Short answer: a commercial kitchen needs a three-compartment warewashing sink, at least one dedicated handwashing sink, and, if it runs a high-temp dish machine, a booster heater to hit the sanitizing rinse temperature. First-timers routinely under-plumb, assume a dish machine cancels the three-comp sink, or forget the booster. Each is a fixed cost the health inspector checks. Here is what the FDA Food Code actually requires.
The three-compartment sink (a dish machine does not replace it)
FDA Food Code 2022, §4-301.12(A):
"Except as specified in (C) of this section, a sink with at least 3 compartments shall be provided for manually washing, rinsing, and sanitizing equipment and utensils."
The three-comp sink is the manual wash-rinse-sanitize line, and it is required whether or not you also install a dish machine. Buyers who plan around "the dish machine handles it" get sent back to add plumbing before opening.
A dedicated handwashing sink (separate from everything else)
§5-203.11(A) requires a handwashing sink that is not the prep sink or a warewashing compartment:
"at least 1 handwashing sink, a number of handwashing sinks necessary for their convenient use by employees in areas specified under 5-204.11, and not fewer than the number of handwashing sinks required by law shall be provided."
So the minimum sink count is three fixtures doing three different jobs: the three-comp warewashing sink, a handwashing sink, and (in most builds) a separate food-prep sink. Under-counting here is one of the most common first-open failures.
The dish machine and its hidden booster heater
If you go high-temp (hot-water sanitizing) rather than low-temp (chemical), the final rinse has to reach a real temperature. §4-501.112(A):
"in a mechanical operation, the temperature of the fresh hot water sanitizing rinse as it enters the manifold may not be more than 90°C (194°F), or less than: (1) For a stationary rack, single temperature machine, 74°C (165°F); or (2) For all other machines, 82°C (180°F)."
Hitting a 180°F final rinse almost always means a booster heater — an extra piece of equipment and a real electrical load buyers forget to budget. A low-temp chemical-sanitizing machine avoids the booster but adds ongoing sanitizer cost. That trade-off is worth pricing before you buy the machine, not after.
Match a used dish machine (high-temp vs low-temp, booster included or not) against its documented failure modes and parts before you buy: browse the model records. And confirm the equipment itself is certified before it goes in — see why you can't use a home fridge in a commercial kitchen.