Bacflow manual

If you do not have it, you can download it for free. The Backflow Reference Manual can be downloaded and or printed on your printer by either complete Manufacturers chapter or individual model number within a chapter.

BAVCO can provide a free 3 ring binder with tabs for the various manufacturers to hold these printed pages. Should this Backflow Reference Manual stop short of your requirements, or if you have any further questions on any assembly please do not hesitate to contact our Customer Service Department at Or email us.

We would like to thank the many manufacturers for their help in making the information on the various assemblies available. All dimensions, specifications and breakdowns are produced by the manufacturers and the accuracy is solely the manufacturers responsibility, Assembly dimensions are approximate and may vary from actuals.

Skip to main content Skip to footer. Technical Reference PWS Parallel installations should be considered at those facilities where water service cannot be interrupted. Manifold installations may also be used on any water line larger than 10 inches. Assemblies shall not be installed in areas containing corrosive, toxic or poisonous fumes or gases which could render the assembly inoperable or pose a safety hazard to personnel.

Because of the inherent design of a reduced pressure backflow assembly, fluctuating supply pressure on an extremely low flow or static flow condition may cause nuisance dripping and potential fouling of the assembly. While not effective in all cases, the installation of a soft seated check valve immediately ahead of the RPZ will often hold the pressure constant to the assembly in times of fluctuating supply pressure.

Drainage Drainage for backflow prevention assemblies shall be provided for all installations of DCV or RPZ to accommodate discharge during testing or draining of the unit and for RPZ relief valve discharges, as follows: For RPZ devices, drainage capacity shall be sized to accommodate both intermittent discharges and a catastrophic failure of the relief valve. Refer to manufacturers flow curves to determine maximum discharge rate based on supply pressure or on-site pressure; whichever is greater.

Discharge from relief valves must be readily detectable to maintenance personnel either visually or by means of water level alarms, flow indicator lights, etc. All drainage from RPZ's must be by gravity drains. Sump pumps are not allowed unless they are sized to accommodate the maximum discharge rate and connected to emergency power supplies.

An air gap must be maintained between the RPZ relief valve opening and any discharge piping. The air gap must be at least twice the dimension of the effective opening of the relief valve; but in no case less than 1 inch. Manufacturer's air gap fittings may be utilized provided that they maintain a proper air gap and do not enclose or cover the relief valve. These fittings are only sized to handle intermittent and low flow discharges.

Additional drainage capacity may be required to accommodate a catastrophic relief valve failure. Discharge piping from relief valves shall be terminated a minimum of one inch above any floor drain or other receiving receptacle.

Discharge piping connected to a storm sewer shall be equipped with backwater check valve. Discharge piping connected to a sanitary sewer shall be trapped and equipped with a backwater check valve.

Discharge piping from pits or other structures must be terminated above grade in an area not subject to flooding generally one foot above the year flood elevation. The terminal end of the discharge piping must have a rodent screen and may need to be supported by a headwall. Flap valves should also be considered to prevent entry of cold air.

All exterior drains shall be kept free of snow during winter. Pit Installations Primarily due to considerations for access, safety and gravity drainage, it is preferred that backflow prevention devices not be installed in pits. With stairways, ladders or step irons. For crane access for installing and removing large assemblies. With adequate horizontal and vertical clearances to allow access to the device. With a full flow screened gravity drain terminating above grade for all RPZ installations as detailed in the drainage requirements.

With sump pumps or gravity daylight drains for all DCVA installations. With floors pitched to drain. With adequate ground cover to prevent freezing. With surface grading to divert runoff away from the entrance way. Semi-buried pits for berm installations may be necessary to satisfy gravity drainage requirements. All enclosures shall be designed: With a floor elevation that is at least 6 inches above finished grade.

To provide adequate clearances around the device to access the test cocks, shutoff valves, check valves and relief valve.

With electric heaters or heat trace wire for any water service used year round. With provisions for natural or artificial light. With full flow gravity drains according to the drainage requirements.

With security measures such as locking doors and panels, flow alarms or flow indictor lights, power indicator lights, etc. Installation Within a Building Where containment at the property line cannot be achieved or is waived based on extenuating circumstances, installation within a building is often desirable as the unit can be installed in a mechanical room or other area that has heat and light.

Above grade installations shall be provided with adequate clearances and discharge can be directed to floor or drains or through a sidewall above grade via screened louvers, scuppers, pipe sleeves with flap valves, etc. Below grade or basement installations are acceptable for DCVA's.

RPZ's are only allowed below grade where one or more of the following conditions can be met: Where an adequate gravity drainage system is provided to accommodate a relief valve failure.

Where water level alarms are installed to detect flow from the device and alert maintenance or security personnel. Where sump pumps are sized to accommodate a relief valve failure and are connected to emergency power. Where the floor area and volume below the device could accommodate discharge from a relief valve failure. For 2 inch and smaller units, 2, cubic feet is generally acceptable. Submission and Approval of Plans In accordance with Section 10 of the Cross Connection Control manual, the submission of plans and specifications for the installation of backflow prevention assemblies must include the following: A site plan to scale or with dimensions of the facility containing a general location map, name and address of facility, property lines, buildings, the size and location of public water main s and all fire and domestic water services, meter pits, yard piping and hydrants, pumper connection s , interconnections, and the location of the proposed backflow preventer s.

A plumbing floor plan plan view or partial floor plan indicating water services, name and address of facility, water meter layout, proposed backflow preventer s , booster pump system, floor drain s and all nearby objects examples: electrical panels, boilers, chillers, storage tanks, fire pumps, fire sprinkler risers, etc. The plan must be drawn to scale or with dimensions indicated from walls and all nearby objects.

A vertical cross section s of the proposed installation with elevations from floor, ceiling, outside grade and all nearby objects. All drawings must include the name and address of the facility, be stamped and signed by the designer and have a clear space for approval stamps. Engineer's Report An engineering report must be included with the plan submittal. Items that should be included or described in the report include: General use of water within the facility; Size and description of all fire and domestic water services; Number of floors within the facility Actul or estimated maximum flow demand; Pressures - existing and after the installation of the backflow preventer; Description of the fire fighting system - indicate the A.

Manual M class of sprinkler service; Description of the proposed installation of the backflow preventer — indicate the location of backflow preventer, drainage, lighting, heating, access to unit, square footage of the floor level where the backflow preventer is to be located; Description of the existing or proposed booster pump system, answering the following questions: After the installation of the proposed backflow preventer s , will the Net Positive Suction Head NPSH required for the proper operation of the booster pump system be adequate?

What is the pressure setting of the switch? An existing or proposed cutoff switch must be set at the following setting: For a cutoff switch where the backflow preventer is located upstream of the booster pump s - set at 10 psi. The need for dual backflow preventers. Does the facility need a continuous water supply?