Under the guidelines of a Cross-Connection Control Program a Backflow Preventer is required whenever a direct or in-direct cross-connection in a public or private water system exists. The Reduced Pressure Principle valve is designed for high hazard installation where back-pressure and back-siphonage could occur.
A fouled #1 check valve is the most common cause for this situation. Inspect the seal ring and seat for damage and debris, flush the system and re-assemble. For more information, refer to the installation instruction sheet.
The relief valve is fouled with debris. Inspect the seal ring and seat for damage and debris, flush the system and re-assemble. For more information, refer to the installation instruction sheet.
Inlet pressure fluctuations and/or water hammer downstream will cause the relief valve to discharge intermittently. A soft seated spring loaded check valve should protect the valve from water hammer. A pressure reducing valve or a check valve installed on the inlet should help minimize relief valve discharge caused by inlet pressure fluctuations.
If the drip point is high because of a low #1 check valve differential, inspect the #1 seat for debris, nicks in the seat profile and cracks from over-tightening. If the #1 differential is good, remove the relief valve cover and remove some of the lubrication on the upper plunger o-ring. Lastly, collapse the spring to solid height and re-assemble.
Make sure that there is a light amount of lubrication on the upper plunger o-ring and the cylinder bore in the relief valve cover is free from surface defects. Replace relief valve spring if necessary.
Inspect seal ring and seat for debris or surface defects. Flip the seal ring over or replace. Replace spring if necessary.
Collapse the spring to solid height and reassemble. Replace spring if necessary.
Inspect seal ring and seat for debris or surface defects. Flip the seal ring over or replace. Replace spring if necessary.
Collapse the spring to solid height and reassemble. Replace spring if necessary.
The difference between the actual #1 check valve differential and the relief opening point. 3 psi is the minimum buffer recommended. It should be noted that an assembly with less than a 3 psi buffer will provide the same level of protection as an assembly with 3 psi buffer.
As with any spring-loaded device, there is a reduction in pressure from the inlet side of a check valve and the outlet side. With an RPZ, you can expect to see anywhere from 8 to 13 psi of static pressure loss. The flowing pressure will also be lower so it's best to verify system pressure with a gage and review the head loss curves prior to installing an RPZ. It may be necessary to install a booster pump in systems with low supply pressures.
Downstream demand (gpm) will always be the overriding factor in sizing water control valves. Calculate the desired flows and the maximum allowable head loss. Review the head loss curves for the most appropriate size. Don't forget to consider an appropriate velocity (feet per second).
No! The majority of RPZ's on the market today cannot be installed in the vertical position. Most manufacturers have incorporated elbows between the gate valves and the main check valves to accommodate vertical risers. The Model 475V is approved for installations with vertical flow-up piping.
The relief valve stem assembly is guided by a machined piston bore in the cover of the relief valve. The "vent" hole is necessary to prevent a vacuum from being created as the relief valve travels from open to close.
Under a low downstream demand, a spring-loaded check valve tends to lift from one side first, but not completely off the surface of the seat. Turbulence in this area under this condition may lead to a vibration of the poppet against the seat. The valve may be oversized for the particular demands required.
The trick is to remove any water and pressure from the valve including the check valve areas as well as the relief valve. There are a number of ways to do this and each has it's merits. Refer to the instruction sheet on freeze-proofing (Doc # IS950&975FP) for more information.
The amount discharge depends on the amount of pressure within the system and the size of the fouling of the check valves. Refer to the "Relief Valve Discharge Rates" data sheet for further information on potential discharge rates.
An RPZ is designed for high hazard applications with a possibility of back-pressure in addition to back-siphonage. In the absence of a cross-connection control program a specifying engineer will determine if back-siphonage and back-pressure could occur within the system. Next he will determine if the installation presents a high hazard or a low hazard. If back-pressure and back-siphonage could occur and the installation is determined to be a high hazard, then the RPZ is necessary. If a cross-connection control program exists that governs the installation, consult local authorities for recommendations.
Yes, however, provisions for relief valve discharge (ie. Drain, sump pump, relief valve monitor switch, etc.) must be considered. Always consult local code requirements prior to installation. Under no circumstances should the assembly be allowed to be submerged.
Only a licensed and certified backflow tester with an approved differential pressure gage can test an RPZ. For information on how to become a certified tester, contact the Foundation for Cross-Connection Control and Hydraulic Research at the University of Southern California, ABPA or AWWA.
Installation, repair and maintenance procedures are included with every WILKINS RPZ, however, this should be reserved for a licensed, qualified plumber or specialist.
