Tuesday, 16 March 2010

Low Pressure Drip Irrigation

by Gavin from The Greening of Gavin

Just before Summer here in Australia, I decided to install a cheap and efficient drip irrigation system.  I originally published this in three parts, so to improve the flow of the post, I have compressed it into one long story. 

Due to the limited space I had available, I figured that small was the way to go, so I rushed down to Bunnings (our local hardware store) and bought two 100 litre water butts to start the irrigation system that would be fed from the overflow of my existing 2300L tank.  As soon as I got home it poured down with rain, and I quick gave the butts a quick rinse to get rid of the plastic bits from when the manufacturer drilled the hole for the tap.  I put one on at ground level and I put one on an old pot for better pressure.  I then filled them with the garden hose connected to the main tank and filled them up.  So far so good, I though, but then it started to pour down with rain and I got drenched.  This is what they look like later on in the afternoon, fully hooked up to my new system.

The tank quickly filled up again, and I was back to square one, with no way to get the water to the garden because I hadn't gotten around to connecting anything up.  So, after a quick lunch (still raining), and about an hour of planning how it was all going to go together, I made a comprehensive list of parts required and I headed off to Bunnings again, then purchased about $150 worth of plastic fittings and a 200L rainwater butt to add to the system.  I also bought 4 hebal eco-blocks to make a stand for the larger butt so that it was above the hight of my garden beds to ensure that gravity did its work.

When I got home the rain was just easing off and now a steady drizzle set in.  Wonderful stuff to work in and I had to wear a ball cap to stop my glasses from misting up!  I fully dismantled the old irrigation system that had gone unused for so long.  It consisted of a 24v solenoid, about 8 metres of 19mm poly pipe and lots of clips and elbow joints.  It took about an hour to dismantle and remove the wire run which fortunately was only cable tied to one of the electrical conduits running along the top of the car port.  I had kept heaps of other long 19mm lengths and lots of 13mm pipes saved when I ripped out the system in the front lawn.  So, I found a suitable length on 19mm pipe and pushed it behind the water tank.

Then along the front of the deck, past the worm farm, behind the conifir and it just reached the front of the garden bed.  Excellent I thought, and began to start work on the tank end.  I am so glad I had the forthought to install an isolating valve before the brass tap, which made things very easy to install, with no water loss.  This is how I connected it;

I removed the old brass tap, connected a male to male 20mm plastic riser pipe, then added a standard tap fork with two little taps on it and screwed a standard quick clip nozzle to one side so I can still connect the garden hose to the tank if needs be.  To the other side I connected a female to female 20mm pipe to a 20mm male to 19mm barbed connection and with a series of 19mm elbow joints connect it to the main 19mm poly-pipe.  All nice and neat and I made sure I used Teflon plumbing tape around each of the threads to stop leaks (a valuable lesson learnt from installing the system on the other side of the house).  A quick test to see if water came out the other end of the main line 19mm, and then a pressure test to check for leaks by putting my thumb on the end.  No leaks thank goodness.  Then I started work on the solenoid so that I could use mains water twice a week via my automatic sprinkler system.  This is how I put the next part together;

I cut the main 19mm line at the bottom, inserted a 19mm T piece and then hooked up the solenoid to the wires and to the mains tap.  The wires were already there from the old system so there was plenty of length to connect to the electric valve.  The solenoid prevents rainwater from flowing into the mains town water which is not allowed by law, and I added another lever tap just to make sure I can isolate it further if I ever need to (I have since installed a non-return valve as well).  I did a quick test to check for leaks between the lever tap and the solenoid valve and all was good.  It was a bit fiddly putting the pipe together between the main lever tap which was 20mm to the steel elbow joint of 25mm but luckily I had all the bits from the old system.  Then I moved on to connecting the two 100L water butts into the system.  No use having them there full of water if you can't integrate them in, I thought.  So this is what I did;

