How to increase psi in my gravity irrigation system?

[MossRoad]

How much of a total drop in elevation is in the 6" pipe?

 

[plowhog]

You could put a pressure regulator on the system down at the outflow end not to exceed 45psi.

I did shop for these. the 2 1/2 inch size has limited selection. I saw some for over $1000 dollars ouch.

Btw I believe higher velocity at the 6 inch outflow is why it seems the same 45 gpm throughput with only 1/4 cross section of the pipe full, even though the pipe cross section at the intake is nearly full.

 

[plowhog]

How much of a total drop in elevation is in the 6" pipe?

I don't know. It runs through a forest on a very shallow grade so it is not easy to measure. I probably need to measure it somehow as I probably need to find a spot where the six inch pipe is 24 feet above it's outlet. It would be about that location where joining the two pipes would add 10 psi.

 

[jmc]

plowhog, I think you need to solve this 6 inch mystery first. Have you considered root infiltration somewhere along the 6 inch pipe? An old pipe being heaved may have openings, or a separation between pipe lengths. Around here, sewer pipes are famous for this, to the point of complete blockage. Apparently, roots don't need much of an opening. Interesting project though.

 

[plowhog]

plowhog, I think you need to solve this 6 inch mystery first. Have you considered root infiltration somewhere along the 6 inch pipe? An old pipe being heaved may have openings, or a separation between pipe lengths. Around here, sewer pipes are famous for this, to the point of complete blockage. Apparently, roots don't need much of an opening. Interesting project though.

I drilled into the top of the pipe in the two locations where I added air release valves. I examined the pipe inside there for mud or debris. It was clean.

 

[shooterdon]

It may be easier to add more sprinkler heads or ones that will work with 35 PSI.

 

[MossRoad]

I don't know. It runs through a forest on a very shallow grade so it is not easy to measure. I probably need to measure it somehow as I probably need to find a spot where the six inch pipe is 24 feet above it's outlet. It would be about that location where joining the two pipes would add 10 psi.

A GPS would get you close in elevation estimation.

 

[metalbender]

Old issues of Mother Earth News might have the answer. Hydraulic ram, water powered pump.

 

[jaxs]

I don't know. It runs through a forest on a very shallow grade so it is not easy to measure. I probably need to measure it somehow as I probably need to find a spot where the six inch pipe is 24 feet above it's outlet. It would be about that location where joining the two pipes would add 10 psi.

Doesn't work like that. As you have seen,friction is already overcomeing head in 6" pipe because pipe start's out full at intake but is only 1/2 full at discharge. Reducing size of pipe up-hill from present discharge will only reduce GPM. "IF" 6" pipe is capiable of flowing 45GPM at 45 PSI (which I seriously doubt) ,connecting 6 to 2.5 at existing water box will do much better. The only way I can see to gain head is a tank 20' higher than box and where water box is now. A solar pump capiable of 20' head isn't expensive but the GPM isn't much. Without doing any math,the pump would run for hours and tank would need to be much larger than you probibly can afford. 45GPM is a large volume,esp at 45PSI. The elevated tank might be viable if you can run fewer sprinklers at same time. Commercial growers in the valley use flood irrigation for their crops,can you do that with at least some of yours? I keep coming back to less GPM for and extended time being the solution.

 

[4570Man]

Doesn't work like that. As you have seen,friction is already overcomeing head in 6" pipe because pipe start's out full at intake but is only 1/2 full at discharge. Reducing size of pipe up-hill from present discharge will only reduce GPM. "IF" 6" pipe is capiable of flowing 45GPM at 45 PSI (which I seriously doubt) ,connecting 6 to 2.5 at existing water box will do much better. The only way I can see to gain head is a tank 20' higher than box and where water box is now. A solar pump capiable of 20' head isn't expensive but the GPM isn't much. Without doing any math,the pump would run for hours and tank would need to be much larger than you probibly can afford. 45GPM is a large volume,esp at 45PSI. The elevated tank might be viable if you can run fewer sprinklers at same time. Commercial growers in the valley use flood irrigation for their crops,can you do that with at least some of yours? I keep coming back to less GPM for and extended time being the solution.

Why do you doubt 6” pipe is flowing 45 GPM? It is capable of way more which would explain it being only 1/4 full. Even if the 6” pipe is 4” pipe it’s still easily doable. A good water hose can probably push 1/3 that much.