The answer is: What is the demand (gpm) downstream? On average, the RPZ has a 12 psi static loss across the two check valves. This means that it takes 12 psi to overcome the resistance of the check valves, however, it leaves you with 0 psi on the outlet. Therefore, the specifying engineer must calculate the required demand, refer to the headloss curves and confirm the need for a booster pump if pressures are too low. 20 psi will be the minimum in most situations.
Yes! Contact your WILKINS Sales Representative for pricing and availability.
You can't! A reduced pressure principle valve is not a pressure reducing valve.
Under the guidelines of a Cross-Connection Control Program a backflow preventer is required whenever a direct or in-direct cross-connection in a public or private water system exists. The reduced pressure detector assembly is designed for high hazard installations where back-pressure and back-siphonage could occur. Refer to the instruction sheet for more information.
They are identical in function, however, the RPDA has a metered by-pass line, equipped with a 3/4" RPZ to record any unauthorized water usage downstream.
3/4"
3/4" x 5/8"
WILKINS can provide a number of different water meters approved for use on the by-pass piping of all detector type backflow preventers, including remote read-out meters. Contact your WILKINS representative for pricing and availability.
Under the guidelines of a Cross-Connection Control Program a Backflow Preventer is required whenever a direct or in-direct cross-connection in a public or private water system exists. The Double Check Valve is designed for low hazard installations where back-pressure and back-siphonage could occur. Refer to the instruction sheet for more information.
The double check valve is similar to the RPZ except that there is no differential relief valve and the #1 and #2 check valve springs are identical in design. The DC must only be used to protect against a low hazard cross-connection.
A double check valve will function as designed when installed in the vertical flow-up position. Check with local authorities for installation and approval requirements.
Only a licensed and certified backflow tester with an approved differential pressure gage can test a DC. For information on how to become a certified tester, contact the Foundation for Cross-Connection Control and Hydraulic Research at the University of Southern California, ABPA or AWWA.
The trick is to remove any water and pressure from the valve including the check valve areas. There are a number of ways to do this and each has it's merits. Refer to the instruction sheet on freeze-proofing (Doc # IS950&975FP) for more information.
Under the guidelines of a Cross-Connection Control Program a Backflow Preventer is required whenever a direct or in-direct cross-connection in a public or private water system exists. The Double Check Detector Assembly is designed for low hazard installations where back-pressure and back-siphonage could occur. Refer to the instruction sheet for more information.
The DCDA is intended for installations which require metering for system leaks or unauthorized water usage. The DCDA includes a by-pass line which includes an approved water meter and an approved backflow preventer.
A Double Check Detector Assembly will function as designed when installed in the vertical flow-up position. Check with local authorities for installation and approval requirements.
A Double Check Detector Assembly will function as designed when installed in the vertical flow-up position. Check with local authorities for installation and approval requirements.
Under the guidelines of a Cross-Connection Control Program a Backflow Preventer is required whenever a direct or in-direct cross-connection in a public or private water system exists. The Pressure Vacuum Breaker is designed for high hazard installations where back-siphonage only could occur. These systems can be under continuous pressure and include a shut-off valve downstream. Refer to the instruction sheet for more information.
The cover of a PVB protects the air inlet seal from debris. The air inlet will discharge water if this seal is fouled with debris or if pressures drop below the float opening point. The seal may need to be replaced if excessive wear is noted. A brief discharge may also occur during system start-up and should cease when system is pressurized.
Only a licensed and certified backflow tester with an approved differential pressure gage can test a DC. For information on how to become a certified tester, contact the Foundation for Cross-Connection Control and Hydraulic Research at the University of Southern California, ABPA or AWWA.
Because the PVB is primarily an outdoor/irrigation device, freeze-proofing has become an important part of system maintenance. While there are many ways to accomplish this, freeze-proofing involves removing any pressurized water from the valve. Refer to the instruction sheet on freeze-proofing (Doc # IS720A&420FP) for more information.
Under a low downstream demand, a spring-loaded check valve tends to lift from one side first, but not completely off the surface of the seat. Turbulence in this area under this condition may lead to a vibration of the poppet against the seat. The valve may be oversized for the particular demands required.
Under the guidelines of a Cross-Connection Control Program a Backflow Preventer is required whenever a direct or in-direct cross-connection in a public or private water system exists. The Atmospheric Vacuum Breaker is designed for high hazard installations where back-siphonage only could occur. These systems cannot be under continuous pressure for more than 12 hours in a 24 hour period and prohibit the use of a shut-off valve downstream. Refer to the instruction sheet for more information.
The cover of a AVB protects the air inlet seal from debris. The air inlet will discharge water if this seal is fouled with debris or if pressures drop below the float opening point. The seal may need to be replaced if excessive wear is noted.