The taps that came with the water butt had 15mm barbs and no matter how hard I pushed, I could not get 13mm poly pipe to fit.  So, I trimmed a bit of normal 15mm garden hose, forced that on, and then I could get a 13mm elbow onto each butt and connected them both together.  I used a 19mm to 13mm T in the main line just behind the lower butt.  Once again a quick test and no leaks and water flowed out the end of the main line.  I now proceeded to set up a pipe to connect to the 200L water butt on the other side of the conifer tree;

You can see that I put another 19mm to 13mm 'T' into the main line and put a length of 13mm poly pipe on in readiness to connect the 200L water butt.  Firstly I had to finish off the main line pipe to the back of the garden beds.  You can see I have begun to dig away the Tuscan pebble to expose the weed matting.  I put in a 19mm elbow and ran it so that it was level with the edge of the first garden bed.  Then I dug a trench all the way along the edge of the bed and laid the main line.

This is the finished product with a length of 19mm pipe sticking up with a bung in the end, ready for the task of laying another 19mm main line across the back of all the garden beds.

I filled in the small trench and got to work setting up the hebal eco-brick base for the 200L butt.  I levelled off the bricks then laid two on top, check the level again and made sure there was enough room so that the base of the butt fit evenly on the stand.  I had to trim a little bit of the conifer back so that it was not sticking into the plastic butt.  Then came the funny part.  The 200L butt did not have a female thread pre-cut into the water butt for the tap to screw into like the 100L type, and required you to put the tap fitting into the hole on the outside and then screw another part on the inside.  The only way I could figure out how to do this (because I couldn't reach the bottom), was to turn the butt upside down, put it on my head with one arm inside and ask Ben to put the tap in the whole and I screwed the inside part tight.  It reminded me of the Mr Bean episode of the Christmas turkey on his head!  Ben and I laughed when we finished it.  The tap barb was 15mm again, so another piece of garden hose and I connected it to the 13mm pipe I had installed into the main line earlier.  This is how the connection looked.

Easy access to the tap, and now all connected and looking very smart.  Here is the 200L butt in all its glory on the nice eco-block stand.

Nice stand, and all level too.  Now, because I had put a bung in the end of the main line, and because this smaller tank was lower than the water level in the main 2300L tank, all I had to do was turn on the little tap at the main tank, and then turn on the tap for the 200L butt and watch it fill up from the bottom.  Water will always find it own level, so as long as the main tank level is higher, then I never have to drag a hose around to fill it up.  Same goes for the smaller 100L butts.  Bloody genius I thought.  I just have to make sure that I put an inline 19mm tap at the start of the garden bed system so that I can isolate all the beds to continue to use this method of moving the water around.

The next day, I went and inspected the work I completed the day before, only to find a small puddle at the bottom of the 100L water butt that I had sat on the ground.  In my haste yesterday, I had bent the tap and the rubber grommet was not forming a seal.  I lost about 25L during the day.

I decided to fix it up straight away, but as I was unable to lift the 100kg of water, I had to drain ¾ of the butt into the veggie patch before I could disconnect it.  I found a very large terracotta pot with a crack in it, so I turned it upside down and used it as the base for the water butt which gave me a little more pressure from this butt and it is now above the level of the garden beds.  I fixed up the tap, stopped the leak, and made sure that everything still worked.  All good for now, and no more leaks.

I then tested the solenoid.  I removed the 19mm plug that I had put in the end of the main line and started to manually start each of the stations on the automatic control panel.  It took a while, but I figured that it is station #2 and the solenoid works fine.  So far so good.

I then cut the main line level with the top of the garden bed, put in a 19mm elbow joint, and then inserted a 19mm in-line filter to ensure that no dirt from the rainwater tanks would block the drippers when I start the system.  I then put a 19mm in-line tap so that I can fill each butt from the main rainwater tank, and so I can isolate all the garden beds with just one tap.  It was just on sunset, and by this time I had an audience with Kim (my wife) and Amy (my daughter) watching me lay more 19mm pipe across the back of each bed.  Amy decided to help me out, so she became my girl friday and handed me clips and nails to hold the pipe in place so that I could fasten the pipe to the wooden garden beds.  At the end of each bed I put a 19mm to 13mm T piece so that I could start the next stage on the following night.  I finished the main line for four of the five beds before I ran out of 19mm hose clamps so I stopped for the evening.

