Backflow Prevention valve

Backflow Prevention

Joe Stump, P.E., Utilities Manager

Office Hours: M - F, 8:00 AM - 4:00 PM
Accounting Office: 574-2290
Engineering Office: 574-2300


Backflow Prevention

Why is Backflow Prevention Needed?

Water normally flows in one direction, from the public water system through the customer’s cold or hot water plumbing to a sink tap or other plumbing fixture. The plumbing fixture is the end of the potable water system and the start of the waste disposal system.

Under certain conditions water can flow in the reverse direction. This is known as backflow. Backflow occurs when a backsiphonage or backpressure condition is created in a water line.

Backsiphonage may occur due to a loss of pressure in the water distribution system during a high withdrawal of water for fire protection, a water main or plumbing system break, or a shutdown of a water main or plumbing system for repair. A reduction of pressure below atmospheric pressure creates a vacuum in the piping. If a hose faucet was open and the hose submerged in a wading pool during these conditions, the non-potable water in the pool would be siphoned into the house’s plumbing and back into the public water system.

Backpressure may be created when a source of pressure, such as a pump, creates a pressure greater than that supplied from the distribution system. If a pump supplied from a non-potable source, such as a landscape pond, was accidentally connected to the plumbing system, the non-potable water could be pumped into the potable water supply.

Cross Connection is created when any link or channel between piping which carries potable drinking water and the piping or fixtures which carry non-potable water or other substances.

Non protected cross connections can cause contaminates to enter the drinking water system such as E.coli, Girdia, Cryptosporidium cyst and other Bacteria.

Where are Cross Connections Found?

Cross connections are found in all plumbing systems. It is important that each cross connection be identified and evaluated as to the type of backflow protection required to protect the drinking water supply. Some plumbing fixtures have built in backflow protection in the form of a physical air gap. However, most cross connections will need to be controlled through the installation of and approved mechanical backflow prevention device of assembly. Some common cross connections found in plumbing and water systems include:

1. Wash basins and service sinks.
2. Hose faucets.
3. Irrigation sprinkler systems.
4. Auxiliary water supplies.
5. Laboratory and aspirator equipment.
6. Photo developing equipment.
7. Processing tanks.
8. Boilers.
9. Water recirculation systems.
10. Swimming pools, hot tubs, landscape ponds.
11. Solar heat systems.
12. Fire sprinkler systems.

What Types of Backflow Assemblies are Available?

Pressure Vacuum Breaker Assembly (PVBA): PVBA’s must be installed at least 12 inches above the highest sprinkler that it serves but not higher than 5 feet above the ground. Control valves are allowed anywhere in the piping system. The PVBA must be installed with adequate room for testing and maintenance.

Atmospheric Vacuum Breaker (AVB): AVB’s must be installed at least 6 inches above the highest sprinkler that it serves but not higher than 5 feet above the ground. Control valves are not allowed downstream from the AVB. The AVB shall not be pressurized for more than 12 hours in any 24 hour period. If you have six sets on your sprinkler system you must have six control valves installed in front of six AVB’s. The AVB’s must be installed with adequate room for inspecting and maintenance.

Double Check Valve Assembly (DCVA): DCVA’s can be installed below ground in a vault or above ground not higher than 5 feet above ground. Control valves are allowed anywhere in the piping system. The DCVA must be installed with adequate room for testing and maintenance. If the DCVA is installed below ground sufficient drainage must be provided to prevent the assembly from being submerged.

The Double Check Valve Assembly is the most common backflow assembly used for sprinkler systems in the Yakima Valley.

Reduced Pressure Backflow Assembly (RPBA): RPBA’s are required on sprinkler systems if the system is connected to the drinking water and also any auxiliary water such as private wells or irrigation districts. RPBA’s must be installed above ground level and inspected before use by Yakima County. Irrigation water generally comes from open ditches and rivers. Contamination such as E.coli, Giardia, Cryptosporidium cyst and other Bacteria can enter the drinking water system from auxiliary water if it is not properly protected with an RPBA.

Backflow Prevention Standard Details

All Standard Details are provided in PDF format.


12.08.200 Cross-connections -- Prohibited -- Exception.

Cross-connections between the domestic water systems and other systems or equipment containing water and other substances of unknown or questionable safety are prohibited, except when and where suitable protective devices, as approved by the public works department, are installed, tested and maintained by the county to ensure proper operation on a continuing basis.
(Ord. 4-1985 Mod. 4 § 3.08, 1994)

1.028.210 Cross-connections -- Failure to remedy

Failure on the part of customers to discontinue the use of any and all cross-connections and to physically separate such cross-connections or install a suitable protective device when ordered to do so by the public works department will be sufficient cause for the discontinuance of water service to the premises on which the cross-connection exists and shall subject the customer to penalties as provided by Section 12.08.520.
(Ord. 4-1985 Mod. 4 § 3.09, 1994)

12.08.220 Cross-connections – Inspection

The county may make periodic inspections of premises served by the water supply to check for the presence of cross-connections. Any cross- connections found in such inspection shall be ordered removed and water service to the premises shall be discontinued until it is verified that the cross-connection has been removed.
(Ord. 4-1985 Mod. 4 § 3.10, 1994).

