My washer will drain into a utility tub/sink. I need to know if I will need a 18 or 19 gallon capacity sink to accommodate the discharged water.

Using the conversion factor that 1 cubic foot is approximately equal to 7.48 gallons, to hold 18 gallons of water, you would need a utility tub/sink with a capacity of about 2.22 cubic feet (18 gallons ÷ 7.48 gallons/cubic foot). A 5.5 cubic feet capacity laundry tub should be more than sufficient for a washer with a capacity of 5.5 cubic feet, like the Energy Star® Certified LG Impeller Smart Compatible Extra Large Top-Load Washer ( Alpine White ), Model # WT8400CW...^Ivan.