Backflow Preventer vs. SS Check Valve: What’s the Difference?

The main difference between a backflow preventer and a check valve is their purpose and level of protection. 

Backflow preventers specifically protect potable water from contamination with multiple layers of protection.

Check valves prevent reverse flow in general applications with only a single barrier.

This post dives deep into the differences between these devices and how to choose the right one for your specific needs.

What is Backflow?

Backflow occurs when water flows in the reverse direction through a pipe or system. This unwanted reversal happens due to two main causes:

1. Back pressure occurs when downstream pressure exceeds supply pressure, forcing water backward. This can happen in heating systems, pumping stations, or elevated tanks.
2. Back siphonage happens when supply pressure drops significantly, creating a vacuum that pulls water backward. Common causes include water main breaks, fire hydrant use, or high water demand.

What is a Backflow Preventer?

A backflow preventer is a specialized plumbing device installed where potable water connects to potentially hazardous systems. Its sole purpose is preventing contaminated water from flowing back into clean water supplies.

These devices are typically installed at cross-connection points: where municipal water enters buildings, at connections to appliances like washing machines, or where irrigation systems connect to water supplies.

Backflow Valve Parts

Backflow preventers contain several key components:

• Check valves (typically two) that close when flow reverses
• Relief valve that opens to discharge water if backflow occurs
• Test ports for mandatory testing and certification
• Shutoff valves for maintenance and testing
• Strainers to protect internal components from debris

These parts work together to create a system that prevents contamination even if one component fails. This redundancy is what makes backflow preventers more reliable than simple check valves.

What is a Check Valve?

A check valve is a simple mechanical device that allows flow in one direction while preventing flow in the opposite direction. 

Check valves operate using a disc, ball, or flapper that moves with water flow. When water flows in the intended direction, the mechanism opens; when flow stops or reverses, it closes against a seat.

Stainless steel check valves are particularly popular for their corrosion resistance and durability.

Limitations of Check Valves

While effective for general applications, check valves have important limitations:

• No secondary protection if the valve fails or becomes blocked
• Vulnerable to water hammer damage if they close too quickly
• May leak if debris prevents proper seating
• Not designed specifically for protecting potable water

These limitations explain why check valves aren’t suitable substitutes for backflow preventers in applications where water safety is critical.

Backflow Preventer vs Check Valve: Key Differences

While both devices prevent reverse flow, their applications, protection levels, and features differ significantly:

The primary difference is that backflow preventers are specifically designed for health and safety protection, while check valves are general-purpose flow control devices.

Choosing the Right Valve to Prevent Backflow

When deciding between a backflow preventer and a check valve, consider these factors:

• Application purpose: Is this for protecting potable water or simply preventing reverse flow?
• Local codes: Many jurisdictions mandate specific backflow preventers for certain applications
• Level of hazard: Higher hazards require more sophisticated protection
• Maintenance requirements: Backflow preventers require regular testing and certification

For potable water protection, always choose a proper backflow preventer. For general industrial applications where reverse flow is merely inconvenient rather than hazardous, a quality stainless steel check valve may be sufficient.

Conclusion

The choice between a backflow preventer and a check valve depends on your specific application and safety requirements. 

For potable water protection, always choose a backflow preventer despite its higher cost to ensure proper health safeguards.

For industrial applications where contamination isn’t a concern, stainless steel check valves offer a more economical solution..

Consider consulting with a licensed plumber or engineer when installing either device, especially for applications connected to municipal water systems.