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LemkeLawns
08-13-2008, 09:55 AM
guys, I am working on a new install and was curious as to when a person needs to step down in pipe size. I'm not necessarily looking for a specific case scenario but rather a way to calculate when to step down and how drastic of step down. Any help would be greatly appreciated!!

Dripit good
08-13-2008, 10:01 AM
From what size, to what size?

LemkeLawns
08-13-2008, 10:09 AM
is there a general formula used to determine when to step down?? Id like to apply the formula to different situations in the future so im not wasting every ones time by saying im using pipe size A when should i switch to size B and im going X distance with Y psi and Z flow

Waterit
08-13-2008, 10:10 AM
Look in rear of Rainbird catalog for pipe-sizing charts, then add up your GPM as you add heads to zone.

Or take a class at your local distributor to get some knowledge before you start installing. Your question is very basic knowledge for any installer, makes me wonder what else you don't know about this game. Not being nasty (well, a little), just saying that like anything else, having a clue about what you're doing goes a long way towards doing it well. And that's what it's all about.

Wet_Boots
08-13-2008, 10:16 AM
If you are going to step down from one-inch to 3/4-inch pipe in a line of heads, a good general rule is that you can feed two 3-gpm rotors from 3/4 pipe without excess pressure loss.

evergreensolutions
08-13-2008, 10:20 AM
IN GENERAL......GPM for all heads downline dictates pipe size. You do not want to exceed 5 fps for the given pipe size or you increase chances of water hammer. Flow Charts are your best friend when designing a system. "General Rules" are different for everyone. Someone might be comfortable with a little more velocity than me. Comes from experience.

Dripit good
08-13-2008, 10:22 AM
Waterit nailed it. Take a basic course and refer to the pipe charts. My sugestion is don't reduce your laterals less than 1". Too many parts to buy and stock for no real good reason.

LemkeLawns
08-13-2008, 11:20 AM
thanks everyone! Ill b the first to say that im ignorant when it comes to irrigation. I see it as there isnt any harm in asking before a project, but there is a ton of extra work if a system that is put in wrong and has to be redesigned and reworked. I have learned a ton from my rainbird and hunter catalogs over the last week including info about nozzle sizing, psi loss, under zoning systems, and the list goes on. thanks guys

Waterit
08-13-2008, 12:23 PM
thanks everyone! Ill b the first to say that im ignorant when it comes to irrigation. I see it as there isnt any harm in asking before a project, but there is a ton of extra work if a system that is put in wrong and has to be redesigned and reworked. I have learned a ton from my rainbird and hunter catalogs over the last week including info about nozzle sizing, psi loss, under zoning systems, and the list goes on. thanks guys

You're on the right track, you recognize that there are things you don't know and seek knowledge. Journey on, Grasshopper!

LemkeLawns
08-13-2008, 10:56 PM
The reason I decided to start installing irrigation was b/c it cost me $360 to replace a golf head that we hit on a football field we mow. I worked under an IA member at a local university and knew that if the installer knew what the f he was doing, his heads wouldnt have been set above grade and sheered off with by my mower. Then this week I ran into his work again on a volunteer install job at a sports complex. He shows up and starts rattling off theories of what a person could do at the site and that there are 100 different ways this system could be installed.... he took absolutely no measurements, didnt check what kind of flow or psi the booster pump is putting out. There is an existing system on a baseball field and two additional practice fields will be ran off this same pump. I thought this would be an excellent time to increase my knowledge on psi and friction loss. I have found that this guy's design will yield a velocity greater than 5ft/s in the main line and in order to have 1 inch of precip. the system will need to run for 32 hrs. The system is capable of 77 gpm and is measuring 70 psi on the baseball field. This guy will only be using about 35 gpm per zone on the new system. When I mentioned that he had absolutely no clue on what the pump was putting out, he replied "it works over there so it will work over here.":wall

bicmudpuppy
08-13-2008, 11:01 PM
The reason I decided to start installing irrigation was b/c it cost me $360 to replace a golf head that we hit on a football field we mow. I worked under an IA member at a local university and knew that if the installer knew what the f he was doing, his heads wouldnt have been set above grade and sheered off with by my mower. Then this week I ran into his work again on a volunteer install job at a sports complex. He shows up and starts rattling off theories of what a person could do at the site and that there are 100 different ways this system could be installed.... he took absolutely no measurements, didnt check what kind of flow or psi the booster pump is putting out. There is an existing system on a baseball field and two additional practice fields will be ran off this same pump. I thought this would be an excellent time to increase my knowledge on psi and friction loss. I have found that this guy's design will yield a velocity greater than 5ft/s in the main line and in order to have 1 inch of precip. the system will need to run for 32 hrs. The system is capable of 77 gpm and is measuring 70 psi on the baseball field. This guy will only be using about 35 gpm per zone on the new system. When I mentioned that he had absolutely no clue on what the pump was putting out, he replied "it works over there so it will work over here.":wall

Welcome to our world. Hope you stay in front of the curve long enough to make it.

Waterit
08-14-2008, 12:14 AM
When I mentioned that he had absolutely no clue, he replied "it works over there so it will work over here.":wall

Classic! You are already way ahead of him, use that guy as an example of how NOT to do it.

bicmudpuppy
08-14-2008, 12:35 AM
I will get some gasps from this (I'm rarely charitable w/ the ignorant, but your fighting stupid and that means you get help), but feel out the irrigation parts house of your choice. Find an adequate designer there and ask him to spec the job for your. He might even explain the final design for you (esp. if you get to install it). This would mean you could provide a professional presentation from a hydraulic stand point w/o waiting to catch up on the learning curve. (I suggest this short cut to save time, NOT as a permanent solution)