My servis washer is about 18 months old and on the last wash it began crackling like a bunch of popcorn popping on its spin cycle. By the time I'd located the noise the spin was winding down and I put it to the back of my mind. Now I've gone to do a wash and as the washer starts it does a draining bit before it adds water and the noise sounds like the popcorn again or like broken glass dragging on metal. What do you think could be wrong. I have no plumbing experience so please simplify. Thanks very much.