A tank machine needs refilling, while a plumbed-in machine needs a connection. Which suits your office better?
A tank machine is easier to set up and can be moved, but it needs daily refilling. A plumbed-in machine draws water from the supply, which is convenient for heavy use, but it needs a connection, often a filter, and professional installation.
When to choose a tank
In small offices, in rented spaces without a water connection, and where the machine may move around.
When to choose a water line
When drink volume is high and nobody wants to carry water every day. A water line usually needs building management approval and installation per the manufacturer's guide. Many office coffee vending machines (publisher's site) work this way.
Hygiene either way
Rinse the tank at every refill. With a water line, keep up with filter changes and checkups.
FAQ
Can any machine be plumbed in? No. Only models designed for it by the manufacturer.
Does a water line need a drain? Some do. Check the specs.