On Fri, 14 Apr 2017 15:14:12 -0000 (UTC), HerHusband
wrote:

She has hot water everywhere but the bathroom sink.
The pipes are behind a beautiful tile wall. It's at least 6 feet from
the bathtub to the sink**. The valve under the sink turns easily,
quite a bit from off to on and I'm sure it's all the way on. I guess
I'll turn it on and off a few more times, but .... Is there any point
to taking the valve apart on the hope that the blockage can be pried
to pieces with an awl or something?

Turn off the water to the house, then disconnect the sinks hot water hose
from the shut-off valve under the sink. Look inside the shutoff valve as
you open and close it (use a mirror and flashlight if you need to). You
should be able to see the valve opening and closing inside. If not, the
shut off valve is probably broke and will need to be replaced.

If the valve appears to be working, connect a hose to the valve and place
it in a container. You can use the hose that runs to the sink if you can
access it. Then turn the water on and open the valve. If water comes out
you know the clog is in the sink faucet. If water does not come out there
is a blockage somewhere in the water line before the shutoff valve.

The faucet itself is one-piece, one handle, and when all the way to
hot, almost nothing comes out, and it's not hot.

If you determine the faucet is broken, it should be fairly simple and
inexpensive to install new washers, seals, or cartridges.

hot water pressure at the tub is much lower than the cold water pressure.

Do you know what kind of plumbing you have? If it's old galvanized pipe, it
may have corrosion build up inside restricting water flow. If that's the
case, the only option is to cut out the pipe and replace it.

I don't understand the one-handle shower valves

Most single handle shower valves have pressure balancing valves in them.
This allows the valve to balance the hot and cold water so you don't get
scalded if someone flushes the toilet or something.

Pressure balancing valves can stick, which would typically give you only
hot or cold water when you turn on the shower.

Anthony Watson
www.watsondiy.com
www.mountainsoftware.com
In North America for the last 10 years or so pressure balancing
faucetes have become popular, but the lower priced stuff still doesn't
have PB valves (and none in my house do). I rather doubt the house in
question has high end fixtures.

Also, since both the tub and sink have low pressure, and given the age
of the place. I'd put better than even money it's got some old
galvanized pipe - and the hot lines plug up before the cold generallt
speaking.