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Smith-Blair Joint Restraint
Smith-Blair Style 471 PipeLock Restraint Coupling - Ductile, 3-48 in
Smith Blair
Smith-Blair Style 471 PipeLock Restraint Coupling - Ductile, 3-48 in
- Price
- From $413.55
Smith-Blair Style 920 Flange-Lock Restrained Flanged Coupling Adapter - PVC, 3-36 in
Smith Blair
Smith-Blair Style 920 Flange-Lock Restrained Flanged Coupling Adapter - PVC, 3-36 in
- Price
- From $402.20
Smith-Blair Style 923 Flange-Lock Restrained FCA Sleeve - MJ x Flange, 3-48 in
Smith Blair
Smith-Blair Style 923 Flange-Lock Restrained FCA Sleeve - MJ x Flange, 3-48 in
- Price
- From $298.20
Smith-Blair Style 472 PipeLock Restraint Coupling - PVC, 3-36 in
Smith Blair
Smith-Blair Style 472 PipeLock Restraint Coupling - PVC, 3-36 in
- Price
- From $411
Smith-Blair Style 911 Flange-Lock Restrained Flanged Coupling Adapter - Ductile Iron and Steel, 3-48 in
Smith Blair
Smith-Blair Style 911 Flange-Lock Restrained Flanged Coupling Adapter - Ductile Iron and Steel, 3-48 in
- Price
- From $392.11
Smith-Blair EZW Seal & Restraint Line Cap - 2-12 in
Smith Blair
Smith-Blair EZW Seal & Restraint Line Cap - 2-12 in
- Price
- From $227.44
Smith-Blair EZW Maxi-Grip Restraint Reducing Coupling - 3-12 in
Smith Blair
Smith-Blair EZW Maxi-Grip Restraint Reducing Coupling - 3-12 in
- Price
- From $482.02
Smith-Blair EZW Restrained Flanged Coupling Adapter - 2-12 in
Smith Blair
Smith-Blair EZW Restrained Flanged Coupling Adapter - 2-12 in
- Price
- From $381.58
Smith-Blair EZW Maxi-Grip Restraint Coupling - Straight, 2-12 in
Smith Blair
Smith-Blair EZW Maxi-Grip Restraint Coupling - Straight, 2-12 in
- Price
- From $303.65
Smith-Blair Style 907 Restraint Plate - Carbon Steel, 3-Hole, 4-48 in
Smith Blair
Smith-Blair Style 907 Restraint Plate - Carbon Steel, 3-Hole, 4-48 in
- Price
- From $93.80
Smith-Blair Style 101 Tie Rod & Nut Set - Alloy Steel, 5/8-1-1/2 in
Smith Blair
Smith-Blair Style 101 Tie Rod & Nut Set - Alloy Steel, 5/8-1-1/2 in
- Price
- From $32.36
Smith-Blair Style 473 PipeLock Restraint Steel Coupling - 3-36 in
Smith Blair
Smith-Blair Style 473 PipeLock Restraint Steel Coupling - 3-36 in
- Price
- From $396.89
Smith-Blair Joint Restraint
Smith-Blair · Joint Restraint · Thrust Restraint · 2 in to 48 in
Smith-Blair Joint Restraint: Hold the Pipe Without Thrust Blocks
Every bend, tee, reducer and dead end on a pressurized main pushes on its joints with thousands of pounds of force. Smith-Blair restraint products carry that thrust in the fitting itself: PipeLock and EZW restrained couplings, Flange-Lock and EZW-F restrained flange adapters, the EZW-C restrained line cap, and 907 lugs with 101 tie rods for flanged piping.
14 ProductsEvery restraint method
2–48 inPipe sizes
To 350 PSIRestrained rating
DI · PVC · Steel · PEMatched grip
No Cure TimeRestrain and backfill
Water under pressure pushes on every surface that changes its direction or its area. On a straight run those forces cancel. At a bend, tee, reducer, valve or dead end they do not, and the leftover force tries to slide the pipe out of its joint. Push-on and mechanical joints, standard couplings and standard flange adapters seal against that force but do not hold against it.
This collection is everything Smith-Blair makes to hold it. Send the pipe material, OD, working and test pressure and the fitting you need to restrain, and we confirm the product and part number the same day: call 1-888.510.4036 or email sales@watermainsupply.com. Genuine Smith-Blair equipment, factory-new in original packaging — sold and supported by Watermain Supply, an independent industrial supplier.
How Much Thrust Is on the Joint?
