Cross Connections

September 29-30, 2011

Drinking Water ProgramSustained Compliance Workshop

Lee Johnson, P.E.lee.johnson@alaska.gov

907-451-2179

ObjectivesWhat is a Cross Connection?How are they regulated?What is a Back Flow Preventer?Types of PreventersExamples of Cross Connections

What is a Cross Connection? Defined in 18 AAC 80.1990(a)(36)

Basically it is an ACTUAL or POTENTIAL physical connection or arrangement between otherwise separate piping systems containing potable water and any contaminant, whereby water may flow between the two systems.

Backflow – Two Types

Back Pressure: Pressure of nonpotable fluid is greater than pressure of potable water.

Back Siphonage: Negative pressure in potable water piping causes nonpotable fluid to be siphoned into potable water line.

High or Low HazardLow Hazard - will not have an immediate

effect on health, but could have an impact on the potable water.

High Hazard - will cause an immediate toxic effect or cause immediate and severe illness.

Cross Connections Are Prohibited18 AAC 80.025(a) A person may not construct, install, or use a cross connection in a public water system, or allow a water system that contains a cross-connection to connect to a public water system.

18 AAC 80.025(b) If the department determines that a facility has the potential to contaminate public water system through backflow, the owner or operator of the public water system shall install, maintain, and test on the service line to and at other locations in that facility, a backflow prevention device that conforms to ANSI/AWWA Standards C510-97, Double Check Valve Backflow prevention Assembly, or C511-97, Reduced-Pressure Principle Backflow Prevention Assembly, adopted by reference in 18 AAC 80.010(b).

18 AAC 80.025(b) continuedThe owner or operator of the public water system may delegate the installation, maintenance, and testing of the backflow prevention device to the owner or operator of the facility that poses the risk. This delegation does not relieve the owner or operator of the public water system of the responsibility to install, maintain, and test the backflow prevention device.

Statutes & CodesAlaska Statutes:

Article 8 Section 18.60.705 Portions of Uniform Plumbing Code – 2009

adopted by reference, 18 AAC 80.010(c)UPC Chapter 6

Section 603 pertains to Cross Connections

Table 6-2 Backflow Prevention Devices, Assemblies, and Methods

Service Connections and Premise Plumbing

Drinking water program regulates water systems – Sources , treatment, and distribution systems, not service connections.

There is risk within a building from cross connections even if distribution system is protected. Plumbing Code

What about cross connections within your facility?

Need to protect potable taps from nonpotable use taps within water plant.

Plan Review & Sanitary SurveyDuring engineering plan reviews we look for

Cross Connections within the public water system, the treatment plant, and the water distribution system.

BUT…….. For existing systems the sanitary survey process is the only other opportunity for staff or inspectors to look for and ask questions about facilities connected to the distribution system?

Also – Systems and plants are often modified through routine maintenance resulting in new cross connections or elimination of backflow prevention.

Owners, Operators, and Surveyors Should Consider:

Types of facilities connected to drinking waterdistribution system (Actual or Potential Hazards?):

Health ClinicsHospitalsSchoolsWater and Wastewater Treatment plantsMortuariesOther

Others?What other potential or actual cross

connections can you name?

Direct vs Indirect

Devices and AssembliesDevice -- cannot be tested

Assembly -- has two isolation valves and has test cocks for proper testing of the backflow prevention assembly

Backflow Prevention

Air Gap2 Pipe Diameters or 1 inch minimum

RPZReduced Pressure Zone Assembly

DCDouble Check Valve Assembly

PVBPressure Vacuum Breaker

AVBAtmospheric Vacuum Breaker

Backflow PreventionPrevents

Backsiphonage LOW & HIGH HAZARDProper Air GapAtmospheric

Vacuum BreakerPressure Vacuum

BreakerReduced Pressure

Zone BFPDouble Check Valve

(low hazard only)

Prevents BackpressureLOW HAZARDProper Air GapDouble Check Valve

HIGH HAZARDProper Air GapReduced Pressure

Zone BFP

Insert New table 6-2

Air Gap

Flow condition

Non flow condition

Atmospheric Vacuum Breaker

Protection

EXAMPLE AIR GAPS

Tank

Air Gap

POTABLESUPPLY

PUMP

FLOAT

NONPOTABLEAPPLICATION

Hose Bibb Vacuum Breaker

Pressure Vacuum Breaker

TEST PORTS

NORMAL FLOW

Double Check Valve

FLOW DIRECTION

#1 GATE VALVE

#2 CHECK VALVE

Reduced Pressure Zone Backflow Prevention Assembly (RPZ)

TEST PORTS

PRESSUREDIFFERENTIALRELIEF VALVE

#2 CHECK VALVE

#1 CHECK VALVE

#2 GATE VALVE

High hazard condition

RPZ

RPZ

RPZ – Proper Installation?

RPZ

Proper Installation?

Pumping Station Cross-connections

Priming of raw water pumps with finished water.Air relief valves piped directly to a drain.

• Cooling water for an emergency generator submerged in a drain or returned to the potable supply.

GATE VALVE

FLOOR DRAIN

AIR VACUUM RELEASE

SILENT CHECK

Treatment Bypass Piping

Emergency Bypass

Emergency Bypass Installed

Filter Bypass Piping

Bypass Piping

Disinfection Bypass Piping

Water Meter as Cross Connection?

Submerged Inlet

Surface Wash Arms

Surface Wash Arm – Pressure Filter

Backwash Waste Lines

Softener Backwash Waste Line

Air Gap

UV and Cross Connections?

Treatment Plant Lab Sink

Distribution System• Direct connections to sewers for flushing either the

water main or sewer.

Distribution Issues

RESOURCES• Alaska Drinking Water Regulations

• 18AAC 80.025• American Water Works Association

• Recommended Practice for Backflow Prevention and Cross Connection Control – M14

• EPA’s Cross Connection Control Manual• Uniform Plumbing Code

•Chapter 6• Kenneth Kerry

• Water Distribution System O&M Manual• USC Foundation for Cross-Connection Control and Hydraulic Research•Lots of internet resources

Questions?