Do not use standard liquid or gel drain cleaners in exterior drains. The potential for groundwater poisoning, pipe damage, and personal injury far outweighs any minimal chance of success.
Exterior drains that collect surface water (yard drains, driveway trench drains) inevitably carry fine particles of dirt, sand, and gravel. Unlike organic matter, sediment does not dissolve. It settles in low spots and compacts into a hard, abrasive sludge. drain cleaner outside
However, using a standard drain cleaner outside is a fundamentally different proposition than using it indoors. This article provides a comprehensive examination of the types of outdoor clogs, the chemistry of drain cleaners, the specific risks of using them in an exterior environment, and the safer, more effective alternatives. Before selecting a tool, you must identify the enemy. Indoor clogs are typically composed of organic matter (hair, skin cells, food grease, soap scum). Outdoor clogs are a different beast entirely. Do not use standard liquid or gel drain