4
MAINTENANCE MANUAL MODELS 825Y, 825YA, 825, 825D, 825YD & 826YD
Freeze Protection
Procedure
The reduced pressure backflow prevention assembly is subject to
damage if the internal water is allowed to freeze. It is suggested
that all assemblies be installed with resilient seated shutoffs so
that a drip tight closure can be achieved to prevent refilling of
the assembly after the freeze protection procedure is performed.
The unit must be protected from freezing by a heated enclosure,
draining, insulation using heat tape, or other suitable means.
However, the unit must always be accessible for testing and
maintenance. If the system will be shut down during freezing
weather, use the following procedure to
drain internal passages.
The Model 825YA can be removed from
the line as a winterizing procedure. See
Figure 5 for proper ball valve procedure.
Model 825Y (
3
/
4
–2") Reduced
Pressure Zone and Relief
Valve Freeze Protection
1. Slowly close the main shutoff valve upstream
of the assembly, which provides water to the system.
2. Drain system water upstream of the first check
by means other than through the assembly.
Check Valve Draining Procedure
3a. First check (zone) Open #2 and #3 test cocks. All water
between the first and second check valves will drain through
the relief valve port.
3b. Second check (downstream)—Remove the second check
cap, spring and disc holder. All water downstream of the
second check (that is higher than the outlet shutoff valve) will
drain through the body.
Relief Valve Draining Procedure
4a. If device is equipped with optional drain plugs, remove plugs
in the relief valve cover and body. Open #2 and #3 test cocks.
All water will drain through plug holes.
4b. For standard models (not equipped with optional drain plugs)
loosen the relief valve cover and allow water to drain from
both sides of the diaphragm.
Ball Valve ShutOff Draining Procedure
5a. If the assembly has been installed with ball valve shutoff
valves, they must also be properly drained to prevent freeze
damage. After draining procedure has been completed on the
backflow prevention assembly, position all ball valve shut-offs
and test cocks in a half open/half closed (45 degree) position.
(see Figure 5)
5b. Open the ball valve approximately 45 degrees while draining
the pipeline and assembly to allow water between the ball
and valve body to drain. Leave the ball valve in this position
for the winter to prevent freeze damage.
5c. The ball valves must be fully closed before the system is
repressurized. OPEN AND CLOSE BALL VALVES SLOWLY
TO PREVENT DAMAGE TO THE SYSTEM CAUSED BY
WATER HAMMER.
Model 825, 825D and 825YD (2
1
/
2
–10")
Reduced Pressure Zone and Relief Valve
Freeze Protection
1. Slowly close supply valve within freeze protected area, open
air bleed valves on No. #1 check valve and relief valve (3
places), and open No. #2 and #3 test cocks. Water within the
zone will be drained to the lowest point of the relief valve
discharge port (relief valve seat). A minor amount of water will
remain in the bottom of the valve body, but this is not suffi-
cient to cause freezing damage.
2. With this procedure, about one-half of the relief valve will be
drained. To drain the relief valve on Models 825 and 825D,
loosen the relief valve cover bolts and allow the relief valve to
drain. Retighten bolts before repressurizing system. To drain
relief valve on Models 825YD, open the two air bleeds (one
on the body, the other on the cover), then remove drain plugs.
Replace drain plugs before repressurizing system.
3. The system design must provide a means for draining
upstream of the #1 check valve and downstream of the #2
check valve. Test cocks #1, #2, and #4 and the air bleed valve
on #2 check valve may be opened to allow air to enter to
assist in draining. Depending on system design, these sec-
tions should be able to be drained to the pipe centerline.
4. Position the assembly shutoff valves and test cocks in the
half open/half closed position to allow complete draining
of the assembly shutoff valve bodies and test cocks.
5. Some units contain a drain plug in the bottom of the second
check body. Open test cocks and remove plug to drain.
Figure No. 5
