Straight answers to the questions operators ask about the three-compartment sink, from the correct wash-rinse-sanitize order and temperatures to sizing, setup and code. For choosing and specifying one, see our commercial sink guide.
A three-compartment sink is a commercial sink with three separate bowls used for manual warewashing in the order wash, rinse, sanitize. It is the code-required backbone of manual dishwashing in most commercial kitchens, letting you clean items that will not fit a machine and serving as backup when a dish machine is down. Most have integral drainboards on one or both ends for scraping and air-drying.
Scrape and pre-rinse dishes first, then work through three steps: wash in the first bowl with hot soapy water, rinse in the second with clean water, and sanitize in the third with hot water or a chemical solution. Air-dry on a drainboard; never towel-dry. Change the water when it gets greasy or cool. This wash-rinse-sanitize sequence is a core FDA Food Code requirement for manual warewashing.
The order is wash, rinse, sanitize, from the first bowl to the third, always preceded by scraping and pre-rinsing. Wash removes soil with hot detergent water, rinse clears the detergent with clean water, and sanitize reduces pathogens with heat or chemical solution. Then items air-dry on a drainboard. Running the steps out of order, or skipping the rinse, undermines both the detergent and the sanitizer and can fail an inspection.
The wash compartment should be at least 110°F (43°C) so detergent works and grease lifts, and many operators run it warmer. For the sanitize step, hot-water immersion sanitizing requires water at least 171°F (77°C). If you sanitize chemically instead, follow the product's temperature range, often around 75 to 100°F for chlorine. Use a thermometer to verify, and see our hot water requirements guide for supply planning.
For hot-water sanitizing, immerse items for at least 30 seconds in water at 171°F (77°C) or hotter. For chemical sanitizing, temperature depends on the sanitizer: chlorine works best around 75°F and loses effectiveness if too cold or too hot, while quats follow the manufacturer's range. Too-cold water weakens chemical sanitizers. Always pair the temperature check with a test-strip check of concentration, and confirm specifics locally.
For unscented chlorine bleach, a common target is 50 to 100 ppm, roughly a tablespoon of bleach per gallon of water, verified with chlorine test strips, not by eye. Quaternary ammonium sanitizers typically run 200 to 400 ppm per the label, and iodine around 12.5 to 25 ppm. Always mix to the product directions and test the concentration each time you fill, since strength drops as the solution is used.
Typical Food Code concentrations are chlorine 50 to 100 ppm, quaternary ammonium (quat) around 200 ppm and up per the label, and iodine 12.5 to 25 ppm, each with a minimum contact time. Chlorine acts fastest, needing only about 7 seconds of contact at 50 ppm. Concentration must be checked with the matching test strips at every fill and topped up as it depletes. Confirm the exact required range with your jurisdiction.
In most commercial kitchens, yes. A three-compartment sink is the standard code requirement for manual warewashing, and many jurisdictions require one even if you also have a dish machine. It does not replace a separate handwashing sink or a food-prep sink; those serve different purposes and cannot be combined with it. Requirements vary by locale and operation type, so confirm your specific needs with the requirements for your area.
Generally yes for manual warewashing under the FDA Food Code as adopted by most states, though the exact wording and exceptions vary. It is separate from, and does not replace, your handwashing sink or food-prep sink. Some very limited operations or those relying entirely on an approved dish machine may see different rules. Because adoption differs by jurisdiction, confirm the requirements for your area before you build.
Most jurisdictions require food trucks to have a three-compartment sink for warewashing plus a separate handwashing sink, along with adequate fresh and waste water tanks. Some allow reduced warewashing on very limited-menu units, but this is the exception. Space and water-tank sizing make this one of the tighter design challenges on a truck. Rules vary by city and county, so confirm the exact mobile requirements for your area.
Most health codes require bars to have a three-compartment sink (often a compact underbar version) for washing glassware, plus a separate handwashing sink. A glasswasher may supplement it but usually does not eliminate the requirement. The three bays still run wash, rinse, sanitize with a sanitizer solution in the third bay. Because underbar rules vary, confirm what your jurisdiction requires for a bar with your local health department.
