Search a ratio chart for your hydrominder model. If it is a self serve it is likely a 506 or 511. Ratios with the screw in tips vary from 4:1 to 240:1. This is a rough guideline only as mentioned as there are several variables. The biggest one is the viscosity of the product. For example you may have to use a tip that would draw water at 48:1 to get a true 100:1 ratio with a soap because of the product's thickness. Find a rough starting point and work in the chart direction towards the desired performance (color, visual appeal, strength) of your product.