What critical factor does NOT contribute to preventing back-siphoning?

In the context of preventing back-siphoning, the volume of the spray tank is not a critical factor. Back-siphoning occurs when there is a potential for contaminated water to be sucked back into a clean water supply due to a pressure differential, typically during filling operations. The primary factors influencing this phenomenon are related to the physical and operational characteristics of the filling system.

The length of the fill hose can play a role because a longer hose can create more resistance and potentially affect the likelihood of back-siphoning. The elevation of the hose end is critical as having the end of the hose below the water surface in the tank can increase the risk of back-siphoning. The pressure in the system is also vital since lower pressure can contribute to the potential for back-siphoning.

In contrast, the volume of the spray tank doesn't inherently impact the risk of back-siphoning; it is more about how the system is set up and operated rather than how much liquid the tank can hold. Therefore, understanding these dynamics helps operators to implement effective measures for preventing back-siphoning.