Where is the best location to draw a sample in reservoir sampling?

Drawing a sample from the midpoint of the reservoir, near the return line, is considered the best location for several reasons. This position allows for a more representative sample of the lubricant's quality and characteristics because it is typically where the fluid is circulating and mixing. The return line is where the lubricant re-enters the reservoir after passing through the system, allowing it to collect any contaminants and ensure you're getting a sample that reflects the actual condition of the fluid after it has been in use.

In contrast, drawing from the drain plug might yield sediment or sludge that has settled at the bottom, which does not represent the overall quality of the lubricant. Sampling from the side could also result in a less representative sample because it may be taken from a stagnant area that doesn't mix well with the rest of the reservoir. Similarly, taking a sample from the top may miss important contaminants that have settled. This highlights the importance of choosing a sample location that accurately represents the entire lubricant system's condition to ensure effective monitoring and maintenance.