The Ontario Building Code | Thrust Restraint of Water Service Pipes
(1) pipe clamps and tie-rods, thrust blocks, locked mechanical or push-on joints, mechanical joints utilizing set screw retainer glands, or other suitable means of thrust restraint shall be provided at each change of direction of a water service pipe 4 in. or more in size and at all tees, plugs, caps and bends.
(a) between undisturbed earth and the fitting to be restrained and shall be of sufficient bearing area to provide adequate resistance to the thrust to be encountered, and
(b) so that the joints will be accessible for inspection and repair.
(3) Concrete thrust blocks shall have a minimum compressive strength of not less than 10 MPa after 28 days.
(4) Thrust blocks shall not be used to restrain vertical pipe.
7.3.5. Protection of Piping