The DS-1800Z does come with a filter so you don't need to purchase the 3-pack separately. I would recommend purchasing the 3-pack at the same time so you do not have to reorder filters so soon. This helps save on shipping costs.
The DS-1800Z is located here:
PUR DS-1800Z Water Filter Dispenser and PUR DS1800Z Water Filters
Thank you,
WaterFilters.NET