Toilet Condensation Q&A

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Dear NH,

The toilet in our house has a lot of condensation on the bowl. It is actually leaving fairly large puddles of water on the floor. What's causing this and do you have any ideas on how to fix it?

JS from Ontario, Canada


Condensation on a toilet tank is caused by the water in the tank cooling the surface of the tank. This causes water vapor in the air to turn back to liquid water upon contact with the cool ceramic surface.

There are a few different ways to deal with this problem. The first is to increase the water temperature in the cold line. This can be done by installing a mixing valve between the hot water heater and the cold water line to the toilet. The valve will add a little hot water to bring the temperature up. I don't suggest doing this for your entire home water system, since hot water carries more mineral contaminants and is usually not recommended for drinking water.

There are some solutions right at the toilet tank. If you have a fairly new toilet, you may be able to purchase a replacement tank that is lined with plastic foam insulation. This will cut down on much of the condensation by keeping the temperature on the outside of the tank closer to room temperature. You can purchase a toilet tank liner kit at the hardware store that allows you to do the same thing to virtually any toilet. However, your installation must be scrupulous… if there are any leaks of water through the installed foam to the tank the EFFECTIVENESS of the installation will be compromised!

The easiest, though least effective route, is to purchase a toilet tank drip catcher. These devices mount under the tank, catch the dripping water and direct it to a pan or jar on the floor. You might have to hunt for the right one of these, as they don't necessarily fit on all toilets.

Of course, there is the old standby… put a towel on the floor under the toilet and change it regularly so it doesn't mildew! Putting a piece of plastic (such as a trash bag) under it will help keep the floor drier.

Dear NH,

On your page about toilet dripping... a.k.a condensation on the toilet tank... you described the damage which can and will follow if something isn't done about it You also gave three fixes to the problem. All three fixes are rather difficult to do, sloppy to deal with or rather expensive.

May I offer a suggestion that has served me very well in a high humidity area that DOES cause an abnormal amount of dripping? It's called a toilet tank cover, a little rug that wraps around the tank itself and a tank lid cover. They coordinate with the contoured carpet around the toilet base, a rectangular bath carpet, and a toilet seat lid cover, too.

After applying the tank wrap carpet, the tank itself is insulated well enough not to cause any condensation. If there s any condensation, the contoured carpet around the base of the toilet would be more than enough to catch it and allow it to evaporate quickly, saving the floor from rotting out. No special tools are needed and even the least mechanically inclined housewife can install one in a matter of seconds if not only a minute or two.

Besides if the condensation gets really bad one day, a simple trip to the washroom and a spin in the dryer, and the cover is good as new! If you have a difficult color you need to match, get a white set and dye it. A simple and cheap approach to a nasty little problem.

The down side of this is the lack of availability. I've been searching high and low for one of these ensembles for over a month now!



Thanks for the info. You know... I thought I mentioned putting a carpet or towel under the toilet tank (a solution which is a little less stylish but even simpler than yours)... but I realize now that I mentioned this in a Q&A, not in the article! Silly me! Covering the outside of the tank should reduce the total condensation, though... a definite plus!!

I ran upstairs and blew the dust off the latest JC Penney catalog and, lo and behold, they sell "toilet tank sets"... carpet that covers the tank and the tank cover... for around $20.00. You're right... a very reasonable and easy fix. And you could always throw a coordinating towel on the floor, right?

Just two other quickies. First, most "housewives" I know are at least as "mechanically inclined" as their husbands if not moreso... it's called homeland survival!
Second, don't talk to me about toilet seat covers! Most of us guys don't like 'em for one reason... once they are installed the seat won't stay up... making them "inconvenient" to use. Nothing like a toilet seat banging down to wake up the family!  'Nuf said.