Hot Water flow diminishes on startup, why?

Dear Experts,
I'm visting my parent's house. The plumbing in their bathtub is really odd.
You turn on the hot water. You get a certain flow and heat. As usual, I then add the cold water so it's not too hot.
Then, the hot water flow starts to diminish. The water gets colder.
When I turn off the cold water completely, I see just a trickle of hot water! So, I will open it up some more.
After I then open up the cold water, the same thing will happen!!!
Finally, after two iterations, I have to open the faucet almost full to get a consistent flow.
This takes a minute or two to adjust when you are trying to take a shower.
They have two faucets. One for hot, and one for cold.
What is the cause and the solution? Change the valve?
Thanks a lot!
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On Mon, 25 Jun 2007 08:05:24 -0700, condor snipped-for-privacy@yahoo.com wrote:

    WTF is this in alt.hvac ? Call a fucking plumber.
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I don't know if it's too much caffeine, ethanol, drugs or what--but I'd suggest you refrain from posting in this condition. Chill, please! Not everybody is as "smart" as you. *Not* posting a reply to a message you find silly is oftentimes better than all other options. 'Nuff said--I'm out of this thread for good.
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