Worked for an 8 in ductile iron main (9.05 in OD, 64.3 sq in) at 150 PSI. Thrust rises in step with pressure and with the square of the OD.
| Fitting | Formula | Thrust, 8 in at 150 PSI |
|---|---|---|
| Dead end, cap or closed valve | P x A | 9,649 lb |
| Tee, on the branch | P x A of the branch | 9,649 lb |
| 90° bend | 2 x P x A x sin 45° | 13,646 lb |
| 45° bend | 2 x P x A x sin 22.5° | 7,385 lb |
| 22-1/2° bend | 2 x P x A x sin 11.25° | 3,765 lb |
| 11-1/4° bend | 2 x P x A x sin 5.625° | 1,892 lb |
| 8 x 6 in reducer | P x (A large - A small) | 4,040 lb |
Design for test pressure: hydrostatic tests usually run 1.5 times working pressure or more, and surge adds to it. Size every restraint for the highest pressure the line will see, not the normal operating pressure.
Three Ways to Restrain a Joint
Every restrained water main uses one or more of these. The job conditions decide which.
| Concrete thrust block | Tie-rod harness | Restrained fitting | |
|---|---|---|---|
| How it holds | Concrete bears on undisturbed soil | Rods in tension tie flange to flange | Wedges or grip ring bite the pipe |
| Install time | Forms, pour, cure before pressure | Hours, inspectable | Minutes; backfill the same day |
| Direction | One way | Both ways | Both ways |
| Soil dependence | Total: poor or disturbed soil fails it | None | Low: pipe friction does the rest |
| Future digging nearby | Can undermine the block | Not affected | Not affected |
| Space needed | Large, behind the fitting | Around the flanges | The fitting only |
| Smith-Blair products | — | 907 Plates, 101 Tie Rods | PipeLock, EZW, Flange-Lock, RazorLock |
How Smith-Blair Restraints Grip the Pipe
Four mechanisms, each matched to a pipe material and a job.
Cam-Lock Wedges
Individual single-tooth ductile iron wedges in the follower gland bite the pipe while a standard MJ gasket seals. Black wedges for ductile iron and steel, red wedges for PVC. Used in PipeLock 471, 472, 473 and Flange-Lock 911, 920.
EZ-W Grip Ring
A case-hardened grip ring behind an SBR timing gasket: the gasket seals first, then the ring sets as the bolts are drawn up. Stab fit, no disassembly. Used in the EZW couplings, EZW-C line cap and EZW-F adapter.
RazorLock Dual Drive
One bolt per end compresses gasket and grip together through a controlled-flex follower, on a wide-range body that fits any mix of steel, iron, PVC, PVCO and PE. Used in the 431.
Tie-Rod Harness
907 triangular lugs on each flange and 101 alloy tie rods between them carry the thrust in tension around a standard flanged connection. Rod count set by flange size and pressure.
Restraint by Location in the Line
What needs holding decides the product.
| Where | Restrain with |
|---|---|
| Pipe-to-pipe joint or repair | PipeLock 471 DI, PipeLock 472 PVC, PipeLock 473 PVC to DI or steel, EZW Straight, RazorLock 431 |
| Change of pipe size | EZW Reducing: restrains the reducer thrust in the fitting itself |
| Flanged valve, meter or pump | Flange-Lock 911 DI and steel, Flange-Lock 920 PVC, Flange-Lock 923 body with Cam-Lock gland, EZW-F |
| Dead end or test closure | EZW-C Line Cap: seals and grips the pipe end |
| Flange-to-flange piping | 907 Plates lugs with 101 Tie Rods: the tie-rod harness |
| Long repair span, MJ ends | PipeLock 477 sleeve with MJ gaskets and restraints, 3–48 in |
Standard couplings, flange adapters and end caps are in Couplings, Flanged Coupling Adapters and End Caps.
Restraint by Pipe Material
Gripping steel, ductile iron, PVC and polyethylene are different problems. Use the restraint made for the pipe.
| Pipe | Restraint products | Key rule |
|---|---|---|
| Ductile iron | PipeLock 471 (3–48 in), Flange-Lock 911, EZW Straight, EZW-F, RazorLock 431 | Black Cam-Lock wedges |
| Steel (IPS) | EZW Straight, EZW Reducing, EZW-F, RazorLock 431; PipeLock 471, PipeLock 473 and Flange-Lock 911 at 3–12 in | Black Cam-Lock wedges |
| PVC (C900, C905, IPS) | PipeLock 472, PipeLock 473, Flange-Lock 920, EZW Straight DR26+, RazorLock 431 | Red Cam-Lock wedges, SDR 26 or heavier |
| HDPE and PE | EZW Straight, EZW Reducing, EZW-F, RazorLock 431 | Stiffener in the pipe end, always |
| Cast iron | RazorLock 431 | Other styles: confirm with us first |
| Flanged piping | 907 Plates and 101 Tie Rods | Any bolted flange, 4–48 in |
PVC and PE are the pipes that most need restraint: a push-on PVC joint carries no thrust on its own, and PE relaxes under load. On PVC, use red-wedge or PVC-rated restraints on SDR 26 or heavier wall; on PE, always fit a stiffener.
