Thank you for taking the time to share your feedback. We are sorry to hear about the issues you are experiencing with your 24V Backpack Sprayer. Leaking at the base around the screw bosses can sometimes occur if the tank has developed small stress cracks, was over-tightened during assembly, or experienced pressure buildup beyond its intended capacity. We recommend first ensuring all screws and connections are snug (but not overtightened), and inspecting the tank for any visible hairline cracks or deformation, especially near the base. It may also help to confirm that the unit is not being overfilled, as exceeding the recommended fill level can increase internal pressure and contribute to leaking. Regarding the tank capacity, while the unit is designed with a nominal 4-gallon rating, usable capacity can sometimes appear slightly lower due to internal components, fill markings, or the need to leave space for proper pressurization and safe operation. For mixing accuracy, we recommend using the fill markings inside the tank or pre-measuring liquids externally before adding them. If the leaking persists or the tank appears compromised, this would not be expected performance. We encourage you to reach out to Greenworks Customer Success at 1-888-909-6757 or via chat at www.greenworkstools.com so the team can review your unit and assist with a resolution under warranty if applicable.