Size the machine for your busiest hour: undercounter units suit bars and small cafés, door-type machines suit most full-service restaurants, and conveyors suit high-volume and institutional kitchens. Then choose high-temperature sanitizing, which needs a booster heater and more power, or low-temperature chemical sanitizing, which costs less up front but uses sanitizer every cycle.
Key takeaways
- Choose the machine type by racks per hour at peak, not by the number of seats alone.
- High-temperature machines sanitize with a very hot final rinse and usually need a booster heater; low-temperature machines sanitize with a chemical and run cooler.
- Hard water shortens a dishwasher's life; ask about water treatment before installation.
- The dish tables and the direction of flow matter as much as the machine itself.
- Confirm voltage, phase, water supply, drain and ventilation requirements from the spec sheet before ordering.
The main types of commercial dishwasher
Commercial dishwashers wash a rack, not a load. Most North American machines take the standard dish rack of about 20 by 20 inches (roughly 500 mm square), and the difference between types is how many racks they can turn over in an hour and how the racks get in and out.
- Undercounter: fits under a counter like a household machine and is loaded from the front, one rack at a time. Suits bars, cafés, small restaurants and glass washing.
- Door-type, also called hood-type or pass-through: a stand-alone machine with a lifting door, fed from a dish table on one side and emptied onto a table on the other. The usual choice for full-service restaurants.
- Conveyor, or rack conveyor: racks are pushed through wash, rinse and sanitize zones by a conveyor. Suits banquet halls, hospitals, schools and high-volume restaurants. Larger flight-type machines carry dishes on a belt without racks.
- Glasswashers and utensil washers: specialized machines for a bar's glassware or for heavy pots, pans and sheet pans.
Sizing by racks per hour
Count racks, not seats. Estimate how many plates, glasses, cups and pieces of cutlery a cover uses, divide by what fits in a rack, and multiply by the covers in your busiest hour. That is the demand the machine has to meet, with room to spare for the pots, pans and trays that also come back.
Manufacturers publish a rated racks-per-hour figure, but treat it as a maximum. It assumes the operator loads and unloads without a pause, which does not happen at peak. Undercounter machines clear the fewest racks, door-type machines considerably more, and conveyors the most; if your peak demand sits near the top of a machine's rating, move up a size.
Cycle time matters too. A short cycle keeps glasses moving at a bar, while a longer cycle may clean heavily soiled plates better. Many machines offer selectable cycles so one unit can do both.
High-temperature or low-temperature sanitizing
Every commercial dishwasher sanitizes as well as washes, and it does so one of two ways. A high-temperature machine uses a very hot final rinse, commonly around 82°C (180°F) at the rinse arms, to sanitize with heat. A low-temperature machine washes and rinses at lower temperatures and injects a chemical sanitizer, usually chlorine-based, into the final rinse.
Neither is better in every kitchen. The choice comes down to your electrical supply, your ventilation, what you wash and how you want to pay: more up front for a high-temperature machine, or an ongoing sanitizer cost for a low-temperature one.
- High-temperature strengths: dishes dry quickly because they leave the machine hot, no sanitizer is needed, and there is no chlorine to tarnish metal or leave an odour.
- High-temperature trade-offs: a booster heater and a larger electrical supply, more steam released when the door opens, and, depending on local codes, a condensate hood or ventilation over the machine.
- Low-temperature strengths: a lower purchase price, no booster heater, less steam and lower electrical demand.
- Low-temperature trade-offs: an ongoing sanitizer cost, slower drying, and chlorine can be hard on silver, aluminum and some plastics over time.
- Heat-recovery or ventless high-temperature models capture steam and use it to preheat incoming water, which can remove the need for a separate hood in some jurisdictions. Confirm with your local authority before counting on it.
Booster heaters, hot water and power
A booster heater raises the building's hot water to final rinse temperature. Many high-temperature machines have one built in; others need a separate booster mounted beside or under the machine. The building's own water heater still has to deliver enough hot water, hot enough, for the wash tank and the rest of the kitchen, so size it with your plumber.
