Hot water line to bath tub

replying to Jscott, Iggy wrote: The low water pressure is probably due to the hard-water, it's cholesterol to pipes and taps where air enters and flow stops to clog them more and more shut over time...a full replacement of the tap and more is the only fix. However, the piping seems to have been done with an excessive amount of flux (quite acidic), which caused all of the green (light corrosion) on the outside and ultimately the white (severe corrosion).

If there's a lot of flux outside, then there's a lot inside. Due to the hard-water though, the excessive flux was coated and covered away from the water's erosion of it, resulting in rotting the pipe uninhibited. It's best to chop the piping back to where it's still solid and clear to get everything back to normal operation.