Choosing a commercial dishwasher comes down to one question kitchen operators tend to underestimate: How many dishes need to move through the machine per hour? An undercounter dishwasher and a hood-type pass-through dishwasher both sanitize the same way, but they’re built for very different volumes. That difference continues with the plumbing, ventilation, and installation requirements, so it’s important what you’re getting into before ordering. This guide covers the difference between the two, the certification requirements in Canada, any electrical or plumbing needs, and how to find the best option for your kitchen.

The Core Difference Between Undercounter and Hood-Type Dishwashers

An undercounter dishwasher is a compact, single-tank unit that sits, as the name suggests, under a counter or prep station. Racks load through a front-opening door, and the machine runs a full wash-and-rinse cycle in approx. 2 to 4 minutes, topping out around 20 to 30 racks per hour. It's the machine most commonly found behind a bar, in a coffee shop, or in any kitchen where dish volume is steady but not high.

A hood-type pass-through dishwasher, sometimes called a door-type dishwasher, is a larger single-tank unit built to run continuously through a busy service. Racks slide in one side, a hood lowers over the top, and the cycle runs in as little as 60 to 90 seconds, with output around 60 to 65 racks per hour, more than double an undercounter machine. That higher output draws more water, more power, and in most cases, more local code requirements.

Both machines are available in high-temperature and low-temperature configurations. High-temp machines sanitize with a 180°F final rinse and need a booster heater to reach that temperature. Low-temp machines sanitize chemically, usually with a chlorine-based rinse additive, and run on standard hot water without a booster. We carry both configurations styles, including the Moyer Diebel NEXUS N900 and Stero SUH-1/SUL-1 for undercounter options, and the Hobart Centerline CDH-1/CDL-1 and DIHR HT 11 USA for our hood type options.

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Certifications: What to Confirm Before You Buy

Whichever type you choose, two certifications are required for commercial kitchens. They need to be certified for both sanitation and electrical safety. You can read our article breaking down the certifications here.

The sanitation certification is to ensure that the dishwasher is reaching the proper temperature to correctly sanitize the dishes inside, and also ensuring that the dishwasher components themselves can withstand the water and high temperatures over time.

The electrical certification is to ensure that the machine is safe to operate. This is especially important for dishwashers since they run with plumbing at very high temperatures. Both water and high heat can destroy components or cause potential fires, so this shouldn’t be overlooked.

Plumbing Requirements for Each Type

A high-temp machine, undercounter or hood-type, needs incoming water heated to at least 140°F with a booster heater. This is often built in, raising the final rinse to 180°F for sanitizing. A low-temp machine skips the booster and relies on a chemical sanitizer dispensed during the rinse cycle instead, which simplifies the plumbing but adds an ongoing chemical cost. It’s important to keep in mind that low temp dishwashers, since they use a chemical to sanitize, can often leave a chemical coasting on the dishes themselves, which customers could potentially taste when using glasses or cutlery. If you want to provide a high-quality experience to customers, this should be heavily considered.

Drain requirements apply across both types under most Canadian plumbing codes: a dishwasher cannot connect directly to a drain line. It needs to discharge through an air gap into a floor drain to prevent wastewater from siphoning back into the machine. A hood-type unit typically needs a larger drain line and, depending on your municipality's bylaw, may need to pass through a grease trap before hitting the drain. An undercounter machine's lower volume usually clears that on a standard floor drain connection. Your local code always has the final say though, so it’s important to get confirmation before planning out your project.

Ventilation Requirements: The Real Cost

This is the requirement that surprises the most operators. A low-temp undercounter dishwasher generates minimal steam and, in most Canadian cities, doesn’t require a hood at all. A high-temp undercounter unit produces more steam at the 180°F rinse but, given its lower cycle frequency, is often still exempt. Again, this is worth confirming with your local health inspector before finalizing a layout.

