Why is it that some municipalities demand both joint restraint and thrust blocking? I guess thrust blocks can be altered or removed during subsequent work on other utilities. So backing up thrust blocks with restraints could make sense. But why should restrained joints be backed up by thrust blocks? Do they think the restraints may be removed or damaged? Or that they may corrode? Maybe they wish to guard against poor workmanship or design…
The other question is why do some contractors insist on using both even when they are not both required.
From my experience it is a lack of knowledge in why restraining the fitting, with either thrust blocks or mechanical restraints, is necessary. They feel that if one of them is good by itself, it must be even better if you use both. A big waste of money if you ask me.
Above is a snippet.