What Causes a Toilet Tank to Sweat?

On especially warm days or after a nice hot shower, you may find that you are not the only one that is sweating in your bathroom – what is going on with your toilet? Your first instinct may be that it is leaking somehow, but it does not seem worse after flushing, and the water level and everything appear to be normal. But can a toilet really sweat? If so, what causes a toilet tank to sweat?

toilet tank to sweat

If you want to know what causes a toilet tank to sweat and how to fix it, you have come to the right place!

What causes a toilet tank to sweat is essentially the difference between the cool water on the inside of the tank and the warm, moist air in the rest of your bathroom. Basically, your tank has the cold sweats. The process of the warm air hitting the cool tank creates condensation, which results in what appears to be a sweaty toilet tank.

Want to learn more about what to do about the condensation on your toilet? Keep reading for our tips and tricks!

Related: What’s the difference between Toilet Chair and Comfort Seat Height?

How Do You Stop a Toilet Tank from Sweating?

There are a variety of things you can try to stop a sweating toilet cistern.

1. Reduce Moisture in the Bathroom

The first thing you should try is reducing the heat and humidity in the bathroom.

  • Install an air conditioner or dehumidifier
  • Keep the door open while showering (or at least when you finish)
  • Take quicker and/or cooler showers
  • Dry the walls after a shower
  • Use the exhaust fan during showers
  • Open a window in your bathroom on cool, dry days*

*Though it may still seem like it is helping, if there is any humidity in the air outside, do not open the window!

2. Insulate Your Toilet Tank

Since the sweating is due to the warm, humid air condensing on the cool porcelain of the toilet, warm up your toilet tank to reduce sweating. You can likely buy a toilet tank liner insulation kit at your local hardware or plumbing supply store. It can be quick and easy to insulate your tank.

How Do You Insulate a Toilet Tank?

Step 1: Empty and Dry the Tank

Use the water shutoff valve and flush to get rid of most of the water.

Step 2: Cut Insulation

Use scissors to cut the insulation to the size of your tank.

Step 3: Peel Protective Sheet

The insulation provided in these kits are typically closed-cell foam with an adhesive backing. Peel off the backing to expose the adhesive side.

Step 4: Apply to Tank

Stick the properly sized insulation pieces to the inside of the tank.

Related: What Causes Brown Water in the Toilet?

3. Wrap Up Your Toilet Cistern

Instead of lining the inside of your tank, you could try warming it up from the outside. Wrap up your cistern in a premade tank cover or other piece of fabric. Terry cloth is usually a good choice of material for this purpose, as it will absorb any condensation that develops on the tank. Note that mildew can build up on this after a while, making sure you wash it roughly once a week.

4. Install an Anti-Sweat Valve

An anti-sweat valve, or mixing valve, connects the hot water line to the cold water line that goes into the toilet. The valve allows some hot water to mix with the cold water before entering the tank, thereby warming up the water and reducing condensation.

5. Install a Tempering Tank

The principle behind this is similar to that of the anti-sweat valve in that it helps warm up the water before it goes into the toilet tank. In this case, though, the cold water line is attached to a separate tank that heats the water.

6. Buy a New Toilet

If all else fails and you cannot seem to control the condensation levels on your toilet, you can always buy a whole new toilet. Consider investing in a tankless toilet, for example. Though they can be expensive, they move water in and out of the toilet using an electric pump and are not prone to the same condensation issues.

If a tankless toilet is not for you, you could buy a new low-flow toilet as they use less cool water to run, which results in less condensation. Today’s low-flow toilets also tend to come standard with insulated tanks, which will also reduce the likelihood of a sweaty toilet.

Related: What are the different Types of Toilet Flush Systems?

Can I Install a Drip Tray?

You certainly can – it just will not stop your problem of a sweating toilet tank. A drip tray will just catch the water coming off your toilet and prevent it from damaging the floor. If you are waiting to install a more permanent solution to your sweating problem, a drip tray can be a good way to prevent water damage to your floor in the meantime.

flush toilet flushing mechanism vector diagram

Is My Toilet Leaking or Sweating?

If you are experiencing condensation on your toilet, it is likely due to sweating. However, it is entirely possible that your toilet is sweating due to a leaky part in your toilet tank: the flapper valve.

Your toilet flapper valve could be what is leaking, which means that your tank will be constantly taking in cool water to replace the water that is leaking out. To check if your flapper is leaking, try the following method.

Step 1: Add Food Coloring

Add a few drops of food coloring to your tank. This will allow you to tell if the water is leaking into the toilet bowl.

Step 2: Wait

Do not use your toilet for about an hour. After that, come back and see if there is any colored water in your toilet bowl. If there is, you may need to adjust or replace your flapper.

Can a Toilet Leak from Condensation?

leakage water toilet due blockage pipe

While it may appear that your toilet is leaking at its base, condensation by itself cannot cause a leaky toilet. However, you may eventually have leaky floors due to water damage from your sweaty toilet. Moisture on your floors can also be a breeding ground for mold and bacteria, so it certainly is important to take steps to prevent your toilet from sweating.

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