(see also Renew Magazine no 146, page 81-82 of the electronic copy)
A couple of years ago I built a small and simple self-watering system out of four recycled PVC pipes and plastic pots. It hangs on a very sunny wall and holds 39 pots, which I use to grow alpine strawberries, vegetable greens, leeks, larger seedlings and the likes.
How it works:
The pipes are laid horizontally and have large holes drilled in them to hold plastic pots. Long wicks (reaching halfway into the potting mix) are installed in each pot and absorb water from inside the polypipe. This allows the bottoms of pots to sit above water level, preventing anaerobic fermentation of the soil mix.
The benefits:
Space-saving. For those of us who have limited space (balconies or small gardens) it makes sense to go vertical.
Water saving. In a closed system with water coming directly into the root zone, the only evaporation comes from plant tissues, not from soil surface.
Self-watering. Depending on the size of the plants and the weather, sometimes the water lasts for several weeks. Pick up one of the pots weekly to check the water level and top it up through the pot-holding opening. You can also fertilise the plants at the same time by adding diluted worm juice or seaweed extract to the water (this is called fertigation).
No mosquitoes. There is no access to the water which prevents mosquitoes from breeding in the pipe.
No root disturbance when moving plants. Because each of them sits in its own pot, when you harvest or replace a plant you don’t disturb the roots of the neighbouring ones.
I’m sharing instructions on how to make such wicking polypipe system to encourage readers to grow food where space is at premium – on balconies, terraces and townhouses.
What you need:
- A length of PVC pipe* (water and sewage pipes are 100-150 mm in diameter, orange electrical PVC pipes come in sizes up to 225 mm)
- PVC caps to seal both ends of the pipe (and silicone sealant to do so)
- An electric drill and a drill bit with a hole cutter. For a 150 mm diameter pipe I used the 110 mm cutter size (which fits standard pots 140 mm wide) and 130 mm cutter for larger, non-standard pots
- A pencil and a ruler
- A small metal file or rough sandpaper
- A few palm-sized pieces of flyscreen
- Plastic pots (I source mine from a recycling box at a local garden centre)
- Offcuts of geotextile/agfabric or another dense, fluffy artificial fabric (polyester fleece or similar) to make water wicks. Simply cut the fabric into 25 cm by 3 cm stripes.
- Outdoor paint*.
- Materials for supporting frame – see instructions below
* I would suggest painting the pipes to protect the PVC from deteriorating in the sun.
Preparation:
- Cut the pipes to the desired length.
- Draw a straight line along the pipe and mark the centres of pot-holding holes on it (I drilled mine 160mm apart for 140 mm pots).
- With a normal drill bit, drill small openings in the marked spots – they will serve as anchors for the hole cutter.
- Using the pre-drilled holes, position the hole cutter and drill large holes.
- Using a file or sandpaper, smooth the edges of the holes.
- Place a pot in one of the holes and have a look into the pipe to check how deep the pot sits. This is to determine where to drill an overflow hole in the pipe end caps. The overflow should be about 5 mm below the bottom of the pots to avoid flooding the soil. Mark it on the cap.
- Drill the overflow hole (about 4-5 mm wide) in one of the end caps and cover it from inside with a glued-on small piece of flyscreen to create a mosquito barrier.
- Glue the caps with silicone to the ends of the pipe making sure the overflow sits in line with the pot holes.
- Paint the pipe.
Support frame
There are many options depending on what materials you have available. My frame (pictured) is built from recycled hardwood fence posts, standing on concrete and screwed to the house’s wall.
I have seen metal angle brackets attached to walls and pipes hanging from balcony railings suspended on thick, galvanised wire bent to fit two pipes: a smaller one inside the balcony and a bigger one outside the railing.
Whatever frame you decide to build, make sure it can carry the combined weight of the pipe, as well as pots full of soil and water inside the pipe. My 150 cm polypipes can weight over 30 kg each when fully planted and filled with water. Don’t use guttering brackets unless your pipe is short as they will bend and collapse, not being designed to bear weight.
Preparing pots:
Push one or two wicks through pot bottom holes, so about 15-20 cm of fabric hangs down from the openings.
Add potting mix of your choice and fill each pot halfway up, making sure the wicks are stretched up through the soil (not just along the pot walls or squashed at the bottom).
Plant the pots, adding soil to the brim and water well.
Put them in the already installed polypipe, but leave one pot aside, so one opening is empty. Use it to fill the pipe with water until it reaches the overflow hole (this is also how you top up the pipe and add liquid fertilisers). Place the last pot in the last opening, sealing the system.
The wicking polypipe is a great and simple project to do before summer arrives, with heatwaves and time spent away from garden. Try it, I guarantee you’ll be happy with the results!
What a genius idea, perfect for our small courtyard and bonus that it doesn’t attract mozzies.
I appreciate the instructions, looking forward to starting a project like this for summer!
Henry
Hi Henry, I’m sure that when you build your system, it will work well for you! Share some photos, please.
Thanks for the instructions, it 2aa easy to make and I look forward to not having to water so often!
I am trying to heal myself and would love to attend some of your workshops. Could you let me know when you have your next one?
Hi Lucy,
I do not have any public workshop on herbal medicines scheduled for 2017 so far. If you are in Sydney, perhaps you would like to organise a few friends for me to run a private workshop for you? Please email me on info@mosshouse.com.au
Hi! I have a 75mm PVC pipe leftover from our Halloween Covid “Candy Slide”.
I’m thinking about trying this, but wondering if you see any issue with either:
– Using a 70mm hole cutter and using taller fluted pots with a 7cm bottom diameter, 10cm top diameter, and maybe 150cm tall
– Using a saw to cut several rectangular holes for longer and shallower containers (think 40cm long, 20cm deep, 6cm wide on bottom, 10cm wide on top)
Would the self-watering system still work with different shaped pots than the ones you used?
Your thoughts would be so appreciated! Love from Canada.
Hi Meagan,
Wonderful to see the idea of wicking pots in a polypipe went across the ocean!
The shape of the pot/container doesn’t matter as long as the wick is stretched up at least halfway into the soil. For rectangular containers you would need 3 wicks.
If you use social media and post a picture of your system there, please tag me @moss.house.au on Facebook or @mosshouseau on Instagram, I would love to see what you did.
Cheers
Margaret
Will do! Thanks so much Margaret. 🙂
Would it work to have the cloth enter the soil from the topside, with the other end of cloth piece in a bucket of water? (The idea to allow plants to last a month on their own.) Thanks!
I saw it done, but in temperate climate. How long this way of watering works, depends on the temperature, wind, and density of the cloth. If it’s hot, in a month the whole bucket of water would evaporate. Wind will dry out the wicks. Another way for this system to work longer is to put the plants indoors.
Fingers crossed that your plants survive!
Cheers
Margaret