Drip systems are often described as recovery or non-recovery. The difference is what happens to the solution that runs off.
Non-recovery
Excess solution drains away to waste. This uses more nutrient and water, but it avoids building up salts or pathogens in the solution.
Recovery
Excess solution is collected and pumped back to the reservoir. This saves water and nutrient, but the solution must be monitored more closely, because its balance changes over time.
Choosing
Consider how much time you want to spend monitoring, and how much water and nutrient you want to use.