I have the complete 25 gallon sprayer and boom system from hunterworks and have been using it for about a year now. The pump is cycling because it is a pressure demand pump and thevalve you referred to in the tank return line is closed enough to build up pressure when the pump is running above the pressure limit switch built into the pump. That valve is used to regulate the spray pressure to the nozzles or to the wand, which ever you are using. The return line also provides "agitation" to the tank to help keep your spray material mixed with the water.</P>
The general concept is to keep the spray pressure as low as practical and still deliver the per acre volume of spray required. Keeping the pressure below 30 psi helps to reduce spray drift, by keeping the spray droplets large enough to "fall down" instead of "blowing away". Practice with plain water until you get the hang of adjusting the spray pressure and ground speed to achieve the proper spray concentration. </P>
In addition, I installed a few extra shutoff valves so I can spray with either boom only, center and one boom, or both booms and no center nozzles. For even more flexibility, you can get "plugs" for inside the nozzles to block offa single nozzleat a time. This allows me to spray narrow bands beside or behind the RTV. I also rigged up a mount for my GPS so I have a fairly accurate speedometer to more precisely control spray concentrations.</P>
The application chart with the instructions seems complicated at first, but once the light comes on, and you figure it out, you'll probably find that 11-12 gallons per acre is a good choice. That works out to 20 - 25 psi and 3.5 - 4.0 MPH. So if your spray diections show 1.5 - 2 quarts per acre, put 12 gallons of water in the sprayer adjust your return valve to get the desired working pressure based on the number of nozzles you are using, and then add the 1.5 - 2.0 quarts of spray material and you are ready to go. </P>
Drive at the desired speed and turn on the pump and you are spraying. At operating pressures below about 40 psi, the pump will run continuously and not cycle on and off.</P>
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