Hazard Assessment & Protection Selection
High hazard vs low hazard classification, containment vs isolation, and matching protection to risk level.
- Classify cross-connections as high hazard or low hazard based on the substance involved
- Distinguish between containment and isolation protection strategies
- Identify the correct assembly for boiler, irrigation, and fire line scenarios
- Explain the difference between contamination and pollution in backflow terms
- Apply the degree of hazard to select minimum protection levels
Leçon 1
High Hazard vs Low Hazard Classification
Degree of Hazard
Every cross-connection is classified by the degree of hazard - the potential health risk posed by the substance that could backflow into the potable water supply. This classification determines the minimum level of backflow protection required.
High hazard (contamination) - A substance that could cause illness or death if ingested. High hazard cross-connections require the highest level of protection: an RPZ assembly or an air gap.
Low hazard (pollution) - A substance that is objectionable but not a health threat. Low hazard substances affect the taste, odor, or appearance of water but would not cause illness. Low hazard cross-connections may be protected with a DCVA or higher.
High Hazard - Contamination
Boiler systems with chemical treatment
Medical facilities - hospitals, labs, dialysis
Chemical plants and industrial processes
Irrigation with chemical injection (fertilizer, pesticide)
Mortuaries and funeral homes
Sewage treatment connections
Low Hazard - Pollution
Fire sprinklers with no additives (stagnant water only)
HVAC cooling towers without chemical treatment
Irrigation without chemical injection
Food-grade beverages - soda dispensers
Swimming pools (chlorinated but non-toxic levels)
The Gray Areas
Some cross-connections seem straightforward but require careful evaluation. For example:
- A swimming pool is generally a low hazard unless chemical feed equipment is directly connected to the potable supply
- A boiler under 15 psi with no chemical treatment may be classified as low hazard in some jurisdictions, but a boiler with chemical treatment is always high hazard
- An irrigation system is low hazard unless it has a chemical injection port (fertilizer, herbicide, or pesticide injection), which makes it high hazard
Exam Rule of Thumb
If the substance could make someone sick or cause death, it is high hazard and requires an RPZ or air gap. If it only affects taste, odor, or appearance, it is low hazard and a DCVA is the minimum. When in doubt, the exam expects you to protect to the higher hazard level.
Hazard assessment in practice - what to look for:
When performing a site survey, document:
- All potable water supply connections in the building
- Any equipment, process, or system connected to the water supply that could introduce contaminants
- The nature of each substance in connected systems (chemical names, MSDS if available)
- Whether each cross-connection already has a backflow prevention device installed
- Whether existing devices are the correct type for the hazard level
Recategorization scenarios:
A cross-connection may need to be recategorized if:
- A fire sprinkler system that was originally installed without additives later has antifreeze added (recategorizes from low hazard to high hazard)
- An irrigation system adds chemical injection equipment (recategorizes from low hazard to high hazard)
- A boiler system changes from untreated water to chemically treated water
The cross-connection control surveyor or the water utility must be notified when these changes occur so the protection level can be upgraded.
High hazard (contamination) means the substance could cause illness or death and requires an RPZ or air gap. Low hazard (pollution) means the substance is objectionable but not dangerous and requires a DCVA at minimum. Always classify to the higher hazard level when uncertain. Recategorize cross-connections when the downstream system changes (e.g., antifreeze added to fire sprinklers).