Low Hot Water Pressure - new tank - dielectric

[Gregmech26]

The Rheem 75-gallon "commercial" water heater I just purchased has two GIANT dielectric unions on 3/4 copper pipe. The plumber said they were mandatory.

 

[Sylvan]

I do not know if dielectric unions are "mandatory" as many times I use a dielectric nipple as I don't trust these types of unions with rubber /plastic for integrity with expansion and contraction

The code as far as I know frowns upon electrolytic action taking place meaning galvanized and copper /brass being connected

Unions just make it easier for the next person to remove the tank