If there is no fertilizer flowing after a few minutes of operation, shut off the system, wait a few moments and restart it. When starting, the system water flows into the tank until it is totally full and at the same pressure as the watering system. Fertilizer will begin to flow once this has happened. This can take a minute or more when the tank is refilling. Remember, the tank must be completely full of fluid before fertilizer starts to flow. Fertilizer with dark dye coloring will look darker flowing through the clear tubing than lighter colored fertilizers, even though they are feeding at the same rate. With low flow systems the fertilizer flowing through the tubing may have less color because the system automatically adjusts the fertilizer ratio to the water going through the system. Dry fertilizers can take longer to begin flowing than liquid fertilizers because they need to dissolve first. If you are using tubing valves, make sure they are in the "on" position. The green fitting on the cap is connected to the clear, downstream tube, while the blue fitting on the cap is connected to the black, upstream tubing.