Tie Rods per Flanged Joint: 907 Lugs and 101 Rods
Smith-Blair recommended tie-rod quantity by flange size and maximum line pressure.
| Flange | 50 PSI | 100 PSI | 150 PSI | 200 PSI | 250 PSI | Rod size |
|---|---|---|---|---|---|---|
| 4 in | 2 | 2 | 2 | 2 | 2 | 5/8 in |
| 6 in | 2 | 2 | 2 | 2 | 2 | 5/8 in |
| 8 in | 2 | 2 | 2 | 2 | 2 | 5/8 in |
| 10 in | 2 | 2 | 2 | 3 | 3 | 5/8 in |
| 12 in | 2 | 2 | 3 | 3 | 4 | 5/8 in |
| 14 in | 2 | 2 | 3 | 3 | 4 | 3/4 in |
| 16 in | 2 | 2 | 2 | 2 | 3 | 1 in |
| 18 in | 2 | 2 | 2 | 3 | 4 | 1 in |
| 20 in | 2 | 2 | 3 | 3 | 4 | 1 in |
| 24 in | 2 | 2 | 2 | 3 | 4 | 1-1/4 in |
| 30 in | 2 | 2 | 3 | 4 | 6 | 1-1/4 in |
| 36 in | 2 | 3 | 5 | 6 | 8 | 1-1/4 in |
| 42 in | 2 | 4 | 6 | 8 | 10 | 1-1/4 in |
| 48 in | 2 | 4 | 6 | 8 | 9 | 1-1/2 in |
Restrained Length: Restrain More Than the Fitting
Restraining only the bend is a common mistake.
What It Is
- The length of pipe each side of a fitting whose joints must all be restrained.
- Soil friction on that length holds the thrust the fitting creates.
- Calculated by the design engineer from pressure, size, cover, soil and fitting type.
What It Means on the Job
- Every joint inside the restrained length needs a restrained coupling or gland.
- Repairs inside a restrained zone must be restrained too: use a PipeLock or EZW, not a standard coupling.
- Larger pipe, higher pressure and shallow cover all lengthen the zone.
All Restraint Products
Smith-Blair datasheet figures. Working pressure also depends on the pipe, its class and the installation.
| Product | Type | Pipe | Sizes | Pressure | Restraint |
|---|---|---|---|---|---|
| PipeLock 471 | Coupling | DI to DI | 3–48 in | 350 PSI | Cam-Lock wedges |
| PipeLock 472 | Coupling | PVC to PVC | 3–36 in | 235 PSI | Cam-Lock wedges |
| PipeLock 473 | Coupling | PVC to DI or steel | 3–36 in | 235 PSI | Cam-Lock wedges |
| PipeLock 477 | Sleeve | DI, PVC; steel 3–12 in | 3–48 in | 350 PSI sleeve | Takes MJ restraints |
| EZW Straight | Coupling | Steel, DI, PVC, PE | 2–12 in | 300 PSI | Grip ring, timing gasket |
| EZW Reducing | Reducing coupling | Steel, DI, PVC, PE | 3–12 in | 300 PSI | Grip ring, timing gasket |
| RazorLock 431 | Coupling | Any mix incl. PE | 4–8 in | 250 PSI | Dual Drive grip |
| EZW-C Line Cap | Line cap | IPS and DIPS OD | 2–12 in | By pipe type | Grip ring |
| EZW-F | Flange adapter | Steel, DI, PVC, PE | 2–12 in | 175 PSI | Gripping band |
| Flange-Lock 911 | Flange adapter | DI; steel 3–12 in | 3–48 in | 150 PSI | Cam-Lock, black |
| Flange-Lock 920 | Flange adapter | PVC | 3–36 in | 175 PSI | Cam-Lock, red |
| Flange-Lock 923 | Flange adapter body | With 111 or 120 gland | 3–48 in | 150 PSI | Gland sets the pipe |
| 907 Plates | Restraint lug | Bolted flanges | 4–48 in | 50–250 PSI | Tie-rod harness |
| 101 Tie Rods | Tie rod set | With 907 lugs | 5/8–1-1/2 in rods | By rod count | Tension member |
PipeLock 471
DI coupling, 3–48 inView
PipeLock 472
PVC coupling, 3–36 inView
PipeLock 473
PVC to DI or steelView
PipeLock 477
Restraint sleeve, 3–48 inView
EZW Straight
Grip ring coupling, 2–12 inView
EZW Reducing
Restrained reducer, 3–12 inView
RazorLock 431
Any pipe, 4–8 inView
EZW-C Line Cap
Restrained dead endView
EZW-F
Restrained FCA, 2–12 inView
Flange-Lock 911
Restrained FCA, DI and steelView
Flange-Lock 920
Restrained FCA, PVCView
Flange-Lock 923
FCA body for Cam-LockView
907 Plates
Restraint lugs, 4–48 inView
101 Tie Rods
Tie rods and nutsViewJoint Restraint Questions
What is joint restraint?
