Land Drainage

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Hi,

We bought our house 6 months ago. The last house had no garden, so as you can imagine couldnt wait to get out there and enjoy it. All grassed so a nice blank canvas. All seemed ok in the summer until september time when the garden turned into a sponge! Which explained why a lot of the veg my mrs planted when we moved in rotted away.

The house is 5 years old, and a corner plot in the cul de sac. I dug a hole spade deep in the middle of the lawn and the hole filled with water straight away. On further investigation of the soil it turns out its mainly sand in places, just over a foot down is a layer of clay. Been doing a lot of research and decided in spring and going to go the land drain route.

Im going to be building a workshop to the side of my house , but before I put the concrete base down im thinking of putting a:

Drainage Block Graf Rain Bloc 300

http://www.rainwaterharvesting.co.uk/proddetail.php?prod=360014

Then the base on top, then to bring all the pipes down to the bloc:

gardendrains.jpg


Theres a few things im not to sure on, is there a minimum distance there needs to be between the pipes? how much pea shingle should be under the pipes? and finally whats the best size pipe to go for, 80mm or 100mm?

Thanks in advance

Gaz
 
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breezer

If your land is clay, where is the water going to soak away to?
 
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When I move the shed im going to dig a hole first and see if its clay under there and more to the point if I can dig past it in reason, I can visualize the great escape coming on here.

The garden is about 30ft x 30ft then the side bit where the shed is currently, prob about 30ft x 20ft

I was looking to drain into the surface water drain but im not to sure whether there already is a soak away in, if there is that would be a bit pointless. Ive heard people say you need permission to drain into the surface water drain because of contaminents in the soil etc and also blocking the drain with silt.

Although if all this goes ahead then I might be able to get a mini digger on hire :D

Gaz
 
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the maximum distance between the pipes should be about 5m. you can go closer but there is no real need.

use 100mm pipe, a roll of it is cheap and it will carry more water. When we have installed them its been on heavy clay. we normally put a couple of inches of 20mm gravel down first as a bedding and then cover the pipe up to the existing ground level with gravel so it is all ready to receive the new topsoil.

i would dig a new soakaway, if there is no other way of draining the water, and put an overflow on the soakaway that is connected into the surface water. The clay will let some water soak through, but it will also act as a holding tank if necessary

we did this garden which was on heavy blue clay. We put 3 pipe runs in across the garden, one at the bottom of the top slope, one in the middle and one at the bottom of the lawn, all connecting into a pipe at the edge of the lawn. Its as dry as a bone and works very well in the wet weather.

pipes going in before covering with shingle

pipes covered with shingle to existing ground level and then covered with sandy loam topsoil

the whole area at the end
 
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Thanks Thermo, thats given me and the mrs a lot of hope! although she has just given me an idea as well, reading about your overflow from the soak away, I could as im using crate system put a pump in there to pump some water out into water butts to be used later in the green house etc. bit like a sump pump fitted in a cellar.

Not starting work until late feb, let the ground dry out a bit and thaw out.

Thanks again for the advice, most appreciated,

Gareth
 
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Just one thing to check before you expend a lot of energy/cost.

If the water table level in your area is high, their will be nowhere to soak your water too.
If in February when you dig a deep hole, and it fills with water, your drainage will have nowhere for the water to soak to.
Do you live in a low lying area? do your neighbours have the same problem?
 
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Hi Trazor,

I live in the wirral not sure what the water table level is in Ellesmere Port, had a search but came up with nothing, all I can say is its a very flat area bit like holland :LOL: previous holes ive dug in the garden over the last months have filled with water straight away, but noticed the soil is 98% sand at the surface in many places.

Dug a test hole today where I plan to put the soakaway, went down about a foot and hit heavy compacted clay/soil with a shed load of building materials dumped in, including what looks to be a scaffold board! but didnt fill with water today. not rained for a few weeks though.

I think half the problem is after the top soil was dragged away before building commenced the land had a lot of heavy traffic over it compacted it hard and lots of waste material dumped in to, then the top soil dumped back on top. I spend a lot of time on building sites so know how much crap is dumped and covered over. Not ideal!!

Gaz
 
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We had a nightmare when we first moved in with the lawn not draining, hired a mini digger (£110 for the w/e) and went for it, used land drain with geotextile wrapped round it.

Set the fall for the nearest surface water manhole, works a treat, only problem is that in summer the area of pipes dries faster than everywhere else so you have a nice feight outline on the lawn of the location of the pipes.

I quite like that really as it shows where all the hard graft went!!

Good luck
 
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Hi Redpis,

What soil type do you have? is it heavy clay?

Thanks for the photos, mrs understands what the scale of destruction is going to be!!

Have you anything in place to stop any silt from entering the surface water manhole? Although I dont think this makes any difference as you get everyday build up of crap on garden paths any way and when it rains get carried down to the grids any way.

Thanks for this

Gareth
 
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you wont get much, as the gravel will act as a filter medium. I prefer not to use the geotextile as it can clog over time.
 
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The soil was heavy clay, every mini bucket load had to be crowbared out from the scoop, nightmare.

In hind sight bearing in mind what Thermo has said, I would not use the geotextile, I've never done anything like this before so thoght I was being clever :oops:

The inspection pit had a spare blanked inlet, dug down to expose the outside of it, used a peice of pipe into the chamber and threaded the perforated pipe through it to make a seal with the chamber.

I do have a couple more pics somewhere if you wanted to see.
 
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Hi Redpis,

Yeah if you could post the pics up will be appreciated.

Just waiting for the weather to warm up at the moment before I start it all.

Thanks for the info.

Gaz
 
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Well you did ask for it/

 
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Cheers for them mate, its like a step by step guide :D cant wait to get in the digger now!!!!!

Will let you know how I get one!

Gaz
 

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