Occassionally when running my hot water, the central heating pipes make a noisy sound, the pipes start howling, I believe this is trapped air so what I've recently done is I've turned the stop tap off which stops all the water from entering house. I then completly ran out the hot water after which I then open all the water taps so when turning back on the stop tap all trapped air would be pushed out and solving my problem. The noise has got worse and my pipes are now vibrating.... Any Hints???
This sounds like water hammer, a very common problem caused by the closing of valves or taps which create water shockwaves that make loose copper mains water pipes move and vibrate. Clip or secure loose copper mains water pipes or change some of it for plastic pipe or fit a water shock absorber in the main water pipe. It's not air.