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MAINTENANCE MANUAL MODELS 825Y, 825YA, 825, 825D, 825YD & 826YD
Feature and Operating Procedures
FEBCO manufactures several models of Reduced Pressure Backflow
preventers. The Model 825Y and 825YA are available in sizes 3/4–2"
with bronze body and cover as standard. Other materials are avail-
able. The FEBCO Model 825 sizes 21/2–10" were manufactured with
cast iron. The FEBCO Model 825 Type D and 825 Type YD sizes
21/2"–10" are manufactured with standard body material of ductile
iron.
The FEBCO Reduced Pressure Backflow preventer assembly con-
sists of two independently operating, spring loaded check valves
with a pressure differential relief valve located between the two
checks. The pressure drop across the first check valve is approxi-
mately 6.0 psid with no flow. The relief valve consists of a hydrauli-
cally balanced diaphragm with the high pressure side hydraulically
connected to the upstream side of the first check. The low pres-
sure side is hydraulically connected to the reduced pressure zone,
thus the relief valve remains closed during normal operation. The
low pressure side of the diaphragm is spring loaded to force the
relief valve open when the pressure drop across the first check (and
across the diaphragm) reduces to approximately 2.5 psid. A com-
plete assembly includes two shut-off valves and four test cocks.
Example sectional views below show typical components and flow
passages with corresponding pressure readings (no flow conditions)
at the various locations within the assembly.
Reduced Pressure Backflow Preventer
*Relief Valve
Rotated 90º for Clarity
Model 825Y (
3
/
4
–2")
Figure No. 1
Model 825YD (2
1
/
2
–10")
Figure No. 2
Inlet Shutoff
Outlet Shutoff
First Check
Second Check
100 PSI
93 PSI
Relief Valve*
Reduced
Pressure
Zone
*Relief Valve
Rotated 90º for Clarity
94
PSI
94 PSI
Inlet Shutoff
Outlet Shutoff
First Check
Second Check
100 PSI
93 PSI
Relief Valve*
