Is there a product I can use to keep the soap scum off my shower walls?

There are many on the market. But if your shower walls are marble, you will have to use caution in choosing the proper cleaner, since most soap scum removers are acidic. Do not use an acidic cleaner on marble walls! If the tile is ceramic or granite, most soap-scum removers are safe to use. To prevent soapscum from developing, apply several coats of a good-quality silicone impregnator to the shower wall, making sure to cover the grout lines were soap scum tends to accumulate. It may also be helpful to apply a good marble wax on a regular basis.

TIP To prevent build-up of soap scum remove the water from the walls with a window squeegee immediately after showering.