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UNIVERSAL LOW
PRESSURE
The Universal Low Pressure (U3, UR) check valve is a one piece body machined from bar stock and is designed for
minimum pressure drop. The valve has a light-weight, compact design that provides maintenance-free, dependable
service. NPT threads are per ASME B1.20.1. Also available with ISO 7 “Rp” threads. (UR). These valves can also be used
as a low pressure relief valve or vacuum breaker by using the desired spring settings.
NOTE: Many valves in this series can be supplied with B16.34 certification. Consult the factory for more information.
A Nom.
Pipe
Size Hex q Orifice
Code A Size B C Diameter
Size
3/8 C 2.16 13/16 3/8 NPT 0.348
1/2 D 2.71 1-1/8 1/2 NPT 0.464
C (TYP)
3/4 F 2.95 1-1/4 3/4 NPT 0.593
B 1 H 3.64 1-5/8 1 NPT 0.890
1-1/4 I 3.91 2-1/4 1-1/4 NPT 1.135
1-1/2 J 4.36 2-1/2 1-1/2 NPT 1.385
2 K 5.85 3 2 NPT 1.555
2-1/2 L 5.50 3-3/4 2-1/2 NPT 1.555
3 M 6.25 4-1/2 3 NPT 2.025
FLOW 4 N 7.13 5-1/2 4 NPT 2.560
qMay be larger and/or round.
Body Material w Availability Non-Shock Pressure-Temperature Rating
316 Stainless Steel (SS)
Carbon Steel (CS) Standard
Brass (BR)
3/8” - 3”
Alloy 20 (A2) 4”
Alloy C-276 (HC) Semi-standard 3000 PSIG @ 100°F
1500 PSIG @ 100°F
(1500 PSIG for o-ring seats)
Alloy 400 or Monel ® (MO)
Alloy B (HB) Contact the factory for these or
Titanium (TI) other materials
wSee page 54 for material grade information.
2018 MADE IN USA CHECK-ALL VALVE® MFG. CO. Phone: 515-224-2301 Fax: 515-224-2326
Note: All flow curves and Cv values presume the valves
Universal Low Pressure are fully open with 1/2 PSI cracking pressure springs.
For Water at 72°F Consult the factory for more information.
100
STYLE U3
Cv VALUES & VALVE WEIGHTS
2”
1- /4”
2”
8” 2” 4” 1/ SS & CS
1/
3/ 1” 3”
1
3/ 1/ 2” 2- 4”
PRESSURE DROP - PSI
Cv
1-
SIZE BRASS
ALLOYS
1.9 3/8 3.0 oz. 3.3 oz.
4.3 1/2 8.5 oz. 9.1 oz.
10 7.2 3/4 9.6 oz. 10.1 oz.
14.6 1 1.2 lb. 1.3 lb.
28.8 1-1/4 2.9 lb. 3.2 lb.
31.9 1-1/2 3.6 lb. 3.9 lb.
42.0 2 6.5 lb. 7.2 lb.
50.0 2-1/2 9.2 lb. 10 lb.
89.0 3 14.3 lb. 15.5 lb.
140 4 21.7 lb. 23.9 lb.
1
1 10 100 1000 See page 49 for Flow Formulae.
Valve weights are approximate.
WATER FLOW RATE - GPM
HOW TO ORDER
CHECK-ALL STYLE U3
BODY MATERIAL SPRING CRACKING PRESSURES (PSI) Note: Many other cracking pressures are
ALLOY 20 = A2 Must use decimal as a character unless available. All spring tolerances +/- 15%.
BRASS = BR selecting NO SPRING. Specify Exact Setting
CARBON STEEL = CS SPRING RANGES EXAMPLE
ALLOY B = HB .000 TO .999 = .500 Note: Many other cracking pressures are
SPRING CRACKING PRESSURES
ALLOY C-276 = HC 1.00 TO 9.99 = 1.50
Replace “X” with actual desired setting. available. All spring tolerances +/- 15%.
ALLOY 400 OR MONEL® = MO 10.0 TO 85.0 = 15.0 SPECIAL OPTIONS
Must use decimal as a character.
316 SS = SS NO SPRING = NOSPRG T = FEP ENCAPSULATED SPRING
(PSI) FORMAT EXAMPLE
TITANIUM = TI STANDARD CRACKING PRESSURES q
.000 TO .999 = .XXX .500 See p. 4 for temperature rating
See p. 3 for temperature rating .125 .500 1.50 3.50
1.00 TO 9.99 = X.XX 1.50
(Sizes C-I Only) Contact the factory for more options
10.0 TO 99.9 = XX.X 15.0
NO SPRING = NOSPRG NOSPRG
U
VALVE STYLE
F 3/8
SIZE
= C
SEAT MATERIAL w
AFLAS ® = AS
SPRING MATERIAL
316 SS = SS
NPT Threads = U3
1/2 = D BUNA-N = BN ALLOY C-276 = HC
ISO 7 Rp Threads = UR
3/4 = F EPDM e = EP ALLOY B = HB
1 = H KALREZ ® = KZ ALLOY X750 OR INCONEL® X750 = IX
1-1/4 = I “METAL-TO-METAL” = MT ALLOY 400 OR MONEL® = MO
1-1/2 = J NEOPRENE = NE 17-7PH SS = PH
2 = K PTFE = TF TITANIUM = TI
2-1/2 = L VITON ® = VT See p. 4 for temperature ratings
3 = M See p. 3 for temperature ratings
4 = N
Listed above are the most common material selections. Please contact the factory for additional options.
q.500 PSI is the only standard cracking pressure for spring materials other than Stainless Steel. .125 PSI springs are
not recommended for installations with flow vertical down.
wSeat materials other than “metal-to-metal” have a maximum pressure rating of 1500 PSI. “Metal-to-Metal” and PTFE
seats are not resilient. See page 50 for allowable leakage rates.
eEP seats not recommended for use with Carbon Steel valves.
www.checkall.com sales@checkall.com ISO 9001 CERTIFIED MADE IN USA 2018
Trademarks Used
AFLAS® AGC Chemicals Americas, Inc. INCONEL® Special Metals Family of Companies KALREZ® E.I. du Pont de Nemours and Company
MONEL® Special Metals Family of Companies VITON® E.I. du Pont de Nemours and Company
