Every page competing for this question teaches wash, rinse, sanitize and then hands you back to the bottle. The top-ranked guide in the category runs past two thousand words and answers the dosing question with a single instruction to check the product label. That is a referral to a sticker, not an answer.

You need three inputs: ounces of concentrate in the case, ounces the label calls for per gallon, and gallons your wash bay actually holds. Multiply the last two to get ounces per turn, then divide the case into it.

Worked on a 20 gallon bay at half an ounce per gallon, that is 10 fl oz per turn. A four by 3.78 L case holds roughly 511 fl oz, so it clears about 51 turns. A two by 2.5 L dispenser case holds roughly 169 fl oz and clears about 17. A single 2.5 L cartridge clears about 8.

Operators do not search for detergent cost. They search for a substitute for a named brand, because that is how the frustration presents itself. One r/restaurateur thread puts it plainly: the soap is very expensive, and the dispenser occasionally malfunctions and eats through product. Nobody in that thread could verify the cheaper alternative being suggested, because nobody publishes yield.

A second thread on r/restaurantowners states the gap almost verbatim. An owner costing out a dish machine cannot locate annual cost information for detergent and chemicals anywhere. The best answer he received was a per-gallon figure with the honest caveat that consumption per rack varies by machine. He was handed an input and no method.

The method is the divide above. Work out turns per case at your own bay volume for your current product and for the candidate. If the candidate needs twice the ounces per gallon, its lower case price evaporates. If it doses the same and costs less, you have a defensible switch instead of a rumour.

A sink turn is not just chemical. It is a person draining a bay, wiping the walls, refilling to working level, waiting for temperature, and re-dosing. Budget six to eight minutes for that sequence on a 20 gallon compartment. Nobody schedules it, everybody pays for it.

Change the water when it stops holding suds, when grease films the surface, or when it drops below your minimum wash temperature, whichever comes first. Most operations settle at two to four turns per shift. Put a clock rule on it rather than leaving the call to whoever is tired at the end of service.

Three turns a day at seven minutes is 21 minutes daily, close to ten hours a month of paid time spent moving water. That figure is what makes a dish machine look sensible at higher covers, and it is also why a small operator running 40 covers a service is usually right to keep the sink and skip the capital, the rinse aid and the service contract.