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Tuesday, April 9th 2013, 9:48am

Main Line Diameter

Hello all,

This summer I will be installing an irrigation system my self. I have been purchasing parts this past winter and I am now ready to buy the pipe for the main line, problem is, I'm having difficulty figuring out what diameter to use.

I have municiple water, a 1" copper service line and a 1" meter; the system holds between 47-50 psi and produces about 8 gpm. There will be 7 zones and 42 total sprinkler heads. I live in southeast Michigan so I will be using poly pipe since ground freezing is inevitable.

Any help of advice regarding diameter will be helpful. Thanks in advance.


Active Member

Posts: 29

Location: Longview, Texas


Tuesday, April 9th 2013, 11:21pm

Im not an expert in the sprinkler field, but your question is basic one.

Your mainline and lateral size will depend on the Final Deisgn. The deisgn includes how much pressure
(both static and dynamic) you have, how much losses you have and how much GPM each zone will require
etc. So there is no answer to the question until the design is known. As a sort of rule of thumb, your main will be at least the same as your main line from the water supply. However there are exceptions to that rule.

I highly recommend you read and then read again the irrigation tutorial. Everything you could possibly need to know and learn to design and install your own system in a normal lawn is there.

(you will prolly have to copy/ paste this link into your browser to make it work). This is not a boring read either. The guy wrote it in a manner which is both entertaining and understandable by a novice like me.

I designed and installed my own system solely by studying the irrigation tutorial over and over until I understood what I was doing so that I was sure I was doing it right.

As a FYI, if you did the bucket test and came up with the 7 gpm from the hose bib, then most likely that is wrong. Same thing happened to me... I retested once I tapped into my 1 inch main and lo and behold, I have 18 GPM available instead of 7 or 8 that came out of the bib.

By the way, I just finished my sprinkler system this past weekend and my sprinkler system works wonderfully. I could not be happier and my neighbors are impressed too. 8) I could not have done it though without the tutorial by Mr. Stryker. He Rocks!

hope this helps, and good luck.

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