additional thoughts on airlocks

I harvest rainwater and when I need to irrigate I pump the water to a tank at the top of a hill (right hand tank in the picture) and use gravity to move the water from the tank to its final destination.  See my description of the system and airlocks at airlock problems

I use a 1.25″ pipe to take the water from the top of the hill to the base of the hill and then I use a manifold to direct the water into four 1″ pipes, three of which irrigate the orchard with positioned bubblers and the fourth goes to the vegetable growing area where I hand water with a hose.



Over the years as my patience with air bubble delays diminished, my progress towards a solution increased.

a)  In the beginning I opened the valve to the hose at C and waited for the trickle of water to slowly increase in volume as some but not all of the air bubbles were expelled by the water pressure.

b)  Then I made a tee at C with 2 water valves, one to the hose and the other to a short length of pipe.  I would open first the valve to the short length of pipe and the water would flow more quickly since it did not have to go through the hose.  With the water flowing faster, the blockages cleared quicker.  It sounded like a train gradually gaining speed.

c)  I discovered that if I opened and then quickly closed the valve to the short pipe it increased turbulence in the downhill pipe since the water coming down backed up, and then if I quickly opened the valve again the water appeared to come through with more pressure and bring more air bubbles with it.

d)  But this all took time so I developed a smarter approach.  Before starting with C, I went to the manifold at B and opened a spare valve.  Now the water rushed out with quick stabbing pauses as the air in the 1.25″ pipe was ejected.  It took very little time to clear all the air in the pipe from A to B because this pipe was at a steeper incline and larger diameter than the pipe B to C.  Then clearing the 1″ pipe from B to C was much quicker.

e)  And finally, to avoid air blockages all together I made my final change.  I had gate valves at the manifold and some trickled water in the fully closed position so overnight the pipe from A to B lost water.  I replaced the gate valves with ball valves and eliminated all leaks so the full length from A to B and B to C was full of water with no air pockets before I began irrigating.  The trick was to stop watering before the tank at the top of the hill emptied.

These procedures have minimized the inconvenience of air pockets in my gravity fed irrigation setup.

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