A Backflow test gauge (differential pressure gauge) should be stored with all needles:

For the storage of a backflow test gauge, it is essential to ensure that it is kept in the right condition to maintain its functionality and accuracy. Storing the gauge with all needles opened and hosed drained helps to prevent any residual water or debris from causing corrosion or damage to the internal mechanisms of the gauge. By leaving the needles open, any moisture is allowed to evaporate, reducing the risk of rust and ensuring that the gauge remains in optimal working condition for future testing.

Additionally, maintaining a dry storage environment is crucial for any precision instrument, as it mitigates the risk of water damage and ensures that the sensitive components within the gauge do not become clogged or malfunction due to trapped moisture. This practice is essential for prolonging the life of the equipment and ensuring reliable performance during backflow testing.

Keeping the gauge secured in a toolbox or in a protective case, while helpful for physical protection, does not address the need to prevent moisture accumulation and the integrity of the internal mechanisms, which is why that option is not as effective for ensuring long-term care of the gauge.