can you use this to clean the washing machine drain pipe?

The Drain Care Buildup Remover help prevent clogs and remove years of buildup restoring the flow to slow running and partial clogged drains. For Drain Care® to work properly, you need to establish a partial flow so the enzymes can reach further down the pipes and start the cleaning process. To treat laundry lines: Pour 1 ounce of Drain Care into laundry line then flush with 16 ounces of warm water. Do not use for 6 hours. Repeat this process for 3 consecutive days. Use the Drain Care once a month in sinks, toilets, garbage disposal and grease traps to keep lines flowing freely. Thank you for your inquiry. We appreciate your business. Best Regards, Zep Retail Technical Support

Is this really for a 64 oz bottle? Home Depot & Lowes both sell that size for $10.00.

Current info is that Amazon is less expensive (Home Depot $12.87) and (Lowes $12.98) 02/19/2023.

Can this be used for sink overflow drains? if not, which zep product is best for this use?

Yes. Pour 1 ounce of the Zep Liquid Drain Care Build-up Remover into the overflow drain, followed by 16 ounces of warm water. Do not use the sink for 6 hours. Repeat applications for 3 days consecutive days. Use once a month to prevent reoccurring build-up. Thank you for your inquiry. We appreciate your business and opportunity to service you. Zep Inc. Retail Technical Support Team