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Supreme Member

Posts: 456

Location: USA


Monday, December 31st 2001, 12:32pm

Mainline Pipe size

Do I use a 1'' PVC Pipe for my mainline? I have a 3/4 inche service line and a 5/8'' Water meter. If not what is the correct size?

Posts: 60

Location: USA


Thursday, January 3rd 2002, 5:53am

<b>The quick answer is:</b>
Yes use a 1" mainline and connect it as close to the water meter as possible. You want to tie into the water meter and not off the side of your house so that you can keep your pressure loss to a minimum and make sure you supply the sprinkler system with the maximum amount of water (rate) at the maximum available pressure. Your house may be feed with a 3/4" mainline, but you do noy want to use 3/4" for your sprinkler system mainline. A 5/8" meter is very common in neighborhoods and you can pull up to 14 gpm (lower max) - 18gpm (highest max) of water. Do not ever exceed the 18 gpm and you should try to stay down closer to the 14 gpm if possible.
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Posts: 60

Location: USA


Thursday, January 3rd 2002, 6:27am

<b>Now for a more detailed explaination:</b>
The quick crash course on installing a sprinkler system would give you the following rules of thumb:
1. Always tap into the water supply line to feed the sprinkler system as close to the water meter as possible.
2. Always install a ball valve (highly recommend a PVC ball valve) underground in a valve box close to were you tapped into the water supply line. this will allow you to turn of the water to the spprinkler system without turning off the water to the house if you need to in the future.
3. Always use big enough mainline pipe from the water meter to the backflow prevention device , then to each zone (section) valve, and then down the middle of each zone (section) that feeds the sprinklers. If you undersize the pipe you will have significant water pressure problems. You can determine which size pipe to use by looking at the friction loss charts found on the following link:
or this link on Rain Bird's website:
To use the either chart, you find the chart for the type of pipe you are using and you find the size pipe you think you need and then see what the water velocity through the pipe will be when you try to supply water to the zone in your sprinkler system that will use the most water (most gpm). To calculate the gpm for a zone, you add up the number of sprinkler heads on each zone and how much water each head uses based on the nozzle you will be using with the various sprinkler heads. Once you total the number of gpm's your largest zone will have (should be under 18 gpm's since your water meter will not handle any more gpm's), you look at the chart.
Using the chart determine what the velocity in the pipe will be for the number of gpm's you want to put through the size pipe you have chosen. *** Important*** If the velocity exceeds 5 feet per second, you must use the next size bigger pipe until the velocity is lees than 5 feet per second. This will tell you the pipe size you need as the mainline.
After you begin to branch off the mainline and supply sprinkler heads you can use smaller pipe since the water through the branched pipe is much less than the mainline pipe.

*** To get a good understanding of how to design and pipe your sprinkler system please use the following link to go through a step by step tutorial or summary (includes great pictures) of how to design and install a sprinkler system:

You can also use our charts and technical info sheets found in our Technical Data section of our website to assist you in the design and installation of your sprinkler system:

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