Our hallway bathroom sink has a problem with water pressure in the hot water line. We thought it was a bad valve, that wouldn't turn on right. SO I bought the valve, turned off the water to the house, took off the old valve (with many an exclamation and contortion to get to it under the sink), found out I bought the wrong replacement valve, went and got the right replacement valve, vcame home and put it on (with an equal number of contortions and twisting of my body under the sink into positions that a body my shape does not wish to be twisted into)--still no water pressure.
We called my father-in-law, who is a plumber (among other things), he thinks we may have a flattened pipe, or something blocking the pipe. He says it could be anywhere in the line. Terrific.
We'll deal with the low water pressure.
Take care. Stick.