Remove the slipcover from the sofa. As you remove each cover, pay close attention to its orientation on the cushion so that you can easily replicate it when you replace the cover.
Shake the slipcover vigorously to dislodge any dirt or debris.
Zip the slipcover closed. This will help preserve the interior seam and keep it from fraying.
Place the slipcovers in the washing machine by themselves. Do not overload the washing machine. Use the recommended amount of detergent for a medium load of clothing.
Wash with cold water to preserve the slipcover's cover.
Set the spin cycle to slow if your washing machine offers that option.
Preserve your slipcover's color (or follow the label's instructions) by hand-washing the slipcover in a bathtub filled with cold water and the same amount of detergent (or hand-washing detergent). Hang the slipcover until it does not readily drip before placing it in the dryer.
Place your slipcover in the dryer. Set the machine on low heat and tumble dry. Check on the slipcover toward the end of the cycle. Remove it when it is still slightly damp. Alternatively, to preserve your slipcover's color (or to follow the label's instructions), hang the slipcover out to air dry until it is only slightly damp.
Replace the slipcover onto the cushion. Allow it to air dry (flip it once or twice) before placing any throws or blankets on the sofa.