Is there any way to prevent condensation on the toilet flush tank in the bathroom?

I know it's not like condensation in other rooms (bedroom, etc.), because the hot shower in the bathroom causes a lot of water molecules in the air, which are mostly hot. The water in the toilet flush tank is cold, and because of the temperature difference there will be condensation on the outside of the flush tank. Any way to prevent this?

This is an age old problem in cold countries so I'm guessing someone must have found a solution. (I recently moved from a tropical country to a cold country.)

  • This isn't an issue with modern cisterns because they're made of plastic and not metal, and was only a problem previously in unheated toilet cubicles or bathrooms.
    – Bamboo
    Jan 15, 2015 at 14:23
  • @Bamboo plenty of new toilet tanks are still made from steel. I have two new ones that are, and in one case the room isn't heated very well, so there is a lot of condensation there when someone takes a shower. I think still an issue for some folks.
    – J. Musser
    Jan 15, 2015 at 17:36
  • 2
    I've often thought that the cistern should be plumbed to fill with HOT water as well as cold - and a diverter valve to switch between summer/winter. It would give multiple benefits: 1. No condensation 2. Warming the bathroom 3. Help to flush the cold water from the hot pipe so sink runs hot quicker.
    – Lefty
    Jan 15, 2015 at 21:40
  • @Bamboo most cisterns are actually made out of vitreous china, not plastic. At least this is true in the states. Jan 16, 2015 at 13:59
  • 4
    A lot of condensation may be a sign that your toilet is continuously filling and never warming to room temperature. I would check for signs that the toilet is overflowing quietly into the bowl. Jan 16, 2015 at 15:45

3 Answers 3


Most bathrooms have an exhaust fan in them. The fan should be turned on when you start the shower, and it should remain on for at least a half hour after. This will greatly reduce the amount of condensation you have on your toilet.

  • 2
    Or, if you can, open a window.
    – fredley
    Jan 16, 2015 at 14:04
  • 1
    Especially extractor fans with in-built humidity sensor which removes moisture and mould.
    – kenorb
    Jan 16, 2015 at 18:56

Try waxing the tank with car wax or other car polishing product. These products often contains additives that help water bead up and resist condensation.

  • I recently used SC Johnson paste wax on pretty much everything in my bathroom recently, and it does a great job keeping things clean. You can pretty much use it on everything. You just have to make sure that you don't leave it on too long because the residue can be hard to remove. Jan 16, 2015 at 20:35
  • Interesting, I read many decades ago that washing your bathroom mirror with shampoo (or other liquid detergent) and then rinsing it clean with a minimum or water needed to remove the suds would leave a film on it that resisted visible condensation as the surface tension was lost and the moisture was absorbed by the detergent film.
    – KalleMP
    Oct 19, 2019 at 13:03

I ran a mix of hot and cold water to my toilet. No more condensation at all,and no mould around or under the toilet even where you cant see it. No more cold toilet seat. Instant hot water to the sink after a flush. Well worth it!

  • This gives ideas. If one wanted to go to extremes one could plumb a loop of the underfloor heating piping through the cistern so that it was always a bit above room temperature.
    – KalleMP
    Oct 19, 2019 at 13:06

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