The Solo backpack sprayer is equipped with a built-in regulator to control output pressure. This regulator is operator adjustable. Make adjustments prior to filling tank. To adjust the regulator, remove the tank cap and the filter basket. Look inside the spray tank; you will see the top of the regulator. There are 4 fingers on the regulator knob. The finger farthest to the right is #1; to the left is #4. They are numbered 1, 2, 3, 4. 1 = 15 psi, 2 = 30 psi, 3 = 45 psi, 4 = 60 psi. The higher the pressure, the more chemical applied from the sprayer in a given amount of time, but the droplets will be smaller with more drift. If the spray pressure must be changed, excess pressure in the pressure cylinder must be released back into the tank through the spray tube. To adjust, push down on the knob and rotate to align the desired number with the alignment pin. If a spray pressure exceeding 60 psi (4 bar) is required, first release the excess pressure and then replace the adjustment piece with the optional plug (#4200215). The plug should only be used on piston pump sprayers.

Please note: the maximum pressure the models 425, 435 are capable of is 90 psi and the 474, 475, 476 and 485 models is 60 psi. For operating the 425, 435 at higher than 60 psi, the pressure control valve must be removed and replaced with an optional plug (#4200215) (see item B)