A: George, please send my apologies to your wife since you should not have to remodel your entire tub and shower unit.

First, nice job on wanting to update your old three-handle shower valve. Older tub and shower valves without scald protection can be very unsafe. In most areas of the country, codes require that you install new shower valves with scald protection, so you're doing the right thing for your home and family.

Your issue is very common since most one-handle shower valve cover plates are about 6 - 7 inches in diameter, and the spread needed to cover an old three handle valve is about 10 - 12 inches. Since it is a common plumbing problem, some manufactures do make larger special order cover plates; contact your valve manufacturer to see if one is available.

If not, there is a backup trick that plumbers use. You need to find a plumbing supply house in your area that carries a "remodeling plate" or what many plumbers call a "goof plate." This is a large stainless steel plate shaped kind of like a football. This plate should cover all the existing holes and allow mounting of the new valve as well. I've personally installed many of these kits, and they do the trick as long as you follow the manufacturer's instructions.

Also, with the money you save, I highly recommend you get your wife something special so she'll love the new shower valve as much as you do!