Because the AVB is primarily an outdoor/irrigation device, freeze-proofing has become an important part of system maintenance. While there are many ways freeze-proofing involves removing any pressurized water from the valve. Refer to the instruction sheet for more information.
The text book definition is a physical separation between the free flowing discharge end of a potable water supply pipeline and an open or non-pressure receiving vessel. An "Approved" Air Gap shall be at least twice the diameter of the supply pipe measured vertically above the overflow rim of the vessel, but, never less than 1/2".
Most manufacturers' offer an adapter that is designed for direct connection to the relief valve vent of an RPZ. This adapter is threaded on the outlet to allow for connection of an approved drain line. Because this constitutes a cross-connection, the adapter includes an approved Air Gap or physical separation. This fitting is available for all sizes of RPZ devices.
An air gap adapter fitting is designed to divert light, intermittent discharge from the relief valve vent to an approved drain. A fouled check can produce flows exceeding the adapter's capability, therefore, a properly sized drain should be installed to protect against water damage. Refer to the specification sheet which covers relief valve discharge rates.
Under the guidelines of a Cross-Connection Control Program a Backflow Preventer is required whenever a direct or in-direct cross-connection in a public or private water system exists. The Hose Connection Vacuum Breaker is designed for low hazard installations where back-siphonage only could occur. These systems cannot be under continuous pressure for more than 12 hours in a 24 hour period and prohibit the use of a shut-off valve downstream. Refer to the instruction sheet for more information.
A Hose Connection Vacuum Breaker is designed for installation on standard garden hose bibb shut-off valves. They are threaded directly to the hose bibb and include a vandal-proof set screw that prevents against un-authorized removal. Check with local codes for other installation requirements and always refer to the installation instruction sheet.
A manual drain feature is included on the Model BFP-8F specifically for installations requiring freeze protection.
Yes, however, there can be no shut-off valve attached to the end of the hose and it can not be elevated so as to create back-pressure.
A Single Check Valve is a device which prevents the flow of liquids in a direction reverse to the normal flow. There two types of seats: rubber and metal. The closure element can be internally spring-loaded to promote rapid and positive closure.
National standards and testing associations have developed design criteria for performance of a check valve. These criteria are applicable to backflow preventers and their operation. An "approved" check valve requires the closure element to be drip tight in the normal direction of flow when the inlet pressure is at least one (1) psi and the outlet is zero (0).
Under the guidelines of a Cross-Connection Control Program a Backflow Preventer is required whenever a direct or in-direct cross-connection in a public or private water system exists. The Single Check Valve is designed for low hazard installations where back-siphonage and back-pressure could occur.
A double check requires shut-off or isolation valves on the inlet and outlet for testing and maintenance of the check valves. In addition, 4 ball valve type test cocks are required to facilitate testing of the check valves. A dual check valve does not include any of these features, however, both contain "approved" check valves.
The DUC is not testable while the valve is installed. The checks must be removed and tested one at a time with a test kit specifically developed for the dual check valve. Installation may require testing to be done by a certified, licensed tester. For information on how to become a certified tester, contact the Foundation for Cross-Connection Control and Hydraulic Research at the University of Southern California, ABPA or AWWA.
Under the guidelines of a Cross-Connection Control Program a backflow preventer is required whenever a direct or in-direct cross-connection in a public or private water system exists. Laboratory and medical faucets can create in-direct cross-connections with hazardous materials, therefore, the requirement for a backflow preventer is justified.
Under the guidelines of a Cross-Connection Control Program a Backflow Preventer is required whenever a direct or in-direct cross-connection in a public or private water system exists. Hydronic heating systems utilize heated water from a potable water source for interior climate control. This heated water is considered non-potable and requires a backflow preventer between the water supply and the boiler.
A fouled check valve or relief valve is the most common cause for this situation. Inspect the seal rings and seats, flush the system and re-assemble. For more information, refer to the installation instruction sheet.
The vent located between the check valves is threaded for connecting a drain line. The drain line must terminate at an approved distance (air gap) above an approved drain. Refer to the installation instructions and local requirements.
An approved differential pressure gage is used to perform a predetermined amount of tests on a backflow preventer to verify compliance with national and local standards. The only instructions included with the kit are those used to test the DC, RPZ and the PVB.
Contact the factory for re-calibration instructions.
A certificate of calibration is included with all test kits upon completion of re-calibration from the manufacturer.
The valve setter transfers thrust downstream, thus eliminating the need for cement thrust blocks. Setters can reduce the amount of time and materials needed to install a backflow preventer.
The mechanical flange joint is designed with a stuffing box into which a rubber gasket is compressed by a ductile iron gland drawn up with steel bolts. It affords liberal deflection and allows expansion and contraction of the line without leakage.
Last revised June 21, 2005