I finally replaced my 30-year-old water heater last Monday, with a 6-
year version from BOB (big orange box). Did it all myself, for less
than $400. Would've cost $600+ to have done.

Anyway, I had an issue before with a signifigant drop-off in water
pressure any time I went all-hot anywhere in the house. I still do.

The 3/4" connection pipes on top of the old WH were pretty crudded up,
and I thought that was my problem until I tried all-hot with the new
heater in place.

The copper pipes immediately before and after the WH are clean as a
whistle.

Not so much of a problem now that I don't need to go all-hot to get
anything but a stone-cold shower, but still bugs me.