•  the geometry of the wash items (e.g. trays, glassware, change parts, containers);
•  the nature of the contamination (e.g. Greasy, Aqueous, Proteinous)

Typically stages include:

•  Pre-rinse; hot water spray or cold for proteinous contamination. The wash water is recirculated to reduce consumption.
•  Recirculated washes, with or without detergent(s), neutral, or alkaline to break down greasy contaminants followed by a neutralising weak acid wash.
• Multiple recirculated  post-rinses, hot or cold.
• Final WFI rinse to displace residual wash water, with a low conductivity target.
• Drying by sterile filtered hot air
• Cooling,  line purging.

Ultra-washers further add these enhanced process capabilities:

•  Pre-steaming to remove gross contamination
• Pre-rinse with superheated water spray
• Drying by vacuum
• System SIP

Attention to detailed design is needed to minimise the carry-over of fluids between stages which would reduce effectiveness and increase the risk of cross-contamination between loads. This demands excellent free-draining, which leads to a requirement for all surfaces to be highly polished, sloped to drain, an absence of deadlegs and widely radiused chamber corners.