Informational Guide

How To Stop A Toilet Tank From Sweating

If you have a humid bathroom, it’s likely you regularly see condensation on the tank. Follow this guide to stop a toilet tank from sweating.

by Ian Haynes

Have you ever walked into the bathroom to find that your toilet tank is sweating? This ugly situation is easy enough to resolve, provided you do not delay fixing it.

Read on to discover how to stop your toilet tank from sweating.

Any toilet can 'sweat' under the right conditions at any time of year. When the air in your bathroom is humid and touches the cold surface of your toilet tank, condensation forms and drips onto the floor.

This is because the water entering your tank is cold and cools the tank's surface down, making it easy to pull moisture from the air. Think of it as similar to the condensation on an iced tea in summer.

It is possible to buy an insulated toilet tank or insulation kit if needed. They are typically made of foam and designed to keep the tank surface at room temperature to prevent condensation. However, there are plenty of other ways to avoid this situation from happening in the future.

How To Stop Toilet Tank From Sweating

Why is There More Condensation on My Toilet Tank in Winter?

While condensation can occur at any time of year with the proper environmental conditions, it often happens in winter.

The room is warmer and often less exposed to the elements via the window, making it the perfect humidity and warmth level to create a sweaty tank. It is the same as if it were a hot summer with a cool toilet tank.

Don’t Ignore Tank Condensation!

While a few drops of water on a tank may seem harmless, condensation on toilet tanks can be severe if not dealt with quickly. Some of the long-term risks or issues include:

  • Rotted sub-floor
  • Damaged bolts holding the toilet to the floor
  • Mold
  • Rot
  • Soaked floor joints
  • Stained baseboard
  • Soggy drywall
  • Mildew
  • Discolored paint

How To Stop a Toilet Tank from Sweating (Step by Step)

Knowing how to fix condensation on toilet tanks is the first step to ensuring the damage to your bathroom (and your wallet) is minimal. Some ways to stop your toilet tank from sweating include:

  1. 1
    Line the tank with an insulation kit according to the product instructions, being wary of the floatation system.
  2. 2
    Check and adjust or replace the flapper valve.
  3. 3
    Install an anti-sweat valve according to manual instructions.
  4. 4
    Install or use a pre-existing exhaust fan after each shower
  5. 5
    Get a dehumidifier and place it above the toilet.
  6. 6
    Lower the toilet to avoid the rising heat.
  7. 7
    Install a low flow or insulated toilet.

Here are some tips for how to stop condensation on toilet tanks from occurring in the future:

  • Open your window or start the exhaust fan after each shower.
  • Take shorter, cooler showers.
  • Wipe down your walls with a towel after each shower.
  • Don't open the window if it is humid outside.
  • Place a towel or drip tray under the toilet and change regularly.

Sweating Toilet Tank Vs. Leaking Toilet Tank

One easy way to tell if your toilet is sweating or leaking is to wipe down the water and leave it for a while. If there is water on the outside of the tank that is dripping down, it is a sweating problem.

If the water is pooling under the toilet, then it may be a leak problem. Check your supply line, making sure to tighten and fill or replace if necessary. We also recommend tightening your t-bolts or replacing the wax ring if the leaks continue.

Condensation On Toilet Tank

People also Ask (FAQs)

Is an insulated toilet tank necessary?

That depends on your bathroom condensation situation. We recommend trying the other tips mentioned above before shelling out for an entirely new toilet or bathroom.

How do you tell if your toilet is sealed?

If you do not experience leaks or sewer smells in your bathroom, then your toilet is most likely sealed correctly. If you start seeing those things occur, inspect the wax ring at once.

How much water should be in a toilet tank?

That depends on how old the toilet is. Older models from 1982 and earlier require 5-7 gallons of water, much greater than the modern 1.6 gallons.


While a sweating toilet looks unpleasant, it is an easy thing to fix and prevent. We hope that following our tips for fixing condensation on toilet tanks will help you have a fresh and dry bathroom in the future.

Ian Haynes is an expert writer who has successfully deployed over 500 plumbing pages and other related content. He has an excellent understanding of home plumbing issues and translates his experiences via Plumbing Lab so readers can have a better understanding of common household problems. Outside of his work, Ian likes exploring Brooklyn with his Labrador.