According to NFPA 25, when should an antifreeze solution in a sprinkler system be tested for its concentration?

The requirement to test an antifreeze solution for its concentration annually is rooted in safety and system performance. Over time, the concentration of antifreeze in a system can change due to factors like evaporation, leakage, or dilution from water adding into the system. Regular annual testing ensures that the antifreeze solution maintains the correct concentration necessary to prevent freezing in pipes, particularly in systems that operate in environments prone to low temperatures.

Maintaining the proper concentration is crucial because if the concentration is too low, it might not effectively prevent freezing, leading to potential pipe bursts and water damage. Conversely, if the concentration is too high, it could lead to issues such as improper flow characteristics or increased viscosity, impacting the performance of the sprinkler system when required.

The other suggestions, such as testing every six months or biannually, while they may seem proactive, do not align with the NFPA 25 guidelines for antifreeze solutions. Additionally, only testing when a leak is suspected does not allow for consistently verifying the antifreeze solution's effectiveness, which poses a risk if the system's integrity is compromised.