How to Stop Your Toilet Tank From Sweating

How to Stop Your Toilet Tank From Sweating
Photo: BiroZsolt, Shutterstock

Along with all the fun in the sun and taking advantage of the extended evening daylight, summer also means sweat. Sure, sweating isn’t limited to December, January, and February, but when the temperatures climb, so too does the tendency to turn into a sweaty mess.

And just because it’s natural, that doesn’t make it any less embarrassing. When people see excessive sweat, they may wonder if there are any underlying issues that have the potential to resurface as more serious problems later on. Plus, it’s no fun being perpetually moist. We’re talking, of course, about toilet tanks. Here’s what to do if yours is sweating a lot.

Why do toilet tanks sweat?

Before getting into solutions, let’s talk about what causes condensation to form on the outside of toilet tanks in the first place. Here’s how Merle Henkenius explains it in an article for

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 10-15C. 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.

How to stop a toilet tank from sweating

According to Henkenius, there are two possible solutions to your toilet tank’s perspiration problem.

Keep your bathroom dry and cool

Before taking the time and energy to do a whole plumbing project, you can start by attempting to control the humidity and temperature in your bathroom by using a dehumidifier and air conditioner, Henkenius says. But not everyone has these appliances sitting around, and even if they do, running them all summer can get costly.

Install an anti-sweat valve

For a more permanent and sustainable fix, Henkenius suggests installing an anti-sweat valve in the water-supply line leading to the toilet. And what will that do? Per Henekenius:

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.

The installation can be a bit of a process, so if you opt to do it yourself, Henkenius walks you through each step here.


  • Which state is this predominantly???
    Certainly not in WA during summer periods!

    Just like several other tap/plumbing… For first 30-60 seconds, you get water at 30+ degrees, even though cold tap (hence needing to run for ages first, before can get a glass of water – as water thats been in pipes) – same would go for toilet plumbing, except that, toilet cisterns usually fill in that timeframe prior to cold water flowing through (unless you are someone that needs to do several “full flushes” each time).

    Unsure where origonal article got water temps of 10-15 degrees????
    Certainly not during summer, and certainly not in WA.

  • By the way – article references a US site… And on that site, it talks about toilets having both HOT + COLD water inlet pipes… Something i had never heard of existing here in AU.

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