Good morning GN! I hope everyone is well. I’m wanting to know if my air bleed valves should be installed at the beginning or ends of my runs? If there is anyone that would allow me to pick their brain on all things irrigation, that’d be great!
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Hey there Sam,
I’m the irrigation supervisor at a Canadian Licensed Producer. I could do my best to help you out! I’ve never used Foraflex unfortunately, but I’m sure I could still answer some questions for you.
How big is your grow? When you talk about air bleed valves, are you talking about releasing air out of your drip lines? You may have to help me out with what your set up looks like.
Cheers,
Jess
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Yo, Jess! Thanks for reaching out I’ll get straight to it lol. I had issues with my drip lines spitting and sputtering when the pump triggered. I purchased air bleed valves, but Ive become confused on whether they go before the first head or at the end of the run?
Pump: 6gpm/70psi
Line: 3/4" pvc
1 solenoid
3 runs @ 40’ each
5 - 8 spot heads per run feeding 40 spots (120 total). T’s on lines so shots are evenly distributed. 240 spots?
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Nice set up, Sam! Looks very orderly!
You’re going to want to set up your air bleed valve at a high point. If you have any low points in your irrigation lines, water will tend to sit there, causing an air lock between the high and low point. You’ll want to eliminate the air lock before the water reaches your plants.
Just to assure I understand fully, when you say “before the first head,” you mean before your first water release head? By “end of run” you mean the end of your lines?
Wouldn’t want to give you incorrect advice. 
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Thank you! I definitely likev things neat and straight. Yes ma’am, before there first water release head and end of run would be at the last water release head. The highest point would technically be the outlet on the left side of the pump at just around 5 feet. Should it go there before dropping to the ground?
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I’d say you’re pulling it off!
Judging by your photos, it seems like once your lines drop to the floor, they stay along the floor until they reach the tables, correct? Since it’s set up this way, you should be good to mount your air bleed valve at some point before your first head, so long as it is sitting vertically on top of the line.
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They do stay along the floor. However, from the water release head to the block there’s a roughly 8 inch l lift to the medium. Still ok? Lastly, should I have one bleed valve per row?
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You should be good!
If you install one per row, that will allow you to figure out if there’s a problem with one particular line, should something occur. If you know where your air lock is happening, I would start there. However, seeing as your lines aren’t too long, you shouldn’t need more than one at a spot where all the lines connect too - but again, that depends where your air lock is happening.
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Good pumps, I know them well. First question is what flow rate are you running the Floraflex bubblers?
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I had the 2 gph inserts in. Ive since changed them to the 6ph, but haven’t tested them. Totally new to irrigation and automation so I’m all ears lol.
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The first issue I see will be matching the flow rate of your irrigation to that positive displacement pump. If your irrigation flow rate is lower then your pump will short-cycle (rapid on/off behavior). This will fairly soon cause the pressure switch contacts to carbonize resulting in pump failure.
While you can replace the pressure switch with an external one to continue operation, I think it will be obvious that’s no way to run an airport - as is said.
To mitigate that you can insert a pressure tank, but preventing short cycling while filling the final 1/3 of that tank also presents similar short-cycling issues that requires a tricky plumbing circuit, but it’s do-able.
Also, all bubblers should have the same number of sites feeding from them to help ensure even flow distribution.
What is the total number of bubblers?
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In the room I’m working on currently, 15 heads, 120 sites. But, I planned on using t’s at each site to make sure the shots are evenly distributed. I’m not sure i understand anything above either, I’m sorry. Pressure tank?
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15 heads x 2 GPH = 30 GPH. Divide that by 60 minutes gives you a total flow of 0.5 GPM.
Your pump has an open flow (at no pressure) of 6 GPM.
This flow mismatch will cause your pump to rapidly cycle on/off (short-cycle), resulting in burnout of the internal pressure relay contacts leaving the pump non-operational after a relatively short period of time.
If you use the 20 GPH inserts you will be at a total of 5 GPM, meaning the above issue (short-cycling), will be greatly reduced and your pump will last longer, maybe even a full bloom cycle.
But, it will also impact how your plants experience the watering due to the different flow rates between 0.5 GPM and 5 GPM (at the bubbler/manifold - divided by the number of sites per bubbler).
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Ok, now i follow. So switching to the 20gph inserts will buy me a little time, but I’ll eventually need bigger pumps? What if I’m only feeding 2-3 times per day with 2 minute intervals?
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What is the total amount of water per plant you would like to deliver in each feed cycle?
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500 ml per feeding.
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1 liter = 0.26417 gallons / .5 (liters per feeding) = 0.132085 gallons per feeding.
6 GPM (flow) / 0.132085 GPF (volume) = 45.43 plants fed for one minute will each receive .5 liters.
120 plants / 45.43 plant capacity for desired volume / minute = 2.64 minute feeding will deliver .5 liters to 120 plants @ 6 GPM total flow.
With this formula you can match the flow of the pump by tuning the irrigation and feed-timing, while adjusting for plant count in order to prevent pump failure.
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Easy enough! I’ll get back with you folks if I have anymore questions… Which I’m sure I will. Thanks @Jess & @JoeGrow!
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Good luck!
Please note that’s a theoretical calculation. IRL implementation will add back pressure (expressed in feet of head) due to the friction of the tubing and interconnections, reducing both flow and pump overhead.
You’ll have to adjust feed times to compensate for enough volume and, perhaps add more plants (increase flow), to keep the pump happy.
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Best of luck, man! Let us know how it goes!
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