakaway and a hole is that a soakaway enables water to soak away, hence the name, whereas a hole is just a missing bit of ground. If you dig a hole in the clay, to where will the water soak away? Exactly! It won't which is why it is referred to as a hole.

If you want to know what makes an excavation qualify as a soakaway, read this page on the main website.

That made me chortle :D  :D  :D
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seanandruby
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Posted: 03 May 2010,21:44 QUOTE

Happy birthday to this post  :laugh:

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rab1
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Posted: 04 May 2010,18:29 QUOTE

belive i once read that on the main site boss :D  :D

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Forestboy1978
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Posted: 17 Feb. 2012,23:54 QUOTE

Only last month I was asked to dig a herringbone drain system leading to a big hole 5x5x5ft in the clay and filled with gravel. I was specifically asked to do this! I queried it wondering where the water was going to go after it goes into the hole, it being lined with clay an all. The project managers words were "they just work"

It got me thinking. I thought well maybe it will work maybe it wont. If it doesn't it's cos it will fill up and be totally useless. If it does it will be because the water will eventually drain through the clay faster than it fills and this big hole filled with aggregate is buying you about a 1 ton water buffer. Perpetual heavy rain would test it but perpetual rain will test anything.

So it comes down to cost effectiveness. Yes the hole in the clay is far from perfect but how often does a garden have to dispose of more than a ton of water very quickly. Surely not very often  or am I wrong!

Of course a stage above this would be to fit one of those crate things instead of aggregate to increase the volume to maybe 2 or 3 tons without doing the maths but from the point of view that infrequent flooding, hopefully after installing this, very infrequent flooding to a garden where this would be nothing more than an inconvenience as opposed to death of plants or expensive damage, it gets the job done right?
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Pablo
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Posted: 18 Feb. 2012,00:08 QUOTE

tbh it's not just the hole thats the problem it's getting the water into the network of drains a clay garden will never be any good unless there is a blanket drain or deep topsoil. If you've dug it at this time of year the chances are you've damaged the soil even more meaning the water will find it even harder to get away.

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Forestboy1978
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Posted: 18 Feb. 2012,00:17 QUOTE

The garden was totally overgrown. It had 20 tons taken out of it by myself including the top soil in the area with bad drainage. The levels were to high to begin with and had to drop to keep things below dpc. The company that designed the garden and were building it were about to put a patio on the poor drainage area and asked us to do what I described. They directed it. I don't have much knowledge on drainage and just did what I was told. I wonder under these circumstances it would be acceptable!
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Pablo
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Posted: 18 Feb. 2012,00:25 QUOTE

did the topsoil get stripped and replaced after the clay was removed to reduce the levels or was it just dug down to suit.

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Forestboy1978
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Posted: 18 Feb. 2012,00:36 QUOTE

I don't know I was off site after that. But I think not. I did the clearance, fencing, driveway, concrete bases and was then asked back for drainage.

They decided to pay ALOT more money for a multi award winning company to build the rest and charge ridiculous prices. I met the guys when I did the drainage and liked them and it did look tidy but they hated the company and did precisely what the designer asked even if they knew it was wrong. They also cut far more corners than we dare do! Cos we liked them and we had a few days off we came in and gave them a hand to see how they do things and it gave us a real confidence boost to be honest!
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Forestboy1978
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Posted: 18 Feb. 2012,00:59 QUOTE

No sorry of course I know. It was stripped down to suit there was to be minimal replacement around the borders where plants were to be planted and 3 meter diameter circle at I guess approx 4" for circular turf!
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lutonlagerlout
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Posted: 18 Feb. 2012,08:58 QUOTE

the latest craic in luton from his holiness the chief BCO is that you shall have 4 aquacells for every 16m2 of roof or drive
he must have shares in that company
when i pointed out that our 3 M3 hole had 300mm of water in it i was told "just do it"
I think the water just fills up to topsoil level then filters through the topsoil
waste of time
LLL
ps and money


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Forestboy1978
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Posted: 18 Feb. 2012,12:32 QUOTE

4 aquacells per 16m2 sounds like an outrageous amount. That works out in the thousands for even an average size drive way!
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msh paving
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Posted: 18 Feb. 2012,15:15 QUOTE

Quote (lutonlagerlout @ 18 Feb. 2012,07:58)
the latest craic in luton from his holiness the chief BCO is that you shall have 4 aquacells for every 16m2 of roof or drive
he must have shares in that company
when i pointed out that our 3 M3 hole had 300mm of water in it i was told "just do it"
I think the water just fills up to topsoil level then filters through the topsoil
waste of time
LLL
ps and money

i think he has very little to say about that, he is not qualified to design a soakaway, its down to structral engineer to state that after a perculation test,
We still use clean rubble round hear have done for years, odd time we need crates but vary rare  MSH :)


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lutonlagerlout
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Posted: 18 Feb. 2012,16:56 QUOTE

they can and do enforce it mark
i have tried the "we have used rubble for years" but they are adamant 16m2  = 4 aqua cells,mainly for roofs
problem is ,its part of the inspection so theres no getting away from it,you do it or the job fails
LLL


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msh paving
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Posted: 18 Feb. 2012,18:49 QUOTE

I'v e one to do in a couple off weeks ,ill need aprox 10 cells on that calc. phew... good job its dayworkish.... :)

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lutonlagerlout
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Posted: 18 Feb. 2012,19:46 QUOTE

thing is building regs  should be exactly the same in kings lynn ,bolton,luton and gatwick
but each and every department interpret it in their own way
I have to say on the whole the BCO in luton are hard but fair,and i dont mind doing stuff if everyone else has to do it
that last 3 m3 soakaway cost 1200
:O
LLL


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33 replies since 09 July 2006,17:55 < Next Oldest | Next Newest >

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