The water supplied to the water seal on a packed pump should be _____ in relation to the liquid being pumped.

The correct answer indicates that the water supplied to the water seal on a packed pump should be maintained at a pressure that is higher than that of the liquid being pumped, specifically in the range of 5-10 PSI greater.

This pressure differential is vital for preventing the backflow of the liquid into the pump's seal, which can lead to leaks and ultimately cause pump failure. By keeping the water supply at a higher pressure, it creates a barrier that helps to maintain the integrity of the seal, ensuring that the pump operates efficiently and effectively. This also aids in reducing the risk of contamination of the circulating water and the conveyed liquid, which is important for operational safety and compliance with environmental regulations.

The other choices reflect inadequate pressure differentials, which might not provide sufficient protection against backflow or seal failure. Each of those lower ranges would increase the likelihood of seal leakage, thereby compromising the pump's performance and longevity. Maintaining the appropriate pressure difference is essential for optimal pump operation and the longevity of its components.