Jess Stryker's Landscape Sprinkler Design Tutorial Step #4  Sprinkler Pipe Layout

Now that you have the valve zones shown on your drawing it's easy to add the pipes going to the sprinklers. Start with one of the valves and draw a line to the closest sprinkler in the corresponding valve zone. Then draw a line to the next sprinkler in the valve zone, and the next, etc. Some helpful tips:

• For small residential sprinkler systems try using a different color pencil for the pipes in each valve zone. This will make your plan easier to understand.

• Where possible you can minimize the amount of trenching by placing pipes together in the same trench. Show these pipes side-by-side on your plan.

• Run the pipes as efficiently as possible. In most cases this will be the shortest possible route between each sprinkler, but this is where you need to just look at your plan and think about it a bit. You may find it easier to run one pipe down the center of an area and spur off of it to each sprinkler. Or it may be easier to split the piping with one pipe going to half the sprinklers and the other going to the other half. Some may want to minimize the number of trenches, even if it means using a less direct route for the pipe so two pipes can share a trench. There is no set routing pattern that you must use for the pipe. If for some odd reason you need to route the pipe all the way around the yard to get to a sprinkler only a few feet away from where you started that's O.K. Try several different layouts until you find one that YOU like, that fits YOUR needs.

• Show no more than 2 pipes connecting to a sprinkler head-- one coming into the sprinkler, and one going out. If you need to branch off from the sprinkler with a 3rd pipe, show the 3rd pipe branching off of the 1st pipe just before it goes into the sprinkler. There is no part made that will allow 3 pipes to connect together at a sprinkler head location. Study the sample drawing below for examples.
• Try to avoid running pipes within 5 or 6 feet of existing trees. The roots will make it hard to dig trenches for the pipe. With really big trees I try to keep the trenches out from under the canopy of the tree. If I need a sprinkler in that area I run the pipe around the perimeter then go straight in toward the trunk to the sprinkler head. Of course, this may not always be possible. Sometimes you will just have to go through an area with tree roots.

Splitting flows or splitting hairs? You may have heard that the flow from each valve should always be split just after the valve, with one pipe going to half the sprinklers and the other pipe going to the other half. The reasoning is that this "balances" the system. Good designers can balance the flows without resorting to this old method. You are well on your way to becoming a good irrigation designer, so you can forget about such amateurish methods! Route the pipe however you want to route it!

Draw the lateral pipes between the sprinkers and the valves. If you haven't drawn the mainline pipe from the valves to the water source, draw it now also.

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Determine Flows in Pipes:

In order to determine the pipe size we need to know the flow rate (GPM) of the water in the pipe. Calculating the water flow in each section of pipe is extremely easy, but many people have problems with it. They try to make it too complicated. Just observe the layout of the sprinklers and ask yourself which sprinklers are DOWNSTREAM of this pipe section. It's simple logic, the water must flow through this pipe to reach the sprinklers downstream. Add the total GPM of those sprinklers together and you have the GPM that will be flowing through the pipe.

1. Start at the valve. The first section of pipe goes from the valve to the first sprinkler head. All the water for every sprinkler operated by this valve must flow through this section of pipe to get from the valve to the sprinklers, right? So the flow in GPM for this section of pipe is the total of the GPM of all the sprinklers operated by the valve added together.

2. The remaining sections are just as easy. The total flow through each section of pipe is the same as the total GPM of all the sprinklers downstream from that pipe section. Add together the individual GPMs for each of those sprinklers to get the flow through the pipe section. Don't make it harder than it is! If you have a short spur pipe leading off to a single head, then only the water going to that head will pass through the spur pipe! So the flow for the spur pipe is the same as the GPM of that single head. Carefully study the sample design below.

Using a pencil, write the flow for each pipe section down on your drawing next to the pipe.

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