Friday, 27 January 2012

Garden Irrigation Update

Over the past few months, the Crew at Addison Road Community Garden have been upgrading the drip irrigation system. We consulted Emma's brother, a plumber and Hydraulic engineer, for tips on how to build the system. After an hour of discussion, we had a basic plan requiring some further investigation and project management. My studies were finishing for the year and I had some spare time so I keenly volunteered to coordinate the project with garden members volunteering to take on tasks they were interested in and could manage.

Our first major break-through came when we rallied together at a Sunday working bee and rebuilt the crumbling 'formwork' so we could get a concrete base poured for the tank. Lloyd had obtained some solid recycled wood for free so he and Gavin led us in the building of the formwork. We let the momentum carry us forward and the following Thursday we got the concrete slab poured at a heavily discounted rate by taking the leftover concrete from larger jobs. We dashed to the garden just as the truck arrived and wheeled heavy barrows from the truck to the formwork while a slow drizzle of rain threatened to wash the concrete away. Result: rain held off and the concrete base is solid.

Now this tank is only 'new' to us in the sense that we have not previously connected it up and put it into use. It was found or donated to us a few years ago and had become an obstacle in the garden that we would deal with one day. We moved it on top of the base and poured some water in it to discover that it leaks at two opposite corners. The tank is a slimline design and has structural supports inside making full access inside it impossible. And what about all the leaves that had fallen into it over the years? I didn't want to mention the leaves as I couldn't imagine how we would fix the holes and I was having my own lack of faith with some of the ideas put forward. Then the next week our occasional superhero Gavin, flies in and figured out how to remove the lid off the top of the tank so we could clean it out and do a proper repair job. Gavin then flew out as other duties were calling and Christmas hit so currently we have a half fixed tank, waiting for better weather, time and expertise.

After researching the parts needed for the dripper line, I drafted a few dripper layout schemes for discussion and we settled on a system with three zones. Zones 1 and 2 will be fed by our existing two tanks and solar powered pumps. The third zone will be fed by our yet to be fixed 2000 litre water tank.

A few weeks after the concrete base was poured, Emma called another meeting to get us back on track. We did a trial installation to get the layout concept right. Members gave some support for the design I had drafted, so the next week I headed to the hardware for parts and purchased a large brass Y-filter online.

A week later, thanks to Matt, we got stuck into the dripper-line installation for Zone 1.We immediately improved the design on the spot by eliminating some of the elbow joints as they didn't seem necessary and  it also cut down on parts and cost and will keep the water flow smooth with the water pressure higher.

The most time consuming step of the installation is peeling back the weed mat under our path and digging short trenches down about 6 inches deep to connect new pipe to the existing main water line. Once this has been done, it's a fairly simple job of connecting an inline tap with black polypipe and 3-4 metres of dripper line. We've had this dripper line for years, donated to the garden waiting for us to figure out how to us it. It has drippers inside the hose installed during its manufacture and spaced every 30cm.

Many of our gardening crew had been developing an almost desperate desire to get the irrigation system up and running before the looming Christmas break. In previous years when we go off visiting friends and family over the Christmas holidays, it has been hot and dry meaning our precious garden plants die off. But ironically, it’s been slow going getting the dripper line in, partly as it has been raining so much. Hindsight is a great educator as the penny dropped for me a few weeks ago when inspecting the Bureau of Meteorology website and the Southern Oscillation Index chart. We have been in a 'La nina' pattern for the past 2 years which means that Australia gets a lot more rain. (D'oh, that's why we've had all those floods up north). Our plan for drip irrigation was born among the droughts of the 'El nino' pattern.

But drought or not, having the irrigation system fully functional will consume much less water and make watering much easier. Just before Christmas, Matt and I added a few more dripper lines when the weather was good. More recently I did some investigating with of the existing components of the system.

Firstly, I added a mains connection to compare the drip rate under pump pressure versus mains pressure. There wasn't any perceivable difference.  So then I tried to find the connection for the mainline in Zone 2, which I suspected was under our new herb spiral. I remember connecting it to a mains tap 12 months earlier but couldn't remember how I did it. So I added another mains connection to the pipework in Zone 2 and turned it on. Then came the next major realisation. Zone 2 was pressurised and Zone 1 was dripping. There was only one main line. There was never a previously separate two zone system. I seemed to recall twelve months ago, I'd connected an incorrectly plumbed inline filter to the local rainwater tap as they have the same thread. The tank and pump in the Zone 2 area was installed partly to flush a local loo. We had a tap to use the tank 2 rainwater in the garden, but we never had a connection to the old drip system.

Now we are pondering if we stay with the conceived Zone 1 and 2 or keep it as one system.

In the meantime, I found some awesome dripper line purpose build for gravity fed and recycled water systems. This will be perfect for our gravity fed Zone 3 system. Under our previous design we decided to install lots of individual variable flow drippers. This new line will save us lots of time installing and maintaining the line as the drippers can't clog up or fall apart. We just need that Zone 3 tank to be fixed and were in business.