Advice on drainage system

DarrenT

Hi community,

I’ve been a long time admirer and user of the Bunnings Q&A section as newbie renovator but never posted my own question. So here I am with a question regarding drainage recommendations for the side area of my house.
currently there is no drainage and with some severe storms a lot of surface water appears. The soil is clay and not very water friendly. Both the soil/ground and path falls into each other in a V shape so water tends to pool and build up from this location. I am currently contemplating some drainage options to helps clear the water whilst also improving the look of the side area. I have dug and exposed a stormwater drain that I can access to assist with clearing the water as there is currently no where else for the water to exit.

My current plans;

I am planning on removing & levelling the soil area and installing a small 200x 50 sleeper/ retaining wall with sleeper pegs along the bottom of the colorbond fence (not attached to the fence) . Then once level - installing approx 6m x 1.6m artificial grass underneath the clothesline area with appropriate gravel then crusher dust then sand and attached with nails and glue. The other half of the soil will be covered in weed matting then low maintenance tumbled sandstone where I will build some 2 sleeper high vegetable gardens. With all this in mind, I want the drainage to be effective so should I either;

1) Channel drain all the way down the side of the path - like the ever hard system then pvc pipe and a Y pipe to attach to the storm water with appropriate fall. concerns regarding this option surround; the cost for approx 12-15m worth of channel drain & concrete etc; achieving appropriate fall when aligned next to the path that has very minimal fall therefore looking a little strange going from level to the path to approx 10cm below the path on exit.

2) trench with french drain & corrugated pipe and fabric along the length of the path with eventual connection to pvc then stormwater pipe via a catch basin?
concerns with this- am I allowed to connect agi pipe to pvc stormwater pipe? Will this be enough to take the water away from the surface?

3; adding small trench along the path with some drainage gravel and PVC pipe - adding 2-3 evergard grate and floway pit every 3-4m to collect surface water to the pvc pipe then attach to stormwater pipe via Y connection.
concerns with this option- will this give my artificial grass enough drainage as PVC pipe will not take out below surface water.

I’ve added some photos and would be very grateful for any help.
thanks in advance,

Darren

this last photo is how it usually floods and does this usually for the length of the path.

JacobZ

Hi @DarrenT,

Welcome, it is fantastic to hear you've been a long-time reader, and I am happy to see you make your first post.

The key thing to be aware of first, is that for safety and compliance, any connection into your existing stormwater system needs to be done by a licensed plumber, so it’s fine to plan around that and lay the groundwork, but the final tie-in needs to be done by a plumber. Considering this, I would suggest you line one up early on and ask for their thoughts on what would be the best option. Their experience in this situation will certainly be worth utilising.

Looking at your options, a full channel drain along the path will work well for surface water, but it would be tricky to install neatly if your path doesn’t already have good fall. As you’ve identified, trying to force fall over that length could be difficult, and in my mind rules it out as an option.

A French drain with agi pipe is a good option for dealing with subsurface water, which is likely a big part of your problem with clay. However, on its own it won’t capture surface runoff very well, especially during heavy storms. Also, while you can transition from agi pipe to PVC, it needs to be done properly via a pit or inspection point, not just directly joined, and again the final connection to stormwater must be done by a plumber.

Your third option is probably the most balanced. Running a solid PVC line with a few grated pits along the way will handle surface water effectively and spacing them every few metres is a good approach.

If you wanted to improve it further, you could even combine elements, for example adding agi pipe underneath the lawn and garden area to capture the ground water, which then feeds into the drainage pits that are installed along the pathways edge.

Realistically, anything you do will improve the drainage, but I think a combination of your third idea and some agi pipe snaking beneath the lawn and garden areas would be the best way to go. Considering you'll need a plumber's assistance; it might be worth bringing this idea to them for their professional opinion. You can then do the work digging and installing things, with the final touches being done by your plumber.

Allow me to tag our helpful members @Nailbag, @Dave-1 and @TedBear to see what they think.

Jacob