A fire apparatus includes a fluid delivery system having a water circuit, an agent circuit, and a ratio controller. The water circuit includes a water pump configured to pump water from a water source through the water circuit. The agent circuit includes an agent tank configured to store an agent, an agent pump configured to pump the agent through the agent circuit, and an agent metering valve positioned to variably restrict a flow of the agent therethrough. The ratio controller is positioned to receive the water and the agent. The ratio controller is configured to provide an agent-water solution to one or more outlets. The agent metering valve is a self-adjusting metering valve having a valve controller configured to adjust at least one of an orifice size and a valve position based on a water flow rate entering the ratio controller and a preselected agent-to-water ratio for the agent-water solution.