Now this issue is not going to applicable to those that grow acres of tobacco. but for the average back yard grower it might.
In my dessert climate, drip line irrigation is just about the only alternative I have.
This year I am going to try and grow 1651 plants in one lot. this will require 230 feet of 3/4 inch pvc pipe to run from the well to the tobacco patch. luckily it runs slightly down hill which will help preserve line pressure. Branching from that 3/4 inch main line will be as many as 13 1/2 inch drip lines containing 1651 1/2 GPH emitters.
I now have all the components but am very concerned my design will not work.
I have 40 P.S.I. and 27 GPM flow at the well. The system simply calculating at 1/2 GPH per emitter needs 825.5 GPH. In reality tests show that the emitters run closer to .75 GPH
We put 800 emitters into a 50 foot section of 1/2 inch drip line and tested it here at home with 900 GPH of flow and the pressure is unreal at 70 P.S.I. or more. At 800 emitters water nearly stopped flowing out of the end of the drip line when we removed the end cap. that means the system had used all of the water that can physically flow through a 1/2 inch line. Pressure had fallen to 0. The most emitters I can even run here at home in one line is about 750. adding branches will increase how many GPH can even flow through the system.
At the Tobacco patch I have the potential for 1620 GPH at 40 PSI. Can a 3/4 inch PVC line even carry that much water? According to information I have found online it can. But I am not sure that info is reliable. It appears to me they simply may have been crunching numbers rather than actually running water through pipes and testing it.
Also can 1 3/4 inch line supply enough water to 13 1/2 inch branches?
Finally at what point will the entire system not be able to supply enough water to 1651 1/2 GPH emitters?
AS I understand it these emitters require that the pressure remain at least 10PSI to even operate. My tests indicate otherwise. if there is water in the line even at 0 PSI these emitters will on average put out 1/2 GPH. THe emitters at the beginnign of the line actually where a bit over while the last ones where barely flowing. but the emitters in the middle measured at right at 1/2 GPH or a bit more. This tells me that by the time the last emitters where reached. there simply wasn't any water left. taking off the end cap confirmed this. There was barely a trickle of water coming out the end. Keep in mind this was a 900 GPH flow compared to the tobacco patch of 1620 GPH.
I am thinking my main concern is to provide more branches. this gives the water more paths to follow allowing more water per hour to reach emitters. I am just not certain how many branches.
13 sounds like to many, to many by far even. reducing the branches to just 4 is asking each branch to supply water to only 412 to 413 emitters. this is about half of what we tested a 1/2 inch line can supply.
Reducing branches to 2 causes each line to have to supply 825 or 826 emitters and my tests indicate that a 1/2 inch line cannot carry that much water. not even at fairly high pressure.
Anyway I hope to continue to document what I discover and just what answers I do find. In reality I intend to start one branch and run it until it stops flowing. at which time I will estimate where to cut it and then add another branch. So for example I may get 900 or 100 emitters into a single branch and find that I am running out of water. at which point I will evaluate just how short I need to make that branch to insure the second branch will receive enough water. I may be able to operate with as little as two branches.
I also suspect I will find that flow varies to much in longer branches. If this is so I may split into even more branches to even out the flow from every emitter.
I have done just about everything I can think of. otherwise it is now a matter of trial and error. At wost I have to run an extra 135 foot length of PVC and create a second "Zone". Not the end of the world. This causes the person watering the patch to have to go out after 2 hours, shut of one ball valve and open a second and then let that run for 2 hours.
In my dessert climate, drip line irrigation is just about the only alternative I have.
This year I am going to try and grow 1651 plants in one lot. this will require 230 feet of 3/4 inch pvc pipe to run from the well to the tobacco patch. luckily it runs slightly down hill which will help preserve line pressure. Branching from that 3/4 inch main line will be as many as 13 1/2 inch drip lines containing 1651 1/2 GPH emitters.
I now have all the components but am very concerned my design will not work.
I have 40 P.S.I. and 27 GPM flow at the well. The system simply calculating at 1/2 GPH per emitter needs 825.5 GPH. In reality tests show that the emitters run closer to .75 GPH
We put 800 emitters into a 50 foot section of 1/2 inch drip line and tested it here at home with 900 GPH of flow and the pressure is unreal at 70 P.S.I. or more. At 800 emitters water nearly stopped flowing out of the end of the drip line when we removed the end cap. that means the system had used all of the water that can physically flow through a 1/2 inch line. Pressure had fallen to 0. The most emitters I can even run here at home in one line is about 750. adding branches will increase how many GPH can even flow through the system.
At the Tobacco patch I have the potential for 1620 GPH at 40 PSI. Can a 3/4 inch PVC line even carry that much water? According to information I have found online it can. But I am not sure that info is reliable. It appears to me they simply may have been crunching numbers rather than actually running water through pipes and testing it.
Also can 1 3/4 inch line supply enough water to 13 1/2 inch branches?
Finally at what point will the entire system not be able to supply enough water to 1651 1/2 GPH emitters?
AS I understand it these emitters require that the pressure remain at least 10PSI to even operate. My tests indicate otherwise. if there is water in the line even at 0 PSI these emitters will on average put out 1/2 GPH. THe emitters at the beginnign of the line actually where a bit over while the last ones where barely flowing. but the emitters in the middle measured at right at 1/2 GPH or a bit more. This tells me that by the time the last emitters where reached. there simply wasn't any water left. taking off the end cap confirmed this. There was barely a trickle of water coming out the end. Keep in mind this was a 900 GPH flow compared to the tobacco patch of 1620 GPH.
I am thinking my main concern is to provide more branches. this gives the water more paths to follow allowing more water per hour to reach emitters. I am just not certain how many branches.
13 sounds like to many, to many by far even. reducing the branches to just 4 is asking each branch to supply water to only 412 to 413 emitters. this is about half of what we tested a 1/2 inch line can supply.
Reducing branches to 2 causes each line to have to supply 825 or 826 emitters and my tests indicate that a 1/2 inch line cannot carry that much water. not even at fairly high pressure.
Anyway I hope to continue to document what I discover and just what answers I do find. In reality I intend to start one branch and run it until it stops flowing. at which time I will estimate where to cut it and then add another branch. So for example I may get 900 or 100 emitters into a single branch and find that I am running out of water. at which point I will evaluate just how short I need to make that branch to insure the second branch will receive enough water. I may be able to operate with as little as two branches.
I also suspect I will find that flow varies to much in longer branches. If this is so I may split into even more branches to even out the flow from every emitter.
I have done just about everything I can think of. otherwise it is now a matter of trial and error. At wost I have to run an extra 135 foot length of PVC and create a second "Zone". Not the end of the world. This causes the person watering the patch to have to go out after 2 hours, shut of one ball valve and open a second and then let that run for 2 hours.