Which backflow prevention assembly is good for both back siphonage and back pressure?

The double check valve assembly is designed to protect against both back siphonage and back pressure. This assembly consists of two check valves arranged in series, which provides a critical barrier against the reverse flow of contaminated water into the potable water supply.

When it comes to back siphonage, if there's a drop in pressure in the potable water system, the double check valve assembly helps to prevent untreated water from being drawn back into the system due to the negative pressure. For back pressure, which occurs when the pressure on the non-potable side exceeds that of the potable side, the two check valves work together to create resistance and prevent any backflow.

On the other hand, other assemblies such as the spill-resistant vacuum breaker and the atmospheric vacuum breaker only safeguard against back siphonage and are no protection against back pressure. The reduced pressure principal assembly does provide protection against both back siphonage and back pressure but has a more complex mechanism involving a pressure differential that might not be necessary for all applications, whereas the double check valve assembly is often simpler and adequate for situations where moderate risk of contamination exists. This makes the double check valve assembly a commonly used choice in various irrigation and plumbing applications.