When I flush the toilets in my house there is a loud knocking noise coming from the water line. I have bled the air out several times, and I adjust the in-line water regulator both directions(more pressure, less pressure). This works for about a day, and then the noise comes back. Bad regulator?

To you have water hammer when you shut off a faucet? Back to you, Tom

No, just flushing the toilets. But when it hammers and I turn on a faucet, it speeds up the hammering.

When I bled the air out I went to the street, turned off the water to the house, opened all the faucets, then turned the water back on and went around the house and shut of the faucets. Tha should have eliminated the air in the pipes, right?

Sounds like you have something else going on....toilet fill valve, loose washer in stop valve symptons....if you were to shut the water off to each fixture and then turn them on one at a time and run some water, flush, you would probably find the offending culprit.

Describe the noise. Is it a loud hammer, a rattle or a machine gun sound? That's you, Tom off