I laid the main 19mm line all along the back of the veggie patch beds, and inserted a 19mm to 13mm T piece so that I rig up the piping for each bed.  This is what it looked like before I started work.  When using harvested rainwater, make sure you put in an in-line filter to stop your drippers from getting blocked.  Some silt may get into your tank so this is a simple precaution to avoid having to purge your system everytime you inadvertently put dirty water into the pipes.  Here is the filter setup;

Here is the mainline with the T pieces inserted;

So, I began by making a set of isolating taps for each bed which were all 13mm fittings.  It was a little bit fiddly, but once I made one, I managed to bang out the other 4 very quickly.  This is the mainline isolation tap and the secondary tap assembly for one of the beds;

Then I put in a secondary line of 13mm pipe, down at the level of the soil, and then ran a few tertiary 13mm line down the length of each bed and used Moss Inline 13mm drippers where there was a plant.  This is quite easy to do, but much simpler if you lay the pipe and drips before planting.  You can get to all the bits without damaging existing plants.  This is the first garden bed completed (tomatoes, leeks, and red onions);

 The second bed with three tertiary lines (zucchini, cucumber, and eggplants);

The third where I used 4mm Drip Eze by Pope irrigation systems (click the link for an installation video).  20metres cost me about $25 and I still have about half of it left over.  Each drip point in the hose releases 2 litres per hour (click photo to enlarge);

The fourth bed (tomatoes) where I used the inline 13mm drips;

And finally the fifth perennial bed;

After all the beds were completed, I got stuck into putting in 4mm lines with little taps for each of the fruit trees in pots.  I used the lasso method, where you use Drip Eze to make a circle around the tree all joined by a 4mm T.  This method give you about 4 drips per plant and cover the entire root zone.  This will make it easier to water the potted trees and I will still be able to isolate them if the need arises;

I gave Kim the grand tour, and tested each bed to make sure everything worked without any issues.  As I had reused old 13mm poly pipe that I had kept from old installations, I had missed one hole that I missed during installation, but quickly fixed it up with a bit of black silicone and a goof plug.  All sorted and each bed worked fine.  Then I turned it all off, because the beds were already damp from all the rain we had.

With all that finished, Ben helped me to planted up the empty bed with some mixed lettuce, spring onions, and celery seedlings which should all grow like crazy (which they did!), now that I can irrigate straight to the root zone.  I then showed Ben how it all worked by turning on one of the 100L water butts and turning off all beds except for the newly planted one.  He was absolutely fascinated and wanted me to check every single dripper to make sure that our plants were getting watered.  It was all working as designed, with both of us being quite thrilled to see it all working.  I then poured about 2 litres of worm wee into the 100L water butt we were using so that the plants would not suffer from transplant shock.  The beauty of using these small water butts is that you can add organic liquid fertiliser or soil conditioner and you will not contaminate all of the other water tanks/butts.  Also, by using the 100L water butt, you can water 2 beds at once and just let it all drain overnight until empty.  That way, you will not forget to turn off the tap if using your main tank. 

Over the course of an hour and a half, the Drip Eze bed only used 50L, which I thought was good, as each of the seedlings were well watered in.  I then turned that bed off, and let the remaining 50L water all the fruit trees and the rhubarb and loganberry bush.

All in all, the entire system of Drip Eze line, Moss Inline drips, T's, elbows, ratchet clamps, taps, filter and end stops cost me about A$160 in parts (I still have about $40 worth of bits that I didn't use), the 2 x 100L water butts were $59 each, with the 200L water butt and stand costing $110.  All 19mm and 13mm pipe was free because as I mentioned before, I used poly pipe from an old system.  I still have about 5 metres spare just in case I need to connect up the new tank that we are saving up for. 

It was great fun, and I have an overwhelming sense of accomplishment by doing it all myself.  Once I put my mind to it, there is I can achieve anything (well almost)!