Fixing Toilet Tank Condensation

MOTHER EARTH NEWS readers receive guidance on condensation in a toilet tank, including tests to make on toilet parts and room temperature changes.

| January/February 1987

I have a problem with condensation from my toilet tank. We want to put an oak floor in the bathroom, but we're afraid the toilet tank condensation will ruin it in no time. Meanwhile, we keep a long pan on the floor to catch the drippings. Any suggestions?  

Fixing Toilet Tank Condensation

First, make certain the toilet tank condensation isn't coming from a hairline crack in the tank — or from a damaged ballcock valve or seat, which could spray water onto the lid and down the outside of the tank.

If you've determined that the tank is indeed sweating, try lowering the temperature of the bathroom and the surrounding area and reducing the humidity of the room with a dehumidifier or a ventilating fan. In addition, you could install a plastic tank liner to insulate the tank walls from the cold water.

Richard Freudenberger, research coordinator
5/27/2018 10:14:22 PM

I used the plans at WWW.EASYWOODWORK.ORG to build my own – I highly recommend you visit that website and check their plans out too. They are detailed and super easy to read and understand unlike several others I found online. The amount of plans there is mind-boggling… there’s like 16,000 plans or something like that for tons of different projects. Definitely enough to keep me busy with projects for many more years to come haha. Go to WWW.EASYWOODWORK.ORG if you want some additional plans :)

Paul Myers
6/30/2012 2:46:03 PM

Another solution is to place an adjustable mixing valve between the toilet and the water supply. This valve has inputs for both hot and cold lines, and can be set to a temperature that is above the dewpoint in the house. 70 degrees is usually good enough to prevent condensation unless your house is REALLY hot and humid. This will work better than running straight hot water, which wastes energy, and heats your house, and is simpler than adding another tank, which will probably spring a leak someday.

6/27/2012 8:42:17 PM

Wrap the tank with a thick towel.

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