Recirculating vs Fill-and-dump Dishwashers

When shopping for a commercial dishwasher, you'll likely come across the terms "recirculating" and "fill and dump," but what do they mean for your business? Commercial dishwashers use one of these two methods to clean, rinse, and sanitize the wares inside them, and from the outside, it can be hard to tell which is which. We'll go over the differences here so you can choose the dishwasher that best fits your needs.

• How Do Dishwashers Work?
• Recirculating Dishwashers
• Fill-and-dump Dishwashers
• Recycling Water
• Pros & Cons

How Does a Commercial Dishwasher Work?

Commercial dishwashers sanitize wares to an extreme degree, either by utilizing powerful chemical sanitizers or by soaking the dishes with very hot water.¹ One of these two methods is required for wares to come out sanitized enough to satisfy the health inspector, as well as to protect your guests from any potentially harmful microbes.

Chemical dishwashers are often called low-temp dishwashers, even though the water used in them can still be hot enough to burn you (around 140 degrees Fahrenheit). This is in comparison with high-temp dishwashers, which must achieve temperatures of at least 180 degrees Fahrenheit to fully sanitize the wares. High-temperature dishwashers typically utilize a booster heater to raise water from 140 degrees Fahrenheit, which is what most building water heaters can reach, to the 180 degrees Fahrenheit necessary for sanitization. The high heat kills any bacteria, fungus, or other microbe that could be lingering after a meal.

Likewise, the low-temperature dishwashers rinse the dishes with powerful chemicals that kill anything growing on your wares. For more information on how these pieces work, consult our low- vs high-temperature dishwashers guide.

What is a Recirculating Dishwasher?

If high- and low-temperature dishwashers refer to the way a dishwasher sanitizes its wares, what does a recirculating dishwasher do? "Recirculating" refers to the way the machine uses water to rinse debris from food. A recirculating dishwasher, which is almost always a high-temperature model, filters and reuses the hot water, which saves energy over having to reheat an entire load of water for every use. Since commercial dishwashers run fast cycles and are used frequently over the course of the day, recirculating water ends up saving you a significant amount in energy bills.

Ventless energy-recovery dishwashers use the heat of the outgoing water to heat up the new rinsing water, which is another way these dishwashers improve efficiency. Ventless energy-recovery is a feature of some high-end dishwashers, but if you can afford the initial investment, the energy savings can eventually offset the higher initial cost.²

A recirculating dishwasher uses approximately half the water a fill and dump does.

What is a Fill-and-dump Dishwasher?

The other major type of dishwasher does exactly what the name suggests; it fills up with water, washes the dishes, then dumps that water out. This requires less machinery and less complexity than a recirculating dishwasher, but is less utility efficient because you only get one use out of each load of water. Many chemical dishwashers are fill and dump because the chemicals need to be replenished with each load. On the other hand, fill-and-dump dishwashers don't need a booster heater to reach the high temperatures necessary for sanitization, so they use less electricity.

Are recirculating dishwashers always high temp?

It's hard to speak across the industry, but in general high-temperature dishwashers are also recirculating and low-temp dishwashers are fill and dump. You may find a few exceptions to this rule, but because low-temperature dishwashers use chemical sanitizers, they must use new water with a specific amount of chemicals for each load, and thus can't be recirculating units.

Do Commercial Dishwashers Recycle Water?

Yes, commercial dishwashers recycle water in whatever ways they can. Fill-and-dump dishwashers will reuse the rinse water from the cycle before as the wash water for the next cycle, while recirculating dishwashers reuse the same wash and rinse water for multiple cycles, with a filter cleaning out any leftover debris. Some high-temperature dishwashers are even eligible for ENERGY STAR® rebates in some areas because they're so water efficient. The amount of water each individual unit uses will vary, with some designed to be exceptionally efficient.

Pros & Cons of Recirculating & Fill-and-dump Dishwashers

References

1. Choosing a Fill-Dump vs a Recirculating Dishmachine Hobart. Accessed July 2021.
2. High- or Low-temperature Dishwashers Hobart. Accessed July 2021.