"Ken Moiarty" wrote in message
If you're handy
enough, take the valve out and see if that doesn't increase the
pressure. If it does, then just get a new valve. BTW, you shouldn't
need a balancing valve. Something is awry somewhere. Perhaps you'll
end up repiping the main arteries that feed the fixtures.

This comes to me as a surprise. In every house I've ever lived in
prior to, as well as including, this one, people have had to time their
showers (or tell others before showering) in order to avoid being
scalded or cold-shocked while showering. I remember my Dad turning
down the thermostat of a new hot water tank that had just been
installed in his house, as a safety precaution to decrease the chance
of somebody getting seriously injured while showering in the event that
somebody opened or closed a tap somewhere unawares during.

I've never lived in a house with such a problem, and I've seen some
pretty corroded galvanized pipes. It would take a significant constriction
in the cold line to make this a problem if you have reasonable supply
pressure.

You really need to be looking at your static water pressure and make sure
all valves in the supply are open fully.

Bob