What is a recommended precaution for using water baths?

Adding a phenolic detergent to the water bath is recommended as it serves an important role in preventing contamination. Water baths are often used for a variety of laboratory procedures where samples can be sensitive to microbiological contamination. By incorporating a phenolic detergent, you effectively reduce the risk of bacterial growth, ensuring that the samples remain uncontaminated during experiments.

Using sodium azide, while it may inhibit bacterial growth, is not advisable in water baths because it can be toxic and hazardous, creating safety concerns for laboratory personnel. Additionally, leaving the water bath plugged in while filling or emptying poses a significant electrical and burn hazard. Thus, adding a phenolic detergent is the safest and most effective practice for maintaining cleanliness and preventing contamination in water baths.