Any method that stops line pressure from pushing pipe out of its joints: a concrete thrust block, a tie-rod harness, or a fitting that grips the pipe itself. A standard coupling or flange adapter seals but does not restrain.
Where does a water main need restraint?
Wherever flow changes direction or the line ends: bends, tees, reducers, dead ends, caps, plugs and closed valves, plus the joints on either side of them out to the restrained length your engineer calculates.
How do I calculate thrust?
Dead end or tee branch: pressure times the pipe area. Bend: 2 times pressure times area times the sine of half the bend angle. Reducer: pressure times the difference in areas. Use the test pressure if it is higher than working pressure.
What is restrained length?
The length of pipe on each side of a fitting that must be restrained so soil friction and bearing can hold the thrust. It depends on pressure, pipe size, depth of cover, soil and the fitting, and is calculated by the design engineer, for example with the DIPRA or Uni-Bell methods.
Thrust block or restrained joint?
Thrust blocks need undisturbed soil, formwork and cure time, and can be undermined by later digging. Restrained joints install in minutes, work in poor soil and tight right-of-way, and hold in both directions. Many utilities now specify restrained joints by default.
Why are there black and red Cam-Lock wedges?
Black wedges are for ductile iron and steel; red wedges are made for PVC so they grip without overstressing the wall. Use the Flange-Lock 911 or Cam-Lock 111 on metal pipe and the 920 or Cam-Lock 120 on PVC.
Can I restrain PVC pipe?
Yes, with PVC-specific restraints: the PipeLock 472 and 473, the Flange-Lock 920, the EZW couplings on DR26 or heavier, and the RazorLock 431. Smith-Blair limits PVC restraint to SDR 26 or heavier wall.
Can I restrain HDPE pipe?
Yes, with the EZW couplings, EZW-F and RazorLock 431, always with a stiffener in the pipe end. The stiffener carries the grip load the polyethylene wall cannot.
How many tie rods does a flanged joint need?
It depends on flange size and pressure. With Smith-Blair 907 lugs and 101 rods, 4 to 8 in flanges need 2 rods up to 250 PSI, while a 42 in flange needs 10 at 250 PSI. The full table is on this page.
Does a restrained coupling allow deflection?
Some do. PipeLock and Flange-Lock allow up to 5° depending on size, and the RazorLock 2° per end. Check each listing before using deflection to make a bend.
Are restraint products returnable?
No. Smith-Blair restraints are made to order and non-returnable, so we confirm the pipe material, OD and pressure before the order ships.
Skip the Concrete. Restrain the Joint.
Send the pipe material and OD, the working and test pressure, and what you need to restrain: joint, reducer, valve, dead end or flanged connection. We reply the same day with the product, part number, price and ship date.
Technical data on this page is taken from Smith-Blair product literature and is subject to change by the manufacturer. Thrust figures are examples; restraint design and restrained length are the responsibility of the project engineer. All Smith-Blair products are made to order and non-returnable.
Xylem, Smith-Blair, PipeLock, Cam-Lock, Flange-Lock, EZ-W, Maxi-Grip, RazorLock and Flexi-Coat are trademarks of Xylem Inc. or its subsidiaries, used here for product identification only.
Watermain Supply is a DBA of E4 Industrial LLC, an independent industrial supplier based in Houston, Texas.
Xylem, Smith-Blair, PipeLock, Cam-Lock, Flange-Lock, EZ-W, Maxi-Grip, RazorLock and Flexi-Coat are trademarks of Xylem Inc. or its subsidiaries, used here for product identification only.
Watermain Supply is a DBA of E4 Industrial LLC, an independent industrial supplier based in Houston, Texas.
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