Toilet Heaters, Personal "Offsets"

Back when I first wrote about the heat-wasting properties of toilets, I made a joke about “toilet-tank-water heaters”, a device so inane it could not possibly exist. However, I was later notified that such a device does exist– its purpose is to cure “problem condensation” on the toilet tank in summertime. The idea is that by mixing a percentage of hot water into the toilet tank, you prevent the sides of the tank from becoming cooler than room temperature after a flush, and thence prevent moisture from precipitating, dripping down, and causing problems. (In case you think I’m making this up, here’s an article on how to install one, from This Old House.) Of course, this magic comes at a price: unless you have solar hot water, you’re probably burning some sort of fossil fuel to supply hot water to the toilet tank. In summer.

Of course I was horrified to learn that people do this, doubly horrified when I learned that some of my own friends were already doing it, and triply horrified when I learned that another set of friends are installing the gizmos during their current bathroom remodel. To be fair, these last friends had a real problem. They live in Vermont, where it is fairly humid in the summer, and they do not use air conditioning, so their house is not artificially dehumidified. Moreover they have well water, which is very cold entering the house, and unlike many New Englanders they do not have a cellar– so there is no long stretch of pipe in an unfinished area where the water would warm a bit before entering the toilet. Lastly, they both work from home much of the time, so they use their toilets more than most of us. As a result of all this, their toilet tanks dripped incessantly during the summer. They had damage to their floors, peeling paint behind the toilets, mold and mildew, and other real issues. So, when they set out to remodel the bathrooms this fall, they put in the toilet-hot-water piping.

Needless to say, I gave them some crap. I felt that there were greener ways of solving this problem (e.g., how about a diverter valve for summer use that sends incoming cold water to a short outdoor coil before it goes up to the house for use? Or toilet tank insulation?) I set about number-crunching to find how much fuel they were going to burn making extra hot water for their toilets every summer. After making various reasonable assumptions, I concluded that they will use roughly two gallons of propane more each summer heating their toilet water. Horrifying.

But, my friend pointed out, shouldn’t they get some credit for simultaneously replacing their existing 3 gallon-per-flush toilets with new low-flow dual-flush toilets, which use only 0.9 or 1.6 gpf? I grudgingly conceding this might be true, and again set about data-crunching to determine how much heating fuel they will save in winter by having smaller flushes. And in fact, I found they will save roughly seven gallons of propane per winter. Thus, the net effect of their renovation is an annual savings of five gallons of fuel. And me left with little to poke fun at.

However, this net savings is largely due to the length of Vermont winters and brevity of Vermont summers. If you are much south of here, you won’t be able to do the same trick. Also, if you already keep your house cold in the winter, the fuel returns on the low-flush toilet start to diminish.

Finally: I am predicting that the smaller-flush toilets alone will cure my friends’ condensation problem, even if they don’t use the hot water mix-in. I am curious to see if this turns out to be true.


2 Responses to “Toilet Heaters, Personal "Offsets"”

  1. Doug Says:

    Why not insulate the toilet tank? Wouldn't that reduce the rate of heat loss, thus increasing the surface temperature of the tank to something above the dewpoint?Sure, the water will heat up *eventually*, but the rate is what's important in this case.

  2. Turbo Says:

    Oh, definitely, I agree that would be the best solution, and I did suggest it to my friends– but they did not approve the idea. Can't remember why; maybe they already had the warm-water hardware installed.But there are kits available for toilet insulating (e.g., or I'd think a bit of scrap polystyrene and some waterproof adhesive would do the same. Also, my Canadian friends report that many commercially available toilets sold there come with insulation built-in already. Not here, though, apparently.

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