12.08.230 Air gap and flood level specifications for tanks

Air gap separation shall be an unobstructed vertical distance through the free atmosphere between the lowest opening from any pipe or faucet supplying water to a tank, plumbing fixture or other device and the flood level rim of the receptacle, and shall be at least double the diameter of the supply pipe measured vertically above the flood level rim of the vessel. In no case shall the gap be less than one inch.
(Ord. 4-1985 Mod. 4 § 3.11, 1994)

12.08.240 Double check valves.

Double check valves assembly shall be an assembly composed of two single, independently acting check valves, including tightly closing shutoff valves located at each end of the assembly and suitable connections for testing the watertightness of each check valve. Only Washington State Department of Health approved assemblies shall be accepted
(Ord. 4-1985 Mod. 4 § 3.12, 1994)

12.08.250 Reduced pressure principle backflow prevention device.

Reduced pressure principle backflow prevention device shall be a device incorporating two or more check valves and an automatically operating differential relief valve located between the two checks, two shutoff valves, and equipped with necessary appurtenances for testing. The device shall operate to maintain the pressure in the zone between the two check valves, less than the pressure on the water supply side of the device. At cessation of normal flow, the pressure between the check valves shall be less than the supply pressure. In case of leakage of either check valve, the differential relief valve shall operate to maintain this reduced pressure by discharging to the atmosphere. When the inlet pressure is two pounds per square inch or less, the relief valve shall open to the atmosphere, thereby providing an air gap in the device. Only Washington State Department of Health approved assemblies shall be accepted.
(Ord. 4-1985 Mod. 4 § 3.13, 1994).

12.08.260 Backflow prevention devices -- Installation location

Backflow prevention devices, where required, shall be installed at the meter or at a location designated by the public works director at the expense of the consumer. The device shall be located so as to be readily accessible for maintenance and testing, and where no part of the device will be submerged.
(Ord. 4-1985 Mod. 4 § 3.14, 1994).

12.08.270 Backflow prevention devices -- Situations requiring devices.

Backflow prevention devices shall be installed at the service connection or within any premises identified in Section 12.08.280 where, in the judgment of the public works director, the nature and extent of activities on the premises, or the materials used in connection with the activities, or materials stored on the premises may present an immediate and dangerous hazard to health should a cross- connection occur, even though such cross-connection does not exist at the time the backflow prevention device is required to be installed, including, but not limited to, the following situations:

(a) Premises having an auxiliary water supply:
(b) Premises having internal cross-connections that are not correctable; or intricate plumbing arrangements which make it impracticable to ascertain whether or not cross- connections exist;
(c) Premises where entry is restricted so that inspections for cross- connections cannot be made with sufficient frequency or at sufficiently short notice to assure that cross-connections do not exist;
(d) Premises having a repeated history of cross-connections being established or reestablished;
(e) Premises on which any substance is handled under pressure so as to permit entry into the public water supply, or where a cross- connection could reasonably be expected to occur. This shall include the handling of process waters and cooling waters;
(f) Premises where materials of a toxic or hazardous nature are handled such that, if back siphonage should occur, a serious health hazard may result.
(Ord. 4-1985 Mod. 4 § 3.15, 1994).

12.08.280 Backflow prevention devices -- Premises requiring.

The following types of facilities shall have a backflow prevention device installed as provided in Section 12.08.270 unless the public works director determines that no hazard will exist without said device:

(a) Hospitals, mortuaries, clinics
(b) Laboratories
(c) Piers and docks
(d) Sewage treatment plants
(e) Food or beverage processing plants
(f) Chemical plants using a water process
(g) Metal plating industries
(h) Petroleum processing or storage plants
(i) Radioactive material processing plants or nuclear reactors
(j) Others specified by the public works director.
(Ord. 4-1985 Mod. 4 § 3.16, 1994).

12.08.290 Backflow prevention devices -- Determination of type.

The type of protective device required shall depend on the degree of hazard which exists, as follows:

(a) An air gap separation or a reduced pressure principle backflow prevention device shall be installed where the water supply may be contaminated with sewage, industrial waste of a toxic nature, or other contaminant which would cause a health or system hazard;
(b) In the case of a substance which may be objectionable but not hazardous to health, double check valve assembly, air gap separation or a reduced pressure principal backflow prevention device shall be installed.
(Ord. 4-1985 Mod. 4 § 3.17, 1994).

12.08.300 Backflow prevention devices -- Standards and inspection.

(a) Backflow prevention devices shall be installed under the supervision of, and with the approval of, the county at the expense of the consumer.
(b) Backflow prevention devices shall be inspected and tested annually by the public works department or more often where successive inspections indicate repeated failure. The devices shall be repaired, overhauled or replaced whenever they are found to be defective. Inspections, tests and repairs and records thereof shall be done under the county's supervision at the expense of the consumer.
(Ord. 4-1985 Mod. 4 § 3.18, 1994)

12.08.310 Backflow prevention devices -- Termination of service for noncompliance.

Failure of the customer to cooperate in the installation, maintenance, testing or inspection of backflow prevention devices required in this chapter shall be grounds for the termination of water service to the premises or the requirements for an air gap separation and shall subject the customer to the penalties provided in Section 12.08.520.
(Ord. 4-1985 Mod. 4 § 3.19, 1994)