I agree with bimr. Thrust restraint in piping keeps it from separating at joints where thrust exists (eg. bends, tees, dead ends). If all connections are fusion bonded, then no separation can occur and there is no need for thrust restraint.
I imagine that there are no branches on this force main? I did a fire main in PE and had to but thrust blocks on the T's to avoid them possibly breaking off and also had to put some thrusts to prevent it lifting so if you have some vertical bends you may have to put thrusts on them.
suppose it all depends on what pressures and fluctuations you expect
