My apartment has low pressure, especially in the shower. It's a loft building in NYC and my unit was renovated in 1985. Others in the building claim to have no issues with pressure.

I'm re-doing one bath and the walls have been removed. While the pipes running to the shower area are large, the copper piping running directly into the handle and then from the handle to the showerhead is 5/8" which looks thin. Could this be the reason my pressure is poor? I know all about the flow restrictors in showerheads but even with the head removed the water flow is very low. Would replacing these pipes with thicker ones help? What is the standard in pipe diamter?

Thanks,
Scott

Don't worry the copper going to your shower mixing valve is of standard size (1/2"). Maybe the galvanized plumbing in your apartment is so badly corroded that it has constricted the flow?
Also what time are you trying to take a shower? Is it at a peak time when others in the building are showering/bathing as well? It could be a design flaw in the plumbing system leaving you last on the water supply lines in the building and with the short end of the stick.