14.6.1 Background
Unprotected cross-connections to the potable water system can result in mild changes to the aesthetic quality of the water affecting taste, odor and color to severe changes which can result in illness or death. The purpose of a cross-connection control program is to identify these connections and provide appropriate protection.
14.6.2 Introduction
Use this outline to either develop a comprehensive cross-connection control program or to update and maintain an existing program.
14.6.3 Cross-connection Survey
One of the first steps in developing a cross-connection control program is to conduct a thorough survey of the potable water system to identify all actual or potential cross-connections. While an initial survey of the vessel can be time consuming it is essential to ensure that all connections are identified so that appropriate protection can be decided upon.
Protection of potable water can take two forms: containment or complete protection. While the former may be the objective for a water supplier and requires less time and detail for this guidance the latter will be our objective.
To illustrate the following example is provided: A surveyor enters a structure and identifies numerous connections to the potable water, both non-health-hazard and health-hazard connections. For containment purposes an RP assembly on the exterior supply line downstream of the water meter would contain all of the hazards within the structure but would do nothing to protect the individual connections within the facility. If complete protection is the goal each cross-connection in the structure must be identified and a decision made as to the appropriate backflow prevention method to be used. For vessels under the VSP complete protection is the goal.
Surveyors should be
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knowledgeable in basic plumbing
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knowledgeable in the principles of backflow to include backsiphonage and backpressure.
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Able to identify both potential and actual cross-connections
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Familiar with the level of hazard posed by each connection
Surveyors should physically inspect all areas of the vessel that are supplied with potable water. The best approach for this may be to go deck by deck, starting with the decks that have connections which pose the greatest risk to health. This may require starting with the engine room deck. As each connection is identified they are added to a listing. All of the information related to this connection should also be added to the listing. An example of required information can be found later in this outline. Connections that are found to be unprotected or inadequately protected must be addressed as quickly as possible especially if the connection is a health hazard.
14.6.4 Backflow Protection Methods
All graphics provided courtesy of the United States Environmental Protection Agency (USEPA)
14.6.4.1 Nonmechanical Backflow Protection
Air-gap
Antisiphon loop
Atmospheric vacuum breaker
Hose-bib vacuum breaker
Double check with atmospheric vent
Pressure vacuum breaker
Reduced pressure principle assembly
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14.6.5.1 List of connections requiring backflow prevention on vessel.
A log listing of all cross-connections on the vessel must be developed. At a minimum the log should contain the data elements listed in columns 2, 3, 6, 7, and 8. The inclusion of the additional data listed below is recommended.
Deck (A, B, C 1,2,3..)
1
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Location (of connection and of device, if different)
2
|
Connection Description (e.g., hose, chemical tank, coffee machine, detergent dispenser)
3
|
Connection subjected to Continuous Pressure (CP) or Noncontinuous Pressure (NCP)
4
|
Connection Subjected to (Backsiphonage only) or (Backsiphonage and Backpressure)
5
|
Protection Used (air- gap or manufacturer name and designation for device)
6
|
Inspection Date
7
|
Inspection Results (passed, replaced, psi results)
8
| 14.6.5.2 Specific Backflow Protection Choices on Vessel: Air-gaps and backflow prevention devices
Use this section to provide information to vessel staff on the specific backflow prevention devices used on the vessel. For each device a copy of the specification sheets or technical sheets as well as the manufacturer’s installation recommendations should be included in the program documentation file. Generally these documents are available online from the websites of each device manufacturer.
Manufactured air-gaps Manufacturers specification sheets -
Non-continuous pressure devices Atmospheric Vacuum Breaker -
Manufacturer’s installation recommendations Hose Vacuum Breaker Manufacturers specification sheets Manufacturer’s installation recommendations Select double check devices with intermediate vents (such as Watts NLF9) Manufacturers specification sheets Manufacturer’s installation recommendations Continuous pressure devices (such as Watts N9) Select double check valve with intermediate vent Manufacturers specification sheets Manufacturer’s installation recommendations Pressure vacuum breaker Manufacturers specification sheets Manufacturer’s installation recommendations Test kit and instructions Reduced pressure principle assembly Manufacturers specification sheets -
Test kit and instructions
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