A hood-type pass-through dishwasher is a different story. Running a 180°F sanitizing rinse continuously through a busy service releases a steady volume of steam and heat, and most Canadian regions require a Type II condensate hood over the machine to manage it. This is a ventilation-only hood, not a grease hood, but it still needs to be sized, ducted, and installed to code, which can add thousands of dollars to the project. Heat-recovery models, like the DIHR Optima 12 HR Plus, capture and reuse that steam energy internally, which can reduce the ventilation load and, in some layouts, change what your inspector requires.

Which Dishwasher Should I Buy Based on Volume?

Dish volume, not kitchen size, should decide this. An undercounter dishwasher covers most operations doing up to roughly 150 covers a service, along with any bar, cafe, or glass washing station where the dishwasher supplements rather than carries the full load. Once a kitchen consistently runs 150 to 400+ covers a service, the undercounter dishwasher is too slow to keep up with demand. This will just cause bottlenecks in the kitchen, and leave piles of dishes lingering as you’re waiting for cycles to finish. That's the volume where a hood-type unit starts paying for itself. Kitchens running well beyond that, institutional cafeterias and high-volume buffets, typically move to a conveyor system, a different category of machine altogether.

Why This Installation Must be Done by a Qualified Technician

Regardless of which machine you choose, installation is not a DIY job. All dishwashers require a licensed plumber to handle the water supply and the drain connection correctly to ensure there are no backflow problems. Booster heaters and hood-type machines in particular often call for a 208-240V circuit, and larger units run on three-phase power, which needs a licensed electrician. Incorrect installation is the largest causes of warranty issues for dishwashers, and it’s the reason most brands offer the added service to customers. It’s important to keep in mind that a dishwasher that was incorrectly installed usually voids the manufacturer’s warranty, so you shouldn’t play games here. If you're not sure who to call locally, our team can point you toward a qualified installer to make the process easier.

Frequently Asked Questions

Is one type noticeably louder than the other?

Yes. An undercounter machine runs a slower, quieter cycle that works fine tucked behind a bar or in an open-concept kitchen within earshot of guests. A hood-type machine runs faster, cycles more water, and is audibly louder in operation, which is why it's almost always placed in a back dish pit rather than anywhere near the dining room.

If my dishwasher goes down mid-service, how much does that hurt me?

It depends heavily on which type you're running. Because a hood-type machine typically carries most of a busy kitchen's dish load, a breakdown mid-service backs up racks fast. Most operators either fall back on a three-compartment sink temporarily or keep an emergency tech on-call to minimize the downtime. An undercounter machine going down is lower stakes in a slower kitchen, since staff can often hand-wash to keep pace, but it still hurts behind a busy bar during a rush.

How much daily volume before I outgrow an undercounter dishwasher?

There's no single number, but once your kitchen consistently runs past roughly 150 covers a service, the 20 to 30 racks an hour an undercounter machine handles typically can't keep pace, and a hood-type unit becomes the better fit.

Can I add ventilation later if my kitchen's volume grows into a hood-type dishwasher?

It's possible, but far easier and cheaper to plan the ductwork and electrical capacity during your original build-out than to retrofit a hood into a finished kitchen. If growth looks likely within a few years, discuss hood placement with your contractor even if you start with an undercounter machine.

Is a heat-recovery hood-type dishwasher worth the extra cost over a standard model?

For a kitchen running high volume most days of the week, the water and energy savings from a heat-recovery model like the DIHR Optima 12 HR Plus typically offset the higher upfront cost within a few years, and may also reduce the ventilation load your kitchen needs to accommodate. For lower or seasonal volume, a standard high-temp or low-temp unit is usually the more practical choice.

Finding the Right Dishwasher for Your Kitchen

The undercounter versus hood-type debate is all based on volume. Match the machine to how many racks you need to move through your dishwasher in an hour, confirm the certifications on whatever you choose, and plan the plumbing and ventilation with your contractor before the equipment arrives rather than after. At Phoenix Food Equipment, we carry both undercounter and hood-type pass-through dishwashers in high-temp and low-temp configurations, and our team is glad to walk through your service volume, kitchen layout, and local code requirements to help you land on the right machine, including financing options.

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