SEE INSIDE A RAINGARDEN PLANTER
Thinking about building your own raingarden planter?
This shows you what’s inside a raingarden planter and includes some tips for getting started.
First, have a look at the downpipes coming off the roof and think about where could be a good place for a planter. Is there somewhere where you think people would enjoy watching the water splashing down, a place where it might be nice to sit next to plants, or a place where someone could look at the plants growing in the planter outside the window?
When you have found a suitable drainpipe, you need to make doubly sure that it is a rainwater pipe, and has not had other pipes connected into it. See if you can see the gutter that is feeding it and follow the line of the pipe down the side of the building.
Next, find the drain that the pipe goes into – this will be the drain you should try and connect the drainage of your planter back into unless it is going into another raingarden.
You should make sure you seek professional advice if you need to move a connection. The raingarden planter we’ve installed at CSGNT has its outlet at the back, and goes back into the same drain the downpipe would normally go into.
The next step is to choose what you will make your planter out of. You need a watertight box, strong enough to hold all the layers of soil and gravel and also the weight of rainwater and plants. People have made planters from IBC crates (that stands for intermediate bulk container), cattle troughs, wooden planters, even a wheel barrow!
You just need to make sure that the box is of a strong construction and that it is watertight. If it isn’t watertight, you can line it with PVC sheets (overlapping by 200mm and securing with PVC tape) or with a material such as pond liner.
You’ll need pipes and plumbing parts to construct the planter’s drainage, you can get ‘push fit’ parts which mean this is easier to make. These pipes will let the water drain out of the box and back into the drain.
The pipes are also set up so that there is an overflow – a bit like on a sink. If the planter box gets completely full, the rainwater will then overtop the overflow pipe and flow out to the drain. You can see how the plumbing is set up in the drawings below.
1. Once you have chosen your location, your box, and the drain you are reconnecting to, you’ll need to cut a hole in the empty box for your outflow pipe to come out of. Cut off your downpipe above the top of your box, and add a new downpipe shoe or decorative spout to take the water into your box.
Starting from the bottom of the empty box, install a perforated (holey) pipe along the bottom, making sure that there is a slight slope along the pipe. You can use a bit of gravel at one end to help with this. Connect this outlet pipe back to the drain. You should connect a high level overflow to this pipe, which will take rainwater if your box becomes completely full.
Once the plumbing is completed and has been checked carefully, you can begin to add the layers of gravel and soils. It is best to do this with the box where you’d like it to be, as it will be too heavy to move once full.
2. Add roughly 200-250mm depth of larger gravel. Make sure you give the gravel a wash so that no dirt could wash out and block the drain. Then add a geo-textile layer on top of this. This layer is to stop the two different sized gravels mixing up, but needs to be able to let water through.
3. Next add about 100mm depth of finer gravel, again after giving it a good wash, followed by another geotextile layer. This layer is to stop the layer above and below mixing together, but needs to be able let water through.
4. On top of this add a minimum 350mm of material that the plants are going to be growing in, so that they will have enough room for their roots. As a guide, this material can be made up of 55% sand, 30% existing soil
and 15% compost. It should be free draining so that your plants do not end up soggy and waterlogged. If you have clay soil avoid using this.
Below where the new gutter spout is located, you should add some decorative stones, which will stop the soil from being washed away as the rainwater splashes out. Also add a small grate or perforated cap to the top of your overflow pipe, to stop debris from washing down.
5. Finally, plant up your box with suitable plants. These could include yellow flag iris, ragged robin, cuckoo flower, cranesbill, geraniums, rosemary and thyme. You’ll find more suggestions on our website. Happy raingardening!