So, my shower stopped working. Thought it might be maximum calcium build-up, and I do have that problem. But, read a thread here about the 'Vacuum Breaker' on the shower outlet; thought I would give it a try. Not only was it the reason the shower stopped working, but after replacing, the water flow to the shower is substantially greater! What a pleasure! Amazon: Delta faucet, U4900-PK- Vacuum Breaker.
Mike