Boosters draw a lot of power. Door-type and conveyor machines with built-in boosters commonly need 208 or 240 volt service and sometimes three-phase power, so confirm the voltage, phase and amperage on the spec sheet against your electrical panel before ordering. A machine built for the wrong supply cannot simply be plugged into a different outlet.
Water, drains and chemicals
Hard water leaves scale on heating elements, wash arms and rinse jets, which lowers rinse temperature, spots glassware and shortens the machine's life. Many manufacturers recommend water treatment or a scale-inhibiting filter where water is hard, so read the manual and the warranty terms on scale before you install without one.
Commercial dishwashers drain by gravity or with a built-in drain pump, and plumbing codes often require an indirect connection to the building drain, through an air gap or air break. Where the drain has to rise to reach the floor drain, a model with a drain pump can save re-plumbing. Grease interceptor rules are set locally, so ask your plumber or municipality.
Detergent and rinse aid, plus sanitizer on a low-temperature machine, are fed by small pumps from containers beside the machine. Many kitchens get the dispensing equipment through their chemical supplier, so decide who is supplying chemicals before the machine arrives.
Dish tables and flow
Set the direction of flow first. A door-type machine is fed from one side and emptied from the other, so decide whether dirty dishes travel left to right or right to left, and whether the tables run in a straight line or turn a corner. Many door-type machines can be installed straight-through or in a corner, but dish tables are built for one configuration.
The soiled table needs a scrap area, a pre-rinse sink or spray, and landing space for full racks. The clean table needs room for racks to drain and air-dry before they are stacked. A clean table that is too short forces staff to unload wet racks, which slows the line and leaves water spots.
- A soiled dish table with a pre-rinse sink and pre-rinse faucet.
- A clean dish table long enough for racks to drain before they are unloaded.
- Dish racks for plates, cups, glasses and cutlery, plus rack dollies.
- Overshelves or wall shelving above the tables for rack storage.
Daily care and common mistakes
A dishwasher runs every day, so daily care decides how long it lasts. Drain and clean the tank at the end of each day, pull and rinse the scrap screens and wash arms, check the rinse jets for scale, and delime on the schedule the manufacturer sets. Watch the temperature gauges, or test the sanitizer with test strips on a low-temperature machine, and log both if your health unit expects records.
- Buying on seat count and finding the machine cannot keep up at peak.
- Ordering a high-temperature machine without a booster, or without the electrical supply the booster needs.
- Skipping water treatment in a hard-water area.
- Forgetting the ventilation a high-temperature machine may need under local rules.
- Leaving no room on the clean side for racks to drain.
Common questions
What is the difference between a high-temp and a low-temp dishwasher?
- A high-temperature dishwasher sanitizes with a very hot final rinse, usually heated by a booster heater. A low-temperature dishwasher runs cooler and sanitizes with a chemical, usually chlorine-based, added to the final rinse.
Do I need a hood over a commercial dishwasher?
- Many jurisdictions require a condensate hood or ventilation over high-temperature door-type and conveyor machines because of the steam they release. Low-temperature and ventless heat-recovery models often avoid it, but check with your local building and health authorities.
Is an undercounter dishwasher enough for a restaurant?
- For a small café, bar or restaurant with a short menu, often yes. A full-service restaurant with a real dinner rush usually needs a door-type machine, because an undercounter unit cannot turn racks over fast enough at peak.
Can a dishwasher replace a three-compartment sink?
- Usually not entirely. Many Canadian health units still expect a way to wash, rinse and sanitize items that do not fit the machine, and large pots and pans rarely fit a rack. Check with your local health unit.
Can I return a dishwasher if it does not suit my kitchen?
- Special-order and freight equipment is not returnable once it has been delivered in good condition, so confirm the voltage, water supply, drain and fit before ordering.