I need to put in a french drain around my house i have a well less than six meters from the high side of the house should i put the trench for the drain between the house and well or behind the well? 😯

We’d need a picture at least…

Please excuse the mess we are still working on the house

the long view is the garden that slops down to the house infront of the house is a road and 150 meters across the road a canal the other side of the canal is a river we are in a shalow valey soil is clay.

What’s the water level in the well?
Is the French drain going to connect/discharge to something or is it going to be used as a soakaway stopping water getting to your house?

I’d probably just run it between the house and well.

We have just had mega rain the most in 100 years and the level in the well is less than a meter below ground level I have only been here 6 months so dont have much idea of normal levels but previous observation put it at closer to 2 meters below ground level, the intention is to discharge to the storm drain system my idea is to put a barrier trench across the garden and connect to the storm drain

any advice ?

Sounds like a plan.
When you storm drain system is this a ditch/culvert outfalling to the canal, or the public surface water system?
Just make sure you know who owns what you’re connecting into* and have the relevant approvals. Or connect under the cover of darkness!!

*lead local flood authority (LLFA (sometime the local authority)) internal drainage board (IDB), hopefully not EA or water authority.

Have a perforated pipe running at the bottom of 500mm-1m(ish) deep stone filled trench and connect that to the storm drain. Should take most surface run off and ground water away from the house if water levels get too high.

I’m still not clear what you’re actually trying to achieve with this land drain.

Strictly, a land drain is used to reduce groundwater level locally. Do you have a boost garden or something?

I have water ingress in he basement so yes i want to lower water level behind/around the house there are land drains which drain into the village drainage system but they are clay pipes 100 years old and blocked/collapsed people planted trees on top of them the trees are now gone.

the intention is to connect through connections already in place to the council/commune surface water system

Ah, if connections already in place then no worries. Are you taking the land drains below the basement level/are the existing land drains below basement level?

I am a chartered Engineering Geologist & Hydrogeologist so will have a go. Your water table is essentially the top of the well level (1m below ground level)(elevation head (M) + Pressure head (M)= Total head). You can simply test this by digging a small trial pit hole with a spade about 10m away from the well and seeing the next day what the level below ground the water sits at.

Your basement floor sits 2m below ground level and you want to lower the surrounding water table… this is a huge task and one that hits projects like Cross Rail, mega basements, tunnelling and any huge underground excavation hard. They solve it by compensation grouting and cut off bored & sheet piling which are not an option. The issue is clay is incredibly slow draining, typically water can take 50 to 70 years to pass through 1m of clay. Try putting a cut off drain between the house and well, it would definitely reduce surface run off. If the water is seeping through the basement wall its a big, mucky expensive job of boring through the walls and injection grouting.

@ coconut omg now Iam scared 😯 the basement is only 700 mm below ground Iam thinking a trench about 1200 between well and house might do the trick.

the well level is currently 500mm below ground level(just measured it) but as i said this is exceptional conditions at the moment.

@ads678 yrs land drains are below the basement floor i have access to one that is working all be it slowly but water escapes without flooding the basement
the issue is the other corner of the property where the land drains are blocked collapsed some one planted trees and a hedge over the drains.

Hey it’s not that bad really. If the concrete floor of the basement is only 70cm below ground level. I had it in my mind it would be 2.0 to 3.0 m below and you had waist deep water. The top of the well is very high so assuming you have had torrential rain and flooding recently this is not the “normal average” water table. The water table rises and falls far greater than most people realise and this is often a contributing cause of slope collapses on railways and motorways etc. In summer your water table could be 4.0 to 6.0m below ground level and rise to 0.50m in flooding.

Simple answer = don’t be stressed, it can always be fixed. Dig out a small trench 1.20m deep and put in a 15cm or 20cm diameter perforated pipe. Backfill around the pipe with “pea gravel” (or some course gravel, but NOT sand or finer as the pipe will silt up). Connect up the pipe to a stream or drain which is lower than 1.20 mbgl so you have a good “fall” on the pipe. I would do the drain 4m around the perimeter of the house roughly and between the house and well.

Also an overlooked answer = why not just deal with the occasional flooding – move valuables out the basement, waterproof any brick work with a silicone based weather proofer and put things off the ground.

add – wrap the perforated pipe in a geotextile to help prevent it from silting up. Something like a “Terram Geotextile”, anything that acts as a filter:

http://www.terram.com/products/geotextiles/standard-filterseparators-general-construction-highways.html

Coconut, I’m a Civil Engineer, please MM’s or M’s only. CM’s are for school kids or people with no technical knowledge. Otherwise I concur!!
😉

sorry.. 😀

sorry.. 😀

Yes conditions here are exceptional the worst flooding in France for 100 years the Seine rose 6.7 m villages have carp swimming in the streets it has been biblical.

But a neighbour tells me this has occurred to my house before and I ant to use the basement for an office.

Would it be worth fitting a pump to the well to operate when the level is high?

PS, thanks you guys for the advice you definitely earned a beer if your every in the Cher.

Start off with the simple land drains. Smaller versions of these:

https://www.google.co.uk/search?q=counterfort+drain&biw=1344&bih=707&source=lnms&tbm=isch&sa=X&ved=0ahUKEwie1Kn515rNAhWqDMAKHTamAQMQ_AUIBigB#tbm=isch&q=french+drain&imgrc=e5ksxqXy7FUf-M%3A

The issue with pumping the well out is the soil is clay and pretty impermeable. You will drop the well level quickly but there will be no surrounding draw down. It is a solution in granular soils which are permeable and many structures operate dewatering pumps like this.

Have recently installed land drains due to clay soil garden and found http://www.pavingexpert an excellent source of info. Also basement flooding common problem in USA and came across many sites with ideas how to deal with problem try www. Askthebuilder for ideas on basement drainage and regrading land to divert water.

Thank you that’s a very informative site oreetmon

I have similar issues with our lawn – here in switzerland we’ve had a very wet winter and spring… june is proving to be very undecided with regards to sun/rainfall…

This has drawn our attention to our lawn, and the clay soil.. we may have to install some sort of drainage – but how to get the necessary fall? can we link it in the our developments drain? as we have a pretty flat plot and is surrounded by the develpments roads..

Update

I have put in a land drain between the house and the well 1000 mm deep soil in the trench was perfectly dry at that depth yet 3 meters away I have a wooden veranda against the house covered with clear corrugated poly sheets open on two sides no signs of condensation on the roof but this area stays permanently damp.

The well level has now fallen more than 2000mm and I can see invading roots in the well several large trees close to the house were felled before i bought the place, I was wondering if these roots could be causing the damp problems?