When turning the water on in the main bathroom the pressure is fine fine but when you open it up all the way the pressure goes down considerably. We do not have problems with pressure anywhere else in the house only this faucet. What could the problem be? I wouldn't worry about it but the point where the pressure starts to slow is about the spot where the hot water starts at.

Single handle, double handle?
Is it both the hot and cold slowing down?
About how old is it?
Has any plumbing work in the house been done just before this started happing?
Have you removed the shower head to see if it made any differance?

It's a single handle and it pretty old. I think at least 10 to 15 years old. Yes that tub had been worked on within the last couple of years by a plumber. I can't remember if it was happening before that or not. It is only the hot water that slows down. Should I try replacing the handle?

This message has been edited. Last edited by: msmith162,

The reason I asked about if the plumbing been worked on is often time if let's say you had a water heater replaced it will knock trash loose in the lines that shows up in the faucets at some point.
"Remove the handle" well sort of. It's really the whole stem that need to come out to be inspected and clean or better yet just replaced.
The water supply gets shut off, Relieve the pressure in the line by opening up the faucet. Remove the handle.
Remove the ring that keeps water from getting in behind the wall.
Remove the whole stem.
Once the stems out have someone turn the water on just long enough to flush the line and to see if it's getting proper flow.
If you take the whole stem to a real plumbing supply, Lowes or Home Depot they should be able to match it up so the whole thing can be replaced.
Yours is so old I feel it would be best to replace instead of just rebuild.
It's not the end of the world if you just end up with new O rings and washer.
There's dozens of differant styles of stem assembleys so it's hard to give exact instrutions or tools needed until you get it opened up.
Some can be removed with just a wrench, some need a special tool sold in any hardware store to remove it.
Just looks like a long hollow socket with a handle on it.

it also helps to know the manufactor of the faucet so try to see if there is a name on the unit write it down and take it with you to the store with the parts.