When using the washer and sometimes when turning on th ewater faucet I hear a bang. When I check the boiler room I notice water also driping from the hot water relief valve is this drip caused by the water hammer.

I don't think so. Relieve valve will drip if your house water pressure is too high - usually over 150psi - or water inside water heater is reaching 200 F.

I would check house pressure first. Screw pressure gauge on any water outlet past regulator and see how much pressure you have. You should have reading anywhere between 15 psi and 75 psi.

Chances are your pressure regulator is not working properly and needs to be replaced. While on it, replace pressure relieve valve too. Once dripping, it may not hold the same pressure again.

Back to you. Milo