What is my dishwasher’s prewash option for, and does it need detergent?

Treat the name as a clue, not a complete instruction: manufacturers may use “prewash,” “presoak,” or another label differently. Find the matching option in your dishwasher’s manual and look for its stated purpose, which cycles allow it, and whether you must select it before starting. As one model-specific example, an older GE manual describes Power Presoak as an option for heavily soiled or dried-on or baked-on food, selected before starting. That example does not establish what your dishwasher’s setting does. [S1]

If you don’t have the manual, note the exact model number from the appliance label and use it to locate the matching manual or ask the manufacturer. Avoid deciding based only on a similar-looking control panel.

Not without checking your model’s directions. Look for a manual section called “detergent,” “dispenser,” or “using detergent,” then check whether it specifies a prewash compartment, an open cup, or only the main detergent cup for your chosen cycle. Also check whether the manual gives separate instructions for that option and cycle.

The cited older GE manual says its wash cycles other than Rinse Only use detergent in the main cup, and cycles with two washes also use the open cup. Those instructions apply only to the models covered by that manual; they are not a general rule for other dishwashers. [S1] If the manual doesn’t explain the option or dispenser clearly, ask the manufacturer using your model number rather than guessing.

Record the brand and full model number from the appliance label, plus the exact wording on the control. Don’t rely on a family name or a manual for a similar model: features and dispenser instructions can differ. Compare the model listed on the manual with your label, then look specifically for the prewash option, compatible cycles, when to select it, and detergent-cup directions.

A useful note to prepare is: “Brand: [brand]. Model: [full model number]. Control label: [exact wording]. Cycle I plan to use: [cycle]. Manual section I checked: [section or page].” If you’re contacting support, ask: “For this model and cycle, what does [option name] do, and which detergent cup or cups should I use?”

Use this short check before starting:

1. Identify the exact dishwasher model and selected cycle.
2. Read the manual’s description of the prewash or presoak option; confirm whether it applies to that cycle and whether it must be selected before starting.
3. Follow the manual’s detergent directions for that specific cycle and option. Don’t add detergent to an extra cup unless the instructions say to.
4. If the manual is missing or unclear, confirm the instructions with the manufacturer rather than inferring from another model.

For example, suppose you have a heavily soiled load and your manual says its presoak option is intended for that kind of soil. Check whether your chosen cycle supports it, then follow that same manual’s dispenser directions. The GE example supports only the instructions for the models it covers; it does not establish what any other dishwasher’s setting or detergent cups require. [S1]