None of the water vending units that we produce include reverse osmosis water filtration.

There is a very sound reason for not doing so. Generally, the only times this type of treatment is needed is when the total dissolved solids (TDS) count is above 500 parts per million. If the vending water machine is to be hooked up to a water source that has already been treated by a public utility or water treatment plant, then the amount of TDS has already been reduced below this threshold.