&lt;p&gt;In case of power operated sprayer horizontal triplex pump (HTP) is used as pressure generating unit. In the fields, at headland spraying is not necessary. At such places spray has to be stopped and the pump should run idle. However, there is some load on the pump, which may cause damage to the pump and wastage of power. This problem could not be tackled by the control valve assembly of tractor-mounted sprayer. Therefore, new unloader valve was designed and fabricated to solve the problem. It was tested in the laboratory. The unloading pressure range of the unloader valve was found to be 10 to 28 g/cm2. The power required during loading and unloading conditions was measured while opening and closing the discharge lines. The power required during loading condition was found to be 0.22 to 0.34 hp at pressures of 10 to 28 kg/ cm2 and at pump speed of 910 to 770 rpm. The power required during unloading condition was 0.11 hp. The power saved with the use unloader valve during loading and unloading conditions was found to be 0.11 to 0.23 hp at pressures of 10 to28 kg/ cm2 and at pump speed of 910 to 770 rpm. The power saved was nearly 50% of required power. As the unloader valve bypasses the whole spray liquid allowing the pump to run at idle speed, it saves the power and pump from damage.&lt;/p&gt;
