The water suddenly stopped coming out of the shower head. It is only a shower head with a separate hot handle and a separate cold handle. I turned off the shower and then back on and the water came on. I had a plumber come out and check it two months ago. He found sediment in the shower head, cleaned it out, and since then it was fine. Should the hot/cold stems be replaced as he now recommends? I bought a new shower head today, in case that is the problem. He said it could be the valve which would involve cutting into the drywall behind the shower at a cost of $800-$1,000. Any help or advice is greatly appreciated!