A 15% decrease in full flow pressure during a quarterly main drain test on a standpipe is classified as what type of deficiency?

A 15% decrease in full flow pressure during a quarterly main drain test on a standpipe is classified as a critical deficiency due to the significant impact it can have on the system's ability to supply adequate water for fire protection. Fire protection systems are designed to operate effectively within specified pressure ranges to ensure that water is delivered to the fire suppression devices at the necessary flow rates.

When the pressure drops by such a substantial amount, it suggests possible issues such as a breach in the system, blockages, or failures in the water supply that could hinder the system's performance during an emergency. Critical deficiencies require immediate attention and rectification to ensure that the system remains functional and compliant with fire safety standards. Understanding and addressing this type of deficiency is vital for maintaining the efficacy of fire protection measures and ensuring safety in case of a fire incident.