In many older houses or in remodeled bathrooms, it is common for the bathtub to double as a standup shower. When installing the shower, however, it wouldn't be efficient to create an entirely new water supply pipe to feed the shower head. That's where a diverter valve comes in.
A shower diverter valve can come in a few different forms, but they all share the same purpose. The diverter may appear as a pin pulled upward from the bathtub faucet spout, it could come in the form of a third (middle) faucet handle, or it might be a button that has to be pushed or pulled that is located right around the faucet itself. In any case, this valve works to divert the flow of water from the bathtub faucet to the shower head. The operation of the device is simple - pulling the pin or handle engages a rubber stopper, which causes the water to flow in a different direction. The pressure created by the action forces the water up toward the shower head, allowing you to enjoy a nice shower from inside a typical bathtub.
Being such a simple part, it's not often that a shower diverter valve will fail or break. However, like any moving part, it can and will wear out over time. it is usually easy to tell when this has happened. The most common and obvious sign that the diverter valve has failed is when water continues to flow out of the lower bathtub spout, even though the valve should have engaged the shower head only. This is usually caused by an incomplete seal around the inner stopper, which isn't fully blocking the flow of water out of the faucet. These rubber stoppers can become worn with age, whether due to calcium deposits from hard water, or simple wear and tear.
A professional plumber can fix shower diverter issues in a snap. It will involve simply disassembling the diverter apparatus and cleaning or replacing the rubber stopper. A plumbing professional might also take this opportunity to inspect other O-rings and gaskets around the faucet, including those in the faucet handles or around where these components attach to the water supply pipes behind the wall.
Before a leaky shower starts to get on your nerves, call up your local Roto-Rooter plumbing professional today and schedule a repair.