backflow-preventer valve: "shall provide protection where a potential health hazard does not exist": can it be used in a house?

Question

Ideal for use where Lead-Free valves are required. Designed for installation on potable water lines to protect against both backsiphonage and backpressure of polluted water into the potable water supply. [This model] shall provide protection where a potential health hazard does not exist.

ASSE® Listed 1024

CSA® Certified

Meets the requirements of NSF/ANSI/CAN 61*

Does this language on the specification indicate that the valve may, or may not, be used indoors on the house side of the water meter? I'm confused by the fact that it can protect against polluted water being siphoned back into the potable water supply and yet it shall be used where there's no risk of health hazard.

EDIT: While I was trying to search the internet for an answer to my question I found this CDC document relating to legionella.

Answer 1

Levels of hazard

The US plumbing codes call out different backflow preventers for different applications based on the level of risk involved. Your dual check valve is intended for lower-hazard applications where the worst risk is water that say is a bit rusty, smelly, or discolored, such as an iron-piped fire sprinkler system.

As you increase the hazard from mere pollution to health-risking contamination, the codes require more robust preventers to be installed. For instance, the contamination risk posed by an irrigation system with a chemical feeder and pump in it would require a reduced pressure zone backflow preventer instead of your dual check valve. This extends up to the highest hazard possible, namely exposure to raw sewage, where the codes require the easily inspected and mechanical-failure-free protection provided by an air gap.

Answer 2

Well, anything can be a potential health hazard, including unpolluted dihydrogen monoxide. I suspect that this language is trying to say is:

• This valve prevents normal usage from backing up into the supply lines.
• This valve is not to be used when known serious health hazards are involved. Which might mean things like pipes going into refineries or chemical processing plants or nuclear power plants (you can never put too much water in a nuclear reactor) or similar.