Sweating Toilet Tanks
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Sweating Toilet Tanks

Q: Do you have any advice for dealing with sweating toilets? Other than the Styrofoam that you glue in, is there anything else that might work? And if the Styrofoam is the only answer, how well does it work and is there a problem using it with the water-conserving toilets? — Barb Wolfrum; via e-mail

A: Unlike a dewy glass of ice tea on a balmy day, sweat on the tank of a toilet is not aesthetically pleasing. It’s a maintenance issue, too, because the dripping water can wreck the floor beneath it. Even though it may not be the most pressing fix-up issue, it’s best not to ignore it.

Toilet sweat is condensation caused when the water inside the tank is markedly cooler than the air outside the tank. This sweating can be addressed in a number of ways ranging from cheap fixes that are mostly cosmetic to more spendy approaches that are permanent. (The Styrofoam inserts you reference fall somewhere in the middle).

Here are five fixes.

Let it flow . If you are the type of person who puts duct tape on your broken eyeglasses, this is the fix for you. Many people simply put a drip pan under the tank to catch the excess water as it sweats off the tank. It’s straightforward, quick and cheap. It doesn’t change the appearance of the wet tank, however, and it also adds a pan on the floor to the bathroom décor.

Soak it up. Another approach that treats the symptoms and not the disease is getting a toilet tank cover. Covers fit like a jacket over the tank and absorb the extra water. On the plus side, getting a cover is not labor or finance intensive. On the not-plus side, the cloth-covered toilet tank look went out in the ’70s.

Insulate. Installing a foam product to insulate the toilet tank is a moderately taxing home-improvement task that should keep the tank dry by separating the tank water from the tank sides. Hardware and home improvement stores carry kits that include foam and instructions; they generally sell for under $20. You’ll need to drain the tank and dry it with an old towel. To completely dry the inside of a tank, carefully use a hair dryer. Cut the foam pieces to fit your tank, test-fit them to their respective sections, and then secure them with adhesive. Expect to wait a half-day for the adhesive to dry before refilling the tank for use.

Temper it. Mixing in a little hot water to the tank gets to the root of the condensation problem. Installing a temperator valve, which requires both hot and cold water supply connections, can help regulate the temperature differential between inside and outside the tank. Unless you are especially adept at plumbing projects, this is probably a task best left to a professional.

Start Over. If your resources permit, you may wish to simply buy a new toilet. We’ve heard great reports about low-flow toilets with built-in foam insulation. Power-assist toilets – which use compressed air to turbocharge each flush – also are low sweaters. A pressure tank within the main toilet tank provides insulation. Expect to pay about $100 extra for a power-assist toilet.  

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