Usually yes. Even a coffee or espresso shop that handles cups, pitchers, blender jars and utensils typically needs a three-compartment sink for warewashing plus a separate handwashing sink, and often a prep sink depending on the menu. Some very limited beverage-only operations may qualify for reduced requirements. Because it hinges on your exact menu, check the required-equipment guide and confirm with your health department.
Sizes vary widely. Compact bar units may have bowls around 10 inches, while standard kitchen models have bowls of 16 to 24 inches or more, with overall lengths from about 4 feet up past 8 feet once drainboards are included. The bowls must be large enough to fully submerge your biggest regularly-washed item, such as sheet pans or stockpots. Match the bowl size to your equipment; the sink guide covers sizing.
Choose bowl dimensions that let you fully immerse your largest routinely-washed item, since sanitizing requires complete submersion. If you wash full sheet pans or large stockpots, you need deep, wide bowls; a small-plate cafe can use smaller ones. Also plan drainboard space on both ends for scraping and air-drying. Undersizing forces awkward tilting and poor sanitizing. Our commercial sink guide walks through matching bowl size to your equipment.
It depends entirely on bowl dimensions. A common mid-size bowl (about 20 by 20 by 12 inches) holds roughly 20 to 25 gallons per compartment when full, so all three together can hold 60 to 75 gallons. Compact bar bowls hold far less, large pot sinks far more. This total feeds water heater sizing and drainage planning. Calculate from your actual bowl dimensions rather than a generic figure.
Fill the first bowl with hot detergent water (at least 110°F), the second with clean rinse water, and the third with sanitizer at the correct concentration and temperature. Set out test strips and a thermometer, and stage a scrape/pre-rinse area and a drainboard for air-drying. Verify wash temperature and sanitizer concentration before you start. Label the bowls wash, rinse, sanitize so the sequence stays consistent across staff and shifts.
Scrape and pre-rinse, then immerse and scrub in the wash bowl with hot detergent water. Move to the rinse bowl to remove all detergent. Then fully submerge in the sanitize bowl for the required contact time, at least 30 seconds for hot-water sanitizing or the label time for chemical. Finally, air-dry on a drainboard; do not towel-dry. Change water and re-test sanitizer as they get dirty or weak.
Change wash water whenever it turns greasy, cools below 110°F, or the suds are gone, and refresh rinse water when it gets cloudy with detergent. Re-test and replenish the sanitizer bowl regularly, since concentration drops as you use it and as soil accumulates. There is no single fixed interval; it is driven by soil load. Test strips and a thermometer, used often, tell you when it is time.
Yes. Each compartment's drain must discharge through an air gap, typically to a floor sink or drain with the required vertical separation, so wastewater can never back-siphon into the sink or potable supply. A direct drain connection is not allowed. The exact air-gap dimension and drain arrangement come from your local plumbing code, so confirm the specifics with your plumbing inspector during plan review.
Often yes. Because pot and pan washing sends a lot of fats, oils and grease down the drain, many jurisdictions require the three-compartment sink (and any pre-rinse) to discharge through a grease interceptor. The trap must be sized to the sink's flow. Requirements and sizing methods vary widely by locale. Confirm with your plumbing authority whether your warewashing sink must route through a grease trap and how large it must be.
Sizing is usually based on the total drainage volume of the sink bowls and the fixture's flow rate, using your local plumbing code's method (often a formula tied to bowl gallons and a drain-down time). A common approach sizes an under-sink interceptor to the combined bowl capacity; larger operations use exterior interceptors. Because methods and required sizes differ significantly by jurisdiction, have a plumber calculate it to your local code.
Wash in bowl one with hot detergent water to remove soil, rinse in bowl two with clean water to remove detergent, then sanitize in bowl three by fully immersing for the required contact time in hot water (171°F, 30 seconds) or a chemical solution at the correct concentration. Air-dry on a drainboard. Test the sanitizer with strips and check temperatures. Scrape and pre-rinse first so the wash water lasts.
