We have an A.O. Smith Aqua-Aid Model V60 Water pump and storage tank. The pressure fluctuates between 35 and 58 psi when water is running. I believe this to be normal. My issue is after a period of non-use and water is run the tank will make a "bang/clunk" sound when the pump turns on. It doesn't do it ever time and we notice it more in the morning, but it does occur throughout the day. I know the noise does not come from pipes, it seems to be localized at the tank. My question is, what is causing the banging/clunking noise and how can I correct it?