How to install drain near house?

[nboucher]

Hi members 

My wife and i moved into our new house in March but noticed in heavy rain water pools a lot at the side of the house.

I was planning to dig a deep trench to put an ag drain (filled with drain coil layered with landscape fabric and gravel) to trap the water and send it down the hill.

I was going to ask if there are risks doing this or if i should call a plumber for advice? Maybe the drain needs to connect to storm water? I dont mind that this water dumps to my backyard since that is where it is going anyway. I would prefer it trickle rather than guah from a pipe, but its not the end of the world.

I have attached some photos with some poorly drawn explanations. Blue is where water is pooling and dumping mude on the bricks under the cladding on my house and all over the pavers.

Red is where i anticipate  digging a trench and installing the drain to push the water away from the house.

 

 

[Bandicoot]

An ag drain may not cope with heavy rain unless the trench is backfilled with pretty coarse material and you can somehow prevent it from being blocked with the mud.  Suggest create a shallow surface drain lined with gravel or crushed blue metal to prevent erosion, and relay the tiles so that the water drains into it.

[JacobZ]

Hi @nboucher,

Thank you for your question and apologies for the delay in response.

It looks like your house is on a gradient, but it is hard to tell which way it is flowing. Can you provide some context on the gradient of your yard? 

The gradient I see in your photos and the advent of pooling on this side of your house makes it looks like a good location to start the drain, but if you can have this trench follow the natural water course further into your back yard, then it will manage the water better than just placing it in an arbitrary location. I'd suggest observing your yard in a downpour and see where the water is flowing naturally so you can plan the location of your drainage.

Without seeing how much water you are dealing with; I'd look to maximise the capacity of the drain. I'd suggest digging your trench 400x400mm and lining the trench with geotextile fabric membrane. Add a layer of drainage gravel 100mm thick to the base of the trench then place 100mm x 20m Socked Slotted Draincoil along the length of the trench. Backfill the sides of the trench with drainage gravel and tamp it down to lock everything in place. Add 100mm of drainage gravel on top of the agi-pipe before wrapping the geotextile fabric over the top like a burrito. You can then backfill with soil and tamp it down to finish off. Keep in mind that this drain will need to slope away from the house to ensure the water flows through the pipe instead of sitting stagnant.

If you have some photos of your backyard and any idea of where you want it to discharge, this will certainly help. Ideally, it will be connected into council stormwater pipes, but it looks like your house might back on to bushland, which would likely mean there are no council services at the back of your property. Two options that can be used in this case are a swale or a soakaway pit.

Check out Rainscaping: Rain gardens, buffers and dry creekbeds from @DirtMonkey as an example of a swale. There's also some great information in Amateurs Making a Swale, Advice Needed from @ivanptr. A swale is a great way of slowing down water so it will dissipate more evenly preventing erosion at the discharge point. They can be made to look great and can be a wonderful feature in your back yard.

A soakaway pit is another option that is essentially a hole in the ground filled with drainage gravel and Strol SureSoak Cubed Stormwater Crates. Water discharges into the pit, gravity pulls it down through the pit where it then dissipates into the earth at a lower point. This is also a great option if no stormwater services are available.

Allow me to tag @Dave-1 and @Nailbag for their thoughts. 

Let me know what you think and if you have further questions, please don't hesitate to reach out.

Jacob

[Dave-1]

Afternoon @nboucher 

Ohhhh yeah stormwater to play with is my first thought

I am after some of the same answers that @JacobZ has asked

Mainly which way does the block slope? It looks like it slopes down from the road? 

Swales and Berms are a really good way of slowing excess water and also charging your land. I have installed them in my front yard and I really believe they have helped at the very least from storms sheeting water across the yard. See Stormwater update April 2024 it really shows how I was thinking and how it worked

Down the side of your fence towards the road looks like there is a solid path? Does water pool there or flow back towards where your blue lines mark it as pooling?

I have used 100mm socked ag pipe and I do like how it works. However I really like straight 100mm PVC pipe with grilled drain pits that capture the water and then the PVC pipes funnel it away to either stormwater or Berms/swales. I like them as they are easier to maintain and the smoothness also stops them from clagging up. They are installed the same way as the socked pipe as in gravel surrounds the pipe. 

In your instance you could have a couple of differant connections, a pit and a long grill drain to cover that pooling area. As you are just starting to landscape your yard things may change down the track. So for whichever way you decide to go for a drain, consider what is in your yard, what you may want to install down the track and especially any pathing. My answer always is sketch out the yard as is, then sketch another picture of what you want, then yet another with the services that you expect to need. I push hard points on my sketch pad to transfer the points through the pages. It helps me "see" down the track. 

One lastthing, a stormwater drain dosnt have to have much fall on it anddepending on where you live dosnt have to be too deep. I would recommend tho around 500mm deep (from the start) This is mainly if you decide to install a footing or pathway down the track.

Dave

[DirtMonkey]

A "french drain" (what JacobZ suggested) in the red region next to the pavers is probably your best bet, but then you need to have it lead somewhere downhill.

Here's a trick i came up with for working out "where the water WANTS to go" with the current grade of your land. It's like a hydrogeology simulation... but its in real life!

• Get a large water-tight object (like a storage tub, at LEAST 20L) and take it to the start point where you want to "predict the flow". Don't do this at your pavers, because you already know they flood. Do it half way along that red track you marked in your last photo.
• Fill the tub with heaps of water (but not too much), then get 1 or 2 garden stakes or sticks.
• Now, tip that entire tub of water out up hill (or as close to up hill as possible). You don't want the tipping action to push all the water in any particular direction. If your shoes get wet then you're doing it right.
• Now chase the water! Drop a stake at each spot the water seems to run toward, but suddenly stops at.
• This will map all the potential endpoints of a "flooding downpour"... Downhill spots where water accumulates are ideal for a rain-garden; slow water infiltration in a planted zone. Downhill spots that stayed dry are ideal for a soakwell; you don't want to put water ontop of water, you want soakwells to infiltrate in areas that dont already have water.

[Nailbag]

Hi @nboucher 

I think the advice that @JacobZ is probably the best course of action. The one point to highlight is that you legally can't connect to the storm water system without being a registered plumber.

My advice would be to follow Jacobs advice in doing all the labour work in digging the trench, which will need to be about 300mm deep. This will save you the cost of a plumber doing this work. Then use the plumber to run the pipe and make the connection to the stormwater which will also be the best solution.

Nailbag