After you have planned and marked your valve placement, you can plan your irrigation pipe layout. You will want to use a direct route from the main shut-off to the front and backyard sprinkler valves. Your main sprinkler line should be one size larger than your main water supply line.
There are two types of irrigation lines: header and lateral. Header lines should not be smaller than one inch and attach to the main sprinkler pipe and supply lateral lines with water. Sprinkler heads should not be attached to header irrigation lines. Lateral lines branch off from the header lines and supply water to lawn sprinklers. They should not be smaller than 3/4 inch.
Map out your header lines directly from your valve manifolds. In your drawing, the lateral lines should intersect with the header lines and should branch out and not in a circular pattern.
Once your sprinkler lines have been mapped, you can decide on a sprinkler timer location. Select an area near a power source and that is easy to access. If the location is outside, be sure to purchase an automatic water timer that has a weather-resistant box, outdoor mounting materials and even a lock. If the sprinkler timer location is inside, be sure you have mounting hardware for it.
On your graph, mark the water timer location. From that location, plan a direct route for electrical wire to connect from the watering timer to the front and backyard valve manifolds.
Your custom sprinkler system design is now complete! With your graph and gathered information, you can purchase all the supplies you need to install your do-it-yourself sprinkler system.