I've wanted a lawn sprayer for years. The sprayers I've found in stores or on the Internet are all mounted on little trailers and have two or three sprayer nozzles that are located at least two feet above the ground. Last spring, I borrowed one of these sprayer trailers from my brother-in-law and found it lacking for several reasons. Sprayer nozzles two feet above the ground combined with our normally brisk wind allowed the spray to drift to places and plants I didn't want sprayed. I also had trouble maneuvering the trailer hooked behind my riding lawn mower.
Given last spring's lawn spraying experience, I decided this year I wanted a sprayer that was mounted on my mower, not on a trailer, and a sprayer that had spray nozzles much closer to the ground. I rehabilitated an old sprayer I had retired from spraying our row of pine trees before they got too tall and before I found that bug zappers did a better job of protecting the trees from pine tip moths. I'd already set up this sprayer to ride on a hitch cargo carrier. An Internet search led me to a cheap four nozzle spray boom that I purchased from Amazon.com. I replaced all the hoses and the input check valve. Once everything was assembled, I experimented with nozzle height. I quickly concluded that the 80 degree spray tips that came with the boom were inadequate at the height I wanted, but these were easily replaced with four 140 degree deflector type tips from Atwoods. Here's a photo of my lawn spray rig and the resultant spray pattern.
Note the nice even six foot plus spray pattern. Also note that while I was at it I mounted two hose quick disconnects to make assembly easier and to allow me to quickly add a spot sprayer to the rig.
Update: The sprayer worked well. It's now disassembled and stored. I got good coverage in a strong wind, killing most of the early fescue. I liked everything about the operation except having the sprayer boom behind me and having t0 continuely look back. Next year, I plan to rig the spray boom across the front of the mower. I'll also add a convienent liquid valve to shut off the spray instead of relying on the pump electrical switch. That should avoid unwanted spraying and dribbling.