During the expansion and drainage test, how often should you record the level of accumulated solution in the cylinder?

Recording the level of accumulated solution in the cylinder every 30 seconds during the expansion and drainage test provides a balance between gaining enough data points to observe trends and changes in the accumulation level without overwhelming the testing process. This interval allows for a consistent monitoring of the solution's behavior over time, capturing the dynamics of the expansion and drainage effectively.

Choosing a timeframe that is too short, such as 15 seconds, could lead to unnecessary interruptions and might not yield significantly different data from each reading, while selecting a longer interval, such as 45 or 60 seconds, could result in missing critical changes in the solution level. Therefore, 30 seconds is a practical and effective choice that promotes accuracy while allowing sufficient observation.