spray head questions
I'll try to shed some light on the confusion.
Size of pop up is most usually determined by the type of turf you are planning on growing, and consequently, the length you have it cut. You want the spray to clear the grass. Here, we have cooh season grasses, and most are cut to a height of 2 - 2 1/2 inch, so 4 inch bodies are all that is needed. Here, the 6 in cost quite a bit more than 4 inch. The top of the body is mounted at grade.
Nozzel selection should be based on your design, coverage of area and percipitation rate. VAN's have a reputation for clogging, although this has not been an issue for me. It is hard to match their precipitation rates with other types of sprayheads, and even with themselves in the same zone, since they put out the same amount of water independent of the arc..smaller arc settings use the same amount of water over the same time as a VAN set at a larger arc, making the one set at the smaller arc overwater,or the one at the larger arc underwater. I use them when nothing else will work, such as when a larger pattern will overspraying on a critical area. You did not indicate the layout or size of your area(s). I usually design with head to head coverage to insure the close in areas receive adequate precip.
There is nothing special about sprays. Basically, they use lower pressures (somewhat) and are spaced closer together than rotors (yes, before someone jumps on me, I know there are exceptions). Start your design along a critical edge that you do not want oversprayed ( perhaps the side of a building, a driveway, or a fence - since the water will leave unsightly stains, or creat a slippery walk. Index off this border. Small areas lend thjemselves to peripheral placements. Sprays tend to deliver more water to a smaller area than rotors, so your run times are shorter than for rotor zones. You will read about MP rotors, which operate with much lower volumes (flow), but otherwise are similar to sprays and rotors.
Lastly, depending on your location, SAM's need to be blown out before freezing, or they are TOAST. Their enclosed check valve make them hard to gravity drain, and then the retained water freezes....broken bodies. I generally try to avoid them, unless my zone includes a low head, which when the zone is turned off, has all the water in the lateral drain flow out around it, causing excessive moisture. I always use PRS heads, it takes the worry out of designs for the most part.
Hope that sheds light more than create more problems for you. Feel free to write back with other questions or clarifications.
Jeff