Specialty Plumbing, Potable Water Protection, and Cross-Connection Control
Backflow Fundamentals
Cross-connection control is the highest-value topic in this domain. A cross connection is any actual or potential link between potable water and a contamination source. Protection methods rank from best to least: an air gap, then a reduced-pressure principle assembly, then a double check valve assembly or pressure vacuum breaker depending on the hazard, then a dual check or atmospheric vacuum breaker for low hazards. High hazards (sewage, chemicals, boiler treatment, irrigation with injectors) require an air gap or an RPZ. Every testable assembly must be tested at installation and annually by a certified tester, with records kept.
Specialty Systems to Expect
- Medical and dental equipment, laboratory faucets, and aspirators, where air gaps and vacuum breakers protect the supply.
- Boilers and hydronic systems, which need makeup water protection.
- Irrigation and hose bibbs, which require backflow protection and vacuum breakers.
- Rainwater, greywater, and reclaimed water systems, which must be separated, labeled, and identified by purple pipe.
- Carbonators and beverage equipment, which need protection against carbon dioxide backflow.
Traps in Questions
- Treating a hose-bibb vacuum breaker as a full backflow preventer for a high hazard.
- Placing a backflow device where it can be submerged or where it drains into a sewer.
- Forgetting that a pressure vacuum breaker cannot be installed subject to backpressure.
- Skipping the annual test or the certified tester requirement.
Rule of Thumb
Identify the hazard first: if the contaminant can cause illness or death, use an air gap or RPZ. If the hazard is only a nuisance, a double check or vacuum breaker may be acceptable.