Its an older house built in 1958. Is a 100 psi ok for glavanized?
100 is high for anything. 60 to 80 is optimal, IMO.
They probably cranked the regulator to get more water , dint happen to check flow did you
40 to 80 is called for in the IRC.
Knowing the water in that area and the age of the home I would bet they could barely get a pencil lead through a 1/2" galvanized pipe by this time. I think Wayne is right… they probably raised the pressure to get some sort of flow.
Me thinks its time to replace.
I agree with Wayne and Stephen , galvanize sucks at that age