Watts LF757NDCDA User Manual
For Non-Health Hazard Applications
ES-LF757DCDA/LF757NDCDA
Job Name
Job Location
Engineer
Approval
LEAD FREE
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*
Series LF757DCDA,
LF757NDCDA
Double Check Detector Assemblies
Sizes: 21/2" – 10"
Series LF757DCDA, LF757NDCDA 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 LF757DCDA, LF757NDCDA
may be installed under continuous pressure service and may
be subjected to backpressure and backsiphonage. Series
LF757DCDA, LF757NDCDA 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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LF757DCDAOSY
Features
• Lead Free* construction
• Extremely compact design
• 70% lighter than traditional designs
• 304 (Schedule 40) stainless steel housing & sleeve
• Groove fittings allow integral pipeline adjustment
• Unique 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 Lead Free* 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
Series LF757DCDA, LF757NDCDA.
LF757DCDABFG
LF757NDCDAOSY
*The wetted surface of this product contacted by consumable
water contains less than 0.25% of lead by weight.
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
Dimensions — Weight
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: Lead Free* 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
1048 B64.5
C (open)
D
A
H
G
(BFG & OSY only)
J
I
P
LF757DCDA , LF757NDCDA
SIZE DIMENSIONS WEIGHT
in. in. mm in. mm in. mm in. mm in. mm in. mm in. mm in. mm lbs. kgs. lbs. kgs.
21⁄2 301⁄2 775 163⁄8 416 31⁄2 89 291⁄16 738 211⁄2 546 151⁄2 393 813⁄16 223 133⁄16 335 139 63 147 67
3 31
4 33
6 44 1118 30
8 50 1270 37
10 56
A C (OSY) D G H I J P LF757DCDA LF757NDCDA
3
⁄8 797 187⁄8 479 311⁄16 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
⁄2 1435 453⁄4 1162 83⁄16 208 66 1676 50 1270 321⁄2 826 175⁄16 440 24 610 795 361 965 438
1
⁄8 765 51⁄2 140 443⁄4 1137 333⁄4 857 233⁄16 589 131⁄16 332 19 483 309 140 350 159
3
⁄4 959 611⁄16 170 541⁄8 1375 405⁄8 1032 277⁄16 697 1511⁄16 399 213⁄16 538 494 224 569 258
C
D
A
LF757DCDABFG , LF757NDCDABFG
SIZE DIMENSIONS WEIGHT
in. in. mm in. mm in. mm in. mm in. mm in. mm in. mm in. mm lbs. kgs. lbs. kgs.
1
⁄2 271⁄2 698 8 203 31⁄2 89 297⁄8 759 211⁄2 546 1415⁄16 379 813⁄16 223 13 330 70 32 78 35
2
3 28 711 8
4 28
6 37 940 10 254 5 127 43
8 43
A C D G H I J P LF757DCDABFG LF757NDCDA BFG
5
3
⁄4 730 815⁄16 227 311⁄16 94 3115⁄16 811 231⁄2 597 161⁄4 412 915⁄16 252 14 356 75 34 98 44
1
⁄2 1105 121⁄4 311 61⁄2 165 511⁄16 1297 405⁄8 1032 235⁄16 592 1511⁄16 399 183⁄16 462 275 125 351 159
⁄16 211 311⁄16 94 3011⁄16 779 221⁄4 565 157⁄16 392 93⁄16 233 131⁄2 343 68 31 81 37
3
⁄16 1097 333⁄4 857 1911⁄16 500 131⁄16 332 141⁄2 368 131 59 171 78
H
G
J
I
P
Noryl® is a registered trademark of General Electric Company.
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