Which of the following is a sign that a drain field may be failing?

Pooled water is a significant indicator that a drain field may be failing. When a drain field operates correctly, wastewater is absorbed into the soil and utilized by vegetation in the area. If there is an accumulation of water on the surface, it suggests that the soil has become saturated and is unable to absorb additional wastewater. This condition can result from a breakdown in the system, such as clogging in the absorption trenches or soil, or reduced permeability of the soil due to compaction or bio-mat formation.

Healthy grass growth, while it may suggest some degree of functionality in the drain field, can also occur if there is an overabundance of nutrients in the soil, which doesn't directly indicate a problem with absorption or overall system health. Dry soil typically suggests that the drain field is functioning well, as water is being absorbed as it should. Visible pipes, unless specifically problematic or damaged, do not inherently indicate a failure of the drain field system; they might simply be functional components of the system that are not causing an immediate issue. Therefore, pooling of water is the clearest and most direct sign of a failing drain field.