FEATURES AND OPERATING PROCEDURES
This device consists of two independently operating poppet type check valves. Each check valve is spring loaded to maintain a minimum
of 1 PSIG differential pressure across the check in a no-flow condition. In a normal flow condition the checks open an amount correspond-
ing to the flow rate. During a backflow (backpressure) situation the seat discs close and seal to prevent any flow reversal. Sizes 2
1
/
2
"
through 10" (805YD) include two spring loaded Y-pattern check valves with epoxy coated ductile iron bodies and bronze trim, two cast iron
shut-off valves and four testcocks for field testing. All valves are flanged type and the unit is shipped completely assembled.
The Model 806YD device consists of a mainline double check valve with a metered
3
/
4
" by-pass double check valve connected around
the mainline checks. The mainline pressure drop is slightly higher than the by-pass, thus all small flow up to the crossover point (approx.
9 GPM) is through the by-pass. Above the crossover point flow is through the mainline and the by-pass.
The FEBCO 806YD Device main line unit consists of two independent, spring loaded, Y-pattern check valves, two shutoff valves
and four testcocks. The spring loaded poppets in conjunction with soft elastomer discs provide drip tight closure against backflow. The
Y-pattern valve design provides low pressure loss at the high flow rates. The shutoff valves are OS&Y type, UL listed for fireline service.
The by-pass line assembly consists of a water meter in series with a Model 805YB
3
/
4
" double check valve. The meter is the total type
with accurate registration between 1 and 20 gpm flow rates. The static pressure drop across both checks is approximately 2 PSI less
than the mainline check valves.
Consult local codes before installing any Backflow Prevention assembly.
GENERAL SERVICE PROCEDURES (General service instructions applicable to all sizes.)
1. Rinse all parts with clean water prior to assembly.
2. DO NOT USE ANY PIPE DOPE, OIL, GREASE OR SOLVENT ON ANY PARTS unless instructed to do so.
4. Do not force parts. Parts should fit freely together. Excess force may cause damage and render the device inoperable.
5. Carefully inspect seals, seating surfaces, etc. for damage or debris.
5. Test unit after servicing to insure proper operations.
6. Refer to applicable parts list and figures for more information.
7. A table on the back page provides size and material information for standard parts (non-special design). These parts can usually be
purchased locally from parts distributors, rather than special order from the factory.
8. Some water conditions can cause a buildup of calcium or similar material deposits on some moving parts. Normally this condition
would not occur on devices used in systems with varying flow rates. The scraping action of moving parts helps to remove any deposits.
However, with devices used on static systems such as firelines, any deposits would not be scraped away and could interfere with the
check valve operation. Devices in these applications should be disassembled and inspected on a periodic basis depending on water
quality. Any deposits should be removed from the center guiding stem and bushings. Use care to avoid damage to guiding surfaces.
TESTING
All mechanical devices should be inspected on a regular basis to ensure they are working correctly. The assembly should be tested
at time of initial installation, after servicing or maintenance, and at least annually thereafter. Acceptable test procedures are published by
Foundation for Cross Connection Control and Hydraulic Research at the University of Southern California (USC), The American Water
Works Association (AWWA), The American Society of Sanitary Engineering (ASSE Series 5000) and the Canadian Standards Associa-
tion (CAN/CSA B64•10). Please consult the regulatory authority in your area for more specific information.
FEBCO Operation and Maintenance
805YD / 806YD
Double Check and Double Check Detector Assembly (2
1
/
2
" – 10")
805YD
(Shown with OS&Y Shut-offs)
806YD
FEBCO Model 805YD & 806YD (2
1
/
2
" - 10")
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