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Installation
Deflection
Gasketed joints permit an angular deflection of 2° at the joint.
Adequate deflection can usually be achieved for gentle curves by
using the inherent flexibility of the pipe itself, without using joint
deflection.
Thrust Blocking Gasket Joints
All gasket-joint piping requires adequate thrust restraints to prevent
movement from forces generated by changes in direction, valve
operation, dead ends, reduction in pipe size, and other areas where
thrusts can be developed. The size and type of thrust restraint
depends on the pipe size, type of fitting, soil properties, and waterhammer
possibilities. Keeping flow velocities at or below 5 ft/sec
will help minimize surge pressures. Fittings and valves used to
make vertical changes in direction should be anchored to the thrust
restraint to prevent outward and upward thrusts at the fitting junctures.
In pressure lines, valves 3" in diameter and larger should be
anchored to the thrust restraint to prevent movement when operated.
Consideration should also be given for the proper support, anchoring,
and thrust restraint for lines installed on slopes.
The size of thrust block required (in square feet) can be determined
by dividing the total thrust developed (in psi) by the capacity of the
soil (in pounds/square foot).
The most common method of thrust blocking involves the pouring
of concrete (to the size of block required) between the pipe fitting
and the bearing wall of the trench. Mechanical thrust restraint with
PVC pipe.
Thrust Blocks
Thru Line connection, tee
Direction change, elbow
Thrust Retainers
Thru Line connection,
cross used as tee
Direction change, elbow
Thrust in lb. @ 100 psi Operating Pressure
Pipe
Size (in.)
90°
Bend
45°
Bend
22.5°
Bend
Tee, Cap Plug,
60° Bend
2 645 350 180 455
2-1/2 935 510 260 660
3 1,395 755 385 985
4 2,295 1,245 635 1,620
6 4,950 2.680 1,370 3,500
8 8,375 4,540 2,320 5,930
10 13,040 7,060 3,600 9,230
12 18,340 10,000 5,240 13,000
14 21,780 11,770 6,010 15,400
16 28,440 15,370 7,850 20,110
18 35,990 19,450 9,930 25,450
20 44,430 24,010 12,260 31,420
24 63,970 34,570 17,650 45,240
Safe Bearing Capacity
Soil
Capacity (lb./sq. ft.)
Muck, peat, etc. 0
Soft clay 1,000
Sand 2,000
Sand and gravel 3,000
Sand and gravel cemented with clay 4,000
Hard shale 10,000
Change line size, reducer
Direction change,
tee used as elbow
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