Watts 757NDCDA User Manual
For Non-Health Hazard Applications
ES-757DCDA/757NDCDA
Job Name
Job Location
Engineer
Approval
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Series 757DCDA,
757NDCDA
Double Check Detector Assemblies
Sizes: 21/2" – 10" (65 – 250 mm)
Series 757DCDA, 757NDCDA Double Check Detector
Assemblies are used to prevent backflow of non-health hazard
pollutants that are objectionable but not toxic, from entering
the potable water supply system. The 757DCDA, 757NDCDA
may be installed under continuous pressure service and may
be subjected to backpressure and backsiphonage. Series
757DCDA, 757NDCDA is used primarily on fire line sprinkler
systems when it is necessary to monitor unauthorized use of
water.
Contractor
Approval
Contractor’s P.O. No.
Representative
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757DCDAOSY
Features
• Extremely compact design
• 70% Lighter than traditional designs
• 304 (Schedule 40) stainless steel housing & sleeve
• Groove fittings allow integral pipeline adjustment
• Patented tri-link spring check provides lowest pressure loss
• Unmatched ease of serviceability
• Available with grooved butterfly valve shutoffs
• May be used for horizontal, vertical or N pattern installations
• Replaceable check disc rubber
Specifications
The Double Check Detector Assembly shall consist of two
independent tri-link check modules within a single housing,
sleeve access port, four test cocks and two drip tight shutoff
valves. Tri-link checks shall be removable and serviceable, without the use of special tools. The housing shall be constructed
of 304 Schedule 40 stainless steel pipe with groove end connections. Tri-link checks shall have reversible elastomer discs
and in operation shall produce drip tight closure against reverse
flow caused by backpressure or backsiphonage. The bypass
assembly shall consist of a meter, which registers in either gallon or cubic measurement, a double check backflow assembly
and required test cocks. Assembly shall be a Watts Regulator
Company Series 757DCDA, 757NDCDA.
757DCDABFG
757NDCDAOSY
Watts product specifications in U.S. customary units and metric are approximate and are provided for reference only. For precise measurements,
please contact Watts Technical Service. Watts reserves the right to change or modify product design, construction, specifications, or materials without prior notice and without incurring any obligation to make such changes and modifications on Watts products previously or subsequently sold.
Available Models
Suffix:
OSY – UL/FM outside stem and yoke resilient
seated gate valves
BFG – UL/FM grooved gear operated butterfly valves
with tamper switch
*OSY FxG – Flanged inlet gate connection and grooved outlet
gate connection
*OSY GxF – Grooved inlet gate connection and flanged outlet
gate connection
*OSY GxG – Grooved inlet gate connection and grooved outlet
gate connection
Available with grooved NRS gate valves - consult factory*
Post indicator plate and operating nut available - consult factory*
*Consult factory for dimensions
Materials
Housing & Sleeve: 304 (Schedule 40) Stainless Steel
Elastomers: EPDM, Silicone and Buna-N
Tri-link Checks: Noryl
®
, Stainless Steel
Check Discs: Reversible Silicone or EPDM
Test Cocks: Bronze Body Nickel Plated
Pins & Fasteners: 300 Series Stainless Steel
Springs: Stainless Steel
Pressure — Temperature
Temperature Range: 33°F – 140°F (0.5°C – 60°C)
Maximum Working Pressure: 175psi (12.1 bar)
Approvals
Dimensions — Weight
C (open)
D
A
1048 B64.5
H
G
(BFG & OSY only)
J
I
P
757DCDA , 757NDCDA
SIZE (DN) DIMENSIONS WEIGHT
A C (OSY) D G H I J P 757DCDA 757NDCDA
in. mm in. mm in. mm in. mm in. mm in. mm in. mm in. mm in. mm lbs. kgs. lbs. kgs.
21⁄2 65 31 787 163⁄8 416 31⁄2 89 291⁄16 738 211⁄2 546 151⁄2 393 813⁄16 223 133⁄16 335 139 63 147 67
3 80 31
4 100 33
6 150 44 1118 30
8 200 50 1270 373⁄4 959 611⁄16 170 541⁄8 1375 405⁄8 1032 277⁄16 697 1511⁄16 399 213⁄16 538
10 250 571⁄2 1461 453⁄4 1162 83⁄16 208 66 1676 50 1270 321⁄2 826 175⁄16 440 24 610
11
⁄16 805 187⁄8 479 311⁄16 94 301⁄4 768 221⁄4 565 171⁄8 435 93⁄16 233 141⁄2 368 159 72 172 78
1
⁄2 851 223⁄4 578 4 102 33 838 231⁄2 597 181⁄2 470 915⁄16 252 153⁄16 386 175 79 198 90
1
⁄8 765 51⁄2 140 443⁄4 1137 333⁄4 857 233⁄16 589 131⁄16 332 19 483
309 140 350 159
494 224 569 258
795 361 965 438
C
D
A
757DCDABFG , 757NDCDABFG
SIZE (DN) DIMENSIONS WEIGHT
A C D G
in. mm in. mm in. mm in. mm in. mm in. mm in. mm in. mm in. mm lbs. kgs. lbs. kgs.
21⁄2 65 271⁄2 698 8 203 31⁄2 89 297⁄8 759 211⁄2 546 1415⁄16 379 813⁄16 223 13 330
3 80 28 711 85⁄16 211 311⁄16 94 3011⁄16 779 221⁄4 565 157⁄16 392 93⁄16 233 131⁄2 343
4 100 283⁄4 730 815⁄16 227 311⁄16 94 3115⁄16 811 231⁄2 597 161⁄4 412 915⁄16 252 14 356
6 150 37 940 10 254 5 127 433⁄16 1097 333⁄4 857 1911⁄16 500 131⁄16 332 141⁄2 368
8 200 431⁄2 1105 121⁄4 311 61⁄2 165 511⁄16 1297 405⁄8 1032 235⁄16 592 1511⁄16 399 183⁄16 462
H I J P 757DCDABFG 757NDCDA BFG
H
G
J
I
P
70 32 78 35
68 31 81 37
75 34 98 44
131 59 171 78
275 125 351 159
Noryl® is a registered trademark of SABIC Innovative Plastics Holding BV.
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