Hazard Assessment for a Hospital Dialysis Unit With Multiple Cross-Connections
A hospital dialysis unit has several water connections: a reverse-osmosis (RO) unit fed from a dedicated domestic line, a bicarbonate mixing station with a hose bib, a waste drain line that receives dialysate, and a portable cleaning cart that connects to a hose station. The RO unit has a booster pump that can raise pressure to 90 psi, while the domestic supply is 60 psi. The hose bib at the bicarbonate station is fitted with a screw-on hose and a spray nozzle, and the hose can reach the floor drain. The cleaning cart hose station is used with a bucket and a submerged inlet. The facility has no backflow prevention assemblies on these branches, relying on air gaps at the RO unit and the drain. A survey is being conducted to determine protection requirements.
1. Classify the hazard level for each connection and determine which connections require an air gap or an RPBA versus a double check.
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The RO unit is a health-hazard connection because the RO feed line can be exposed to dialysate and because the booster pump can create backpressure above the domestic supply pressure. The air gap at the RO unit is acceptable only if it is a true air gap with the required separation and is not subject to backpressure; if the booster pump can pressurize the RO feed line, an RPBA is needed on the domestic branch. The bicarbonate mixing station hose bib with a screw-on hose and spray nozzle is a health hazard because the hose can be submerged in the floor drain or in bicarbonate solution, creating a backsiphonage path. A hose bib vacuum breaker is not sufficient for a health hazard with a submerged inlet; an RPBA or an air gap is required. The cleaning cart hose station with a submerged inlet is also a health hazard and requires an air gap or an RPBA. The waste drain line is a health hazard, but it is protected by the air gap at the drain, which must be maintained and inspected. The double check valve assembly is not appropriate for any of these health-hazard connections. The survey should recommend RPBA or air gap protection on the RO feed, the bicarbonate station, and the cleaning cart station, and should verify the drain air gap.
2. The facility argues that the air gaps already provide protection and that no additional assemblies are needed. Evaluate this position and identify the specific deficiencies.
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The air gaps provide protection only at the points where they are correctly installed and maintained. The air gap at the RO unit does not protect the domestic line upstream of the RO unit from backpressure created by the RO booster pump; if the pump can raise pressure to 90 psi against a 60 psi supply, the domestic line can be pressurized. The air gap at the drain protects the drain, not the hose bib or the cleaning cart station. The hose bib with a screw-on hose and spray nozzle is a classic backsiphonage hazard because the hose can be submerged, and the spray nozzle can create a siphon. The cleaning cart with a submerged inlet is likewise unprotected. The facility's position is therefore incorrect. The specific deficiencies are: no protection on the RO feed against backpressure, no protection on the bicarbonate hose bib, no protection on the cleaning cart hose station, and no verification that the drain air gap is maintained at the required dimension. The survey should require RPBA or air gap protection at each health-hazard connection and should establish a testing and inspection schedule.