Hard water leaves its mark on shower walls and glass-shower enclosures in the form of crusty little white lime deposits that sometimes seem as though they're going to be impossible to remove. Here are a couple of our secret formulas that should help: Sodium carbonate is the chemical you're looking for. It's the base for many cleaners and is the primary ingredient in washing soda. If a strong solution of sodium carbonate doesn't do the trick, try a squirt of liquid toilet bowl cleaner. Bowl cleaners are strong dangerous chemicals, so use them with eye-and-skin protection and plenty of ventilation. Once the water stains are gone, apply a coat of car wax to all the surfaces in the shower. Doing so will make cleaning a breeze next time. And that's the On The House tip for today.