Within the last week, my pipes have started to bang and vibrate (water hammer?) I shut off the main valve and opened the highest and lowest faucets to drain the water, then turned the water back on with hopes of flushing out the air. I also bought a water pressure gauge and my pressure at the lowest faucet is 50-60. The banging and loud vibration intermittently continues when either flushing the toilets, or sometimes turning on the shower or the bathroom sink faucet. I'm at a loss to know what to do since the pressure seems normal from the gauge and I've tried draining the air out already. I notice the noise occurs most and is loudest when water hasn't run for hours. After I hear the hammer noise, if I turn on water within a few minutes, there is no noise. Any clues?