Install a Tray

Just as you slip a coaster under a sweaty glass to prevent condensation from leaving a wet ring, you can install a drip tray under the toilet tank to catch the excess moisture. It isn’t very attractive, and you’ll need to empty and clean it regularly. But as a cheap fix (under $10), it does buy you time to figure out a better solution.

Change Habits

If family members cooperate, you might be able to cure a sweaty toilet without spending any money.

  • Lower the room’s humidity by taking shorter, cooler showers, especially on hot, humid days.
  • Switch on that bathroom fan, and leave the door ajar so the fan draws in drier air from the rest of the house while it exhausts moist shower air. (Don’t open the bathroom window on hot, humid days; run the air conditioner instead.)
  • When possible, wait to flush until the room has dried out so you don’t fill the tank with cold water just when the risk of condensation is greatest.

Check the Flapper

Water trickling through a toilet not only wastes water and adds to utility bills, it also makes the tank colder — and more susceptible to sweating — because your tank is constantly refilling itself with cool water.

To check whether the flap is sealing, put a few drops of food coloring into the tank and wait an hour or so. If the color appears in the bowl, replace the valve and flapper — under $25 if you do it yourself. (First, be sure the fix isn’t even simpler, such as untangling the lift chain.)