What should be done to prevent backflow in water systems?

To prevent backflow in water systems, all of the listed options contribute effectively to maintaining water quality and protecting the system from contamination.

Installing a spring valve can help manage the direction of flow in a system and prevent backflow by utilizing the mechanical properties of the valve to ensure that fluid only flows in one direction. This type of valve uses spring tension to close when there is a reverse flow, thereby providing a physical barrier to backflow.

Ensuring proper pressure management is vital in preventing backflow as it helps maintain a constant flow rate and prevents reverse flow conditions that can allow contaminants to enter the clean water supply. When the pressure in the distribution system is higher than in the potentially contaminated area, backflow is less likely to occur.

Using a check valve is one of the most common and effective methods for backflow prevention. Check valves automatically close when fluid attempts to flow in the reverse direction, thus providing a fail-safe mechanism against contamination from backflow. These valves are widely utilized in plumbing and water distribution systems specifically for this purpose.

Since each of these options plays a critical role in preventing backflow, selecting "All of the above" accurately reflects the comprehensive approach needed to maintain water system integrity and safety.