How To Stop Condensation On Toilet Tank

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.

Why Does My Toilet Tank Have Condensation?

When the weather turns hot and humid, there’s a lot of moisture in the air. At the same time 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. Several manufacturers make toilet-tank insulators they claim cure sweaty toilets, but most don’t work very well.

Two Ways To Stop Your Toilet From Sweating

There are only two surefire ways to stop your toilet sweating:

1. Dry Out the Air in the Bathroom

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.

2. Install an Anti-Sweat Valve

Install an antisweat valve in the water-supply line leading to the toilet. An anti-sweat valve adds a little hot water to the toilet water 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. Selecting Your Valve Anti-sweat valves are sold at home centers and plumbing-supply dealers in both adjustable and preset types. When selecting your valve, 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.

How Do You Install an Anti-Sweat Valve?

There are three stages for anti-sweat valve installation: preparation, valve installation, and the temperature check.

Prepare

Install the Valve

Do a Temperature Check

How to Fix a Sweating Toilet Tank