Leaking Faucet Puzzle

This evening for a couple of hours my house had a major drop in water pressure while the water department fixed a pipe down the block.
Strangely, a bathroom faucet on the first floor started leaking hot water -- a slow stream, more than a drip but not a ton of water. The kitchen faucet did not leak, nor did any other fixtures in the basement or on the second and third floor.
I assumed this was just a coincidence and the cheap no-name fixture the previous owners had installed had just died at the same time, but nope. As soon as the guys finished work on the pipe and water pressure came back up, the leak stopped too.
Any idea why less water pressure caused a faucet to leak?
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You don't say what type of faucet, so I'm going to assume it was NOT one of the older faucet-washer type.
If it is one of the delta or other one-handle type, I might guess that it takes a certain amount of pressure to press the valve ball up against the seals. I sure don't like that idea though. Anyone else.
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On Dec 3, 8:50�pm, snipped-for-privacy@cox.net wrote:

a friends home has fire hydrant in front yard. each year at flushing time their T&P valve on the hot water tank opens. you probably didnt notice occasional high pressures during repairs
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