Walmart offers the Instant Power Septic Shock 2-Liter Bottle for $4.28. Opt for in-store pickup to cut it to $4.24 and avoid the $5.99 shipping charge. That's tied with our mention from a week ago as the lowest price we've seen. (It's the best deal now by $6.) It's designed to break down clogs and restore lateral/leach field lines.