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Short answer: There is no defensible universal bag count. Ice requirements depend on actual water volume, starting temperature, ice temperature and form, heat gain, insulation, and the intended measured result.
Use measurement, not a fixed recipe
- Confirm the container's actual filled volume and a stable, safe entry and exit.
- Measure the starting water temperature with a suitable thermometer.
- Add ice in stages, stir without entering, and remeasure after the mixture stabilizes.
- Record the setup-specific result instead of assuming it transfers to another container, day, or environment.
A simplified formula can be misleading because melting ice absorbs heat differently from merely cooling water, and real setups gain heat from air, sun, the container, plumbing, and the user. IronThaw therefore does not publish a universal pounds-per-gallon shortcut as a guaranteed result.
Do not confuse setup math with health guidance
A measured water temperature is not a recommendation for exposure. No universal beginner temperature or duration is established. Follow equipment instructions, health guidance, supervision, symptoms, and safe-exit conditions.
Handling and safety
- Keep electrical equipment dry and follow all manufacturer installation and operating limits.
- Do not enter while large ice masses, unstable footing, blocked drains, or an unreliable exit create a hazard.
- Keep the head above water; never hyperventilate or hold the breath in or near water.
- Stop for uncontrolled breathing, confusion, weakness, loss of coordination, chest pain, faintness, or inability to exit safely.
Safety source
Source: National Weather Service cold-water safety.