Why Are SCUBA Tanks Placed in Water for Refilling?

Each scuba tank is rated for a specific pressure (e.g., 3000 psi) and maximum pressure capacity. Air compressors to refill scuba tanks can include a water bath to cool tanks.

  1. Significance

    • Air tanks are placed in a holding container filled with water (water bath) during the filling process. The water bath provides a cooling environment to stabilize the warmed tank and a medium to detect any minor leaks in the tank walls while cleaning away surface salt and residue.

    Concern

    • Water baths sometimes are used in air refill stations to provide fast, hot fills for customers (divers) who are anxious to get back in the water. A major concern with water baths is the possibility of getting water into the tank, compressor or equipment, which could cause corrosion or contamination.

    Good Practice

    • According to Sandiegodiving.com in the article, "The Art of a Good Air Fill, " tanks should be filled to (or near) maximum working pressure. The maximum recommended fill rate for tanks is 300 psi per minute.

    Misconceptions

    • According to Fred Calboun, PE, in the article, "Scuba Tanks," a water bath during filling provides very little measurable cooling to stabilize the air tank (which is filled with warm air).

    Considerations

    • Allow adequate time to fill the tank in stages to provide optimum air fills. Fast fills can yield short fills; cooled water baths can promote overfilling tanks beyond their capacity.