I have a low flush toilet by armitage shanks fitted four years ago in my disabled shower room. When I flush the cistern there is a loud noise when I depress THE HANDLE . The water from the mains comes into the valve body and exits from the body at the top through a small angled plastic tube down to the bottom of the cistern
Hi I have the same problem & I know how very irritating it is, I'm afraid I don't have the cure for it yet. Except I'm pretty sure it's an air lock. I'm searching for a way to bleed the the cold water system to get rid of it. Sorry I can't give you an answer yet, but if I do I'll send you another message.