pipes under house sound like a machine gun

[cbelt3]

yep- water drain is the main solution.
Shut off your main water valve
Find the LOWEST tap in your house
Open it
Now go up your house and open ALL the taps (even flush the johns, hot water too, open the outside taps, etc.

Now go back down and turn on your water supply. Then go back up and close taps from the bottom up.

Once you're done, no more water hammer.