The third compartment is the sanitizing step. After washing and rinsing, items are fully immersed there in either hot water at 171°F for at least 30 seconds, or a chemical sanitizer solution at the correct concentration and contact time. Sanitizing reduces pathogens to safe levels on already-clean surfaces; it does not clean, which is why wash and rinse must come first. Items then air-dry rather than being towel-dried.
No. Handwashing must be done at a dedicated handwashing sink, not in the warewashing sink or a food-prep sink. Using the three-compartment sink for handwashing risks contaminating dishes and the sanitizing solution and is a code violation in most jurisdictions. A separate, accessible handwashing sink stocked with soap and paper towels is required. Confirm your local handwashing-sink requirements as part of plan review.
Best practice, and code in many places, is to wash produce in a dedicated food-prep sink, not the warewashing sink, to avoid cross-contamination from dish soil and chemical sanitizer residue. If no prep sink exists, some jurisdictions allow produce washing in a cleaned-and-sanitized warewashing sink at designated times, but rules vary. Confirm locally, and consider adding a prep sink if you handle much fresh produce.
Yes, unscented chlorine bleach is a standard, inexpensive sanitizer for the third bowl. Mix to roughly 50 to 100 ppm (about a tablespoon per gallon) and verify with chlorine test strips, never by smell or eye. Use water around 75°F for best action, and immerse items for the required contact time. Do not mix bleach with other cleaners, and re-test as the solution depletes during use.
Label the bowls in order, wash, rinse, sanitize, so every staff member and shift runs the steps correctly. Many operators add a posted procedure showing the wash temperature, sanitizer type and concentration, and contact time, plus a reminder to air-dry. Some health departments look for this signage. Durable, waterproof labels or an adjacent laminated chart keep the process consistent and make training and inspections easier.
Compact bar or small stainless units can start around $400 to $800, standard kitchen models commonly run $800 to $2,500, and large pot sinks with long drainboards go higher. Faucets, pre-rinse sprayers and installation add to the total, and plumbing (air gap, possible grease trap) can be a bigger cost than the sink itself. Prices vary by size, gauge of steel and brand. Our sink guide covers what drives cost.
Each bowl needs hot and cold supply to the faucet and a drain that discharges through an air gap to a floor sink or drain, often routed through a grease interceptor for warewashing. A shared faucet or pre-rinse unit typically serves all three bowls. Backflow protection and correct trap and vent sizing apply. Because plumbing code details vary, have a licensed plumber design and install it to your local requirements.
A two-compartment sink has two bowls and is used in some settings for specific tasks, such as a prep sink or a limited warewashing setup where allowed. It does not satisfy the standard three-step wash-rinse-sanitize warewashing requirement on its own in most jurisdictions. Whether a two-compartment sink is acceptable for any given purpose depends entirely on local code, so confirm before relying on one for dishwashing.
Bowls are commonly 12 to 14 inches deep, but depth should be chosen so your largest routinely-washed item can be fully submerged, which is required for proper sanitizing. Deep stockpots and sheet pans call for deeper bowls. Too-shallow bowls force tilting and leave surfaces unsanitized. Balance depth with a comfortable working height for staff. Match bowl depth and width together to the biggest thing you wash regularly.
Start by clearing the strainer baskets and checking for grease buildup, the most common cause. A plunger or a hand auger through the drain often clears a soft blockage. Avoid harsh chemical drain cleaners in commercial lines, and never send grease down the drain, since a clogged or overloaded grease trap is a frequent culprit. If it recurs, have the interceptor pumped and the line professionally cleared.
In most jurisdictions, yes. The three-compartment sink is required as a manual warewashing method and backup even when a dish machine is present, and it handles pots, pans and oversized items the machine cannot. Some limited situations may differ. Because this is a common plan-review question with locally-specific answers, confirm the requirements for your area before finalizing the layout with a machine.
A scullery or pot sink is a heavy-duty compartment sink, often oversized and deep, dedicated to washing large pots, pans and cooking equipment that will not fit a dish machine. In many kitchens the three-compartment sink serves this role. The bowls are sized for stockpots and sheet pans and paired with long drainboards. It runs the same wash-rinse-sanitize process as any manual warewashing sink.