I have this bathtub that gives low flow/low pressure from the spout. It takes a long time to fill up the bath tub. I have removed the spout to see if there was any build up but not so much and all I see is a copper rod where the spout is attached to it. Is it possible to remove the copper rod or is it already soldered on? I am not sure that might be the case or it could be the pipes that have some kind of build up in the "arteries"? Or is it something have to so with the faucet handles? Not really sure what to do

I know it seems like low pressure but it is mostlikley low volume, pressure is pretty much a constant throughout a home. Your volume could be reduced by dberis in the mixing valve. Move your valve to all cold for a moment and then to all hot, were they the same?

Both are same.