Repairing a sweaty toilet
HOLD THE valve against the cold-water line and mark where its center outlet port aligns with the vertical pipe.
Summer is the season for backyard barbecues, days at the beach and family vacations. Unfortunately, sweaty toilets are another sign of the season. In fact, every summer millions of homeowners have to deal with toilets that perspire puddles of water onto the floor.

This problem is much more than just a mild annoyance: Condensation running down the toilet can seep under the flooring, rot the plywood subfloor and soak into the floor joists. It can also stain baseboard molding, turn drywall soggy and discolor wall paint with mildew.

When the weather turns hot and humid, there's a lot of moisture in the air. Meanwhile, the water entering the toilet tank is comparatively cold -- about 50° to 60°F. When the warm, moist air hits the cool porcelain toilet surfaces, the air condenses, turns to water and soon drips onto the floor.

Although a toilet sweats only on warm, humid days, it can drop a surprisingly large amount of water in a very short time.

Just add Heat

Several manufacturers make toilet-tank insulators they claim cure sweaty toilets, but most don't work very well. There are only two surefire ways to stop toilets from sweating. First, use an air conditioner or dehumidifier to dry out the air in the bathroom. However, this approach won't work if you don't have one of these units or don't want to run it all summer.

The second method involves installing an antisweat valve in the water-supply line leading to the toilet. The valve adds a little hot water to the line, which raises the water temperature in the toilet enough to warm up the tank and bowl. That's all it takes to keep condensation from forming, even in the most sultry weather.

Antisweat valves are sold at home centers and plumbing-supply dealers in both adjustable and preset types. Pay the extra $10 or so for an adjustable model. It allows you to regulate the water temperature and shut down the hot-water side completely when it's not needed. For our installation, we chose the Adjusto-Temp adjustable toilet valve, from Universal Rundle (Model 5025-1, $33). This valve can be installed in the bathroom, behind a wall or below the floor (if there's a crawl space or basement). Here, we show cutting the valve into a water-supply line in the basement directly beneath the toilet.

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