My garden drainge plans - i need your advice - Plans for garden drainage

[Joystick]

I am looking for a bit of experience / expert advice on my plans and possible options. I have read so much on this subject from many forums and expert web sites so am nearly there…. But have some specific questions before I spend lots of money and break my back! So sorry for the long description!

Usual story, Garden flooding, clay subsoil!

The garden (12m * 27m) slopes away from the house by 2ft over 27m. All adjacent gardens are higher at the bottom where my garden’s lowest point is. At this point the clay starts about 18 inches below the top soil.

My plan to improve the situation is as follows:

1. Install a large 200- 400lt approx perforated sump chamber 1m deep at the lowest point. support the circumference with 20mm gravel for as large an area as practically possible. This will the centre point of water collection supplied by ground water and French drains.

2. Install network of French drains approximately 2ft deep with 100mm perforated land drain pipe throughout the garden and connected to the Sump. All backfilled with 20mm clean gravel before laying (sand?) topsoil / grass. (whats the most efficient thickness of soil and grass for the perfect lawn!)

3. The sump will be ‘Pumped’ out to ‘the front garden create soakaway’ where it will naturally find better drainage – I am aware of the restrictions of connecting land drainage to United Utilities foul waist.

Questions:

1. what’s the best product to use for the sump container? I can get civil products from £100 + vat ish but want to save money…..Was thinking about 4 large old car tyres bolted together and I will make lots of small holes in it!

2. What is the most reliable 'brand' and diameter land drain pipe to use?

3. 20mm gravel? Is this the best / cost? what material is best for Backfill of posh French drain?

4. THE PUMP…. Is it worth spending the money and getting a Zoeller submersible grey water pump - 53-0065U for £200 ish or a £80 one from screwfix? I want the Zoeller, but i have to Justify cost against the budget!

5. I am going to keep ‘on site’ the top soil that is extracted for use again as top soil. All clay excavated will be removed.

I am planning to raise the level of the lowest part of the garden by 450mm at the thick edge of the Wedge. 90sqm (Effectively leveling the area to a fine edge - area calculations should be x0.5.)

The big question is.......once the infrastructure has been installed and the ground has been prepared, Should I also lay a 100mm (or more?) layer of gravel on top before newly laid top soil to increase / improve the water transport to the French drains and hence to the sump for removal?

6. Should I consider using soakaway creates while still relying on a pump?

7. Should I be using membrane sheeting around the land drainage pipe? Brand / Specification?

8. AM I ON THE RIGHT TRACK?

Any help will be most appreciated. I need to get this work completed before I start building a 34sqm extension to my house in the spring. The building part I can do!

I just need your experience in drainage! And thank you for reading this!<span style='font-size:19pt;line-height:100%'></span><span style='font-size:19pt;line-height:100%'></span>

[GB_Groundworks]

Why not get some one who knows what they are doing in rather than a guy and mini but no idea what he's doing?

You can't just fill ontop of the soil that's there, you need to strip the existing organic matter and then fill with suitable fill material, which in your situation I'd want to be very sandy or stoney.

You fill your low spot with soil on soil you'll get a swamp

Can you fill without retaining the full or are you going to cover fences etc

160mm is way to big, 80mm more than fine

Gravel filled soakaway/attenuation cells are a waste of time. The small gravel fills all the voids. Either make your tire one with spacers between tyres but wrapped in geo textile and put a slab lid on it

to fill 112m2 by 450mm youll need 110 tons of fill

you might get 3 tons out of your drains if that depending on what bucket your man has,

top soil is no good for filling 450mm

plus like you say pumping it into the drains is gonna come back and bite you in the arse, when you sell you are going to have to declare it or remove it.

you not fancy a little pond at teh bottom of your garden?



Edited By GB_Groundworks on 1390157400

[Joystick]

Thank you GB_Groundworks. These are exactly the points that i need to think about to ensure that the work i do (and money i spend for materials) is firstly the best solution both in cost and best practice then secondly ensuring that we won't have any problems in the future with either us living here for the rest of our life's or selling.

You have given me some homework to do before i come back with my revised plan and more detial!

Thank you.

Should be back with update tomorrow night.

p.s Any more thoughts on the pump?

[msh paving]

A good quality stainless steel pump, you would expect to pay about £185 ish for it, forget the cheap plastic ones, I fit stainless ones in sewage treatment plants 24/7 pumping 4 years life ish

MSH

[Joystick]

Thanks msh paving, its what I want to hear!.

I HAVE EDITED MY ORIGINAL POST TO REFLECT MY IMPROVED PLAN AFTER 'GB_Groundworks' VERY HELPFUL ADVICE / COMMENTS

Comments on the new plan are desperately very welcome.

And thank you all again.

[GB_Groundworks]

Questions:

1. what’s the best product to use for the sump container? I can get civil products from £100 + vat ish but want to save money…..Was thinking about 4 large old car tyres bolted together and I will make lots of small holes in it!

dig your hole, line it with geotextile, drop your tyres in and then surround it with gravel, use a 600x600 slab as lid,

we'd use a proper perforated chamber ring



2. What is the most reliable 'brand' and diameter land drain pipe to use?

80 or 60mm more than fine for your garden, we use 80mm fingers connected into 100mm main for a full rugby pitch

the blue stuff is better quality, wavin or poly pipe but any will do for your garden as its not like a 10 ton 4x4 tractor is going to come ploughing through it



3. 20mm gravel? Is this the best / cost? what material is best for Backfill of posh French drain?

we use 40mm clean stone in fields, 10mm clean in sportsfields

but for you bulk bags of pipe bedding will be fine

4. THE PUMP…. Is it worth spending the money and getting a Zoeller submersible grey water pump - 53-0065U for £200 ish or a £80 one from screwfix? I want the Zoeller, but i have to Justify cost against the budget!

asked and answered

5. I am going to keep ‘on site’ the top soil that is extracted for use again as top soil. All clay excavated will be removed.

I am planning to raise the level of the lowest part of the garden by 450mm at the thick edge of the Wedge. 90sqm (Effectively leveling the area to a fine edge - area calculations should be x0.5.)

The big question is.......once the infrastructure has been installed and the ground has been prepared, Should I also lay a 100mm (or more?) layer of gravel on top before newly laid top soil to increase / improve the water transport to the French drains and hence to the sump for removal?

you should use an non organic matter free draining material for your fill, sandy gravel type best,

6. Should I consider using soakaway creates while still relying on a pump?

only if you create a soakaway then an overflow into a chamber for the pump

7. Should I be using membrane sheeting around the land drainage pipe? Brand / Specification?

terram 1000, you can buy pre wrapped pipe but its expensive and in a garden a waste of time

8. AM I ON THE RIGHT TRACK?

sadly clay ground is very hard to drain, and if you go over board spend £10k you then end up desicating your garden and its brown in summer, although summer hasnt really happened for a few years.

Any help will be most appreciated. I need to get this work completed before I start building a 34sqm extension to my house in the spring. The building part I can do!

I just need your experience in drainage! And thank you for reading this![/b]