Need to drain groundwater reemerging from dirt slope under the house

[jbs1]

Hi all, I’ve got a dirt slope under the house that has groundwater coming out of it after rainfall, washing dirt and bits of rock down onto the concrete floor of the workshop. There are piers all over the place and the slope is uneven, making it hard to find an obvious path to divert the flow using ah pipe, and I don’t want to go digging because of the piers. Any thoughts or suggestions? Cheers! Jim

 

[MitchellMc]

Hi @jbs1,

You might like to show us some images of the area so our members can get a better idea of what solutions they could suggest. Would you be able to run an Everhard EasyDRAIN Polymer Grate & 3m Prejoined Channel along the edge of the slab to a point where Vinidex 50mm x 10m Black Slotted Draincoil could be connected, diverting the water out of the area? That would only require you to dig a small trench. 

Let me mention @Adam_W and @TedBear to see if they would like to join the discussion.

I look forward to hearing more about the situation and providing a solution to your issue.

Mitchell

[TedBear]

Hi, my initial thoughts are.... where is this water actually coming from?  How long for/is it a relatively new thing?

On the theme of 'Prevention is better than cure'   it may be worth trying to see why a stream of ground water is coming toward you.

I had a similar issue in a house many years ago, where a room had been added lower on the block - i.e. it was a step-down room below the house's normal floor level, with a concrete floor. That house was on piers too. After removing smelly carpets after every winter, I eventually found that the driveway crossover at the front of the house (high end of block) wasn't installed correctly and was directing masses of street water into my drive which turned into a shallow stream under my house, came through a crack in the brick wall end of the added room and ended up seeping under my carpets. By the time I smelled it, the stream had always dried up. The council fixed it once informed, and I had no more trouble.

That may not be your situation, but the earlier in the system you can divert that water, the better your result will be.

I am interested to see more on what your own situation is...

[redracer01]

Hello @jbs1 

Welcome to Bunnings Workshop! I am a firm believer of DIY channel drains. I strongly believe in working with nature and not against it. So my solution for you is a two step approach. First I suggest creating a shallow U shaped water drain. It's also know as a spoon drain.

- Prepare your proposed area of the channel by creating a shallow channel about 30mm deep and then flattening it out with available garden tools. Use a level to make sure that the fall of the earth points out towards your nearest garden.

- Once you've prepared the ground you can use Bastion builders mix to prepare a cement channel about 150mm wide and at least 20mm to 30mm thick.

- Use a 2 liter bottle of coke or similar shaped bottle fill with water to prevent crushing the bottle, push down in to the wet cement channel to create the shallow U shape. Finish and feather to desired shape.

- While waiting for your cement to dry, visit your local Bunnings and buy some buffalo turf to cover the bottom area of your slope. It does not need to cover the entire slope just half a meter past the body of your diy spoon drain.

What is the turf for? The buffalo grass serves as a natural water buffer before it hits the spoon drain. The grass traps the water and the debris acting like a natural filter. Buffalo grass is very tough and hardy even in the shade so in essence if the grass survives then it should soak up incidental water. But should you get big rain then the spoon channel will redirect it to the garden. A winner in both situations, please note that in the drawing I've drawn the drain as a curve that is to just illustrate that you can build it with the turn and contour of the earth and does not need to be straight. Just remember that the edge of the drain must be level with the earth otherwise the water will just go past it and under the drain. I hope the drawing makes sense and helps you out.

Cheers,

Red

 

[jbs1]

Thanks, TedBear - your situation certainly sounds pretty challenging, requiring a fair bit of deduction. Mine is a bit more straightforward: the high side of the house had a perfectly-flat pathway of pavers, which sat on a bed of concrete and rock, and for some reason zero drainage. Surface and subsurface water would come down the hill and have nowhere to go but into the pavers and then under the house, onto a base of dirt...just had it ripped up and some drains installed, so hopefully that prevents any further issues! Cheers, Jim

[jbs1]

Thanks Red, that's really helpful - if I can't get grass to grow and act as a natural filter, what else would you suggest? Some rock/gravel encased in chickenwire? Cheers, Jim

[jbs1]

Thanks, Mitchell - that everhard drain / slotted draincoil sounds like a solid approach: would I need to put a sock over the draincoil, or anything like that? See some pics below. Piers have been recently re-done, and there's now drainage on ground level on the high side of the house, but am anticipating a good deal of subsurface water will still pop out halfway down as it emerges from some rock beds along the slope.

Cheers,

Jim

[StevieB]

Hi @jbs1,

Thanks for sharing more about your project.

Let me tag @redracer01 and @MitchellMc so they're alerted to your questions.

Stevie

[MitchellMc]

Hi @jbs1,

It's great to hear that you installed drainage on the ground level, and I feel this will really alleviate a good portion of the water flow. If you were to install the drain channel across the slope, the drain coil would remove the water from the channel to distribute elsewhere. I seem to have linked to the slotted version of the drain coil, which is not needed as you'll be using it to transfer the water instead of collecting it. Instead, Vinidex 50mm x 20m Black Unslotted Draincoil would be more suitable, and no sock is needed. Alternatively, you could dig a trench 100m wide and 30cm deep around the perimeter of the concrete slab. Drop Vinidex 100mm x 20m Socked Slotted Draincoil into the bottom and backfill with Ki-Carma 20kg 10-20mm Drainage Gravel. The pipe would be run out from under the house and ideally to a stormwater collection pit.

On a side note, this is a very similar situation to under my house except the water can not escape and pools. After the recent torrential rains in Sydney, I had at least 35cm of water sitting there at the bottom of my slope. I'd estimate around 3000 litres that couldn't go anywhere. I'm in a rental, so adding drainage isn't an option for me.

Mitchell

[jbs1]

Thanks Mitchell, appreciate the advice; that's an approach I think I'll use over the summer, thanks for the links to the products too. I hope your place dried out ok! Cheers, Jim