A Fix for a Sweating Toilet

Learn how to solve an uncommon toilet problem.
hot toilet seat

What to do when the toilet is warm to the touch.

We have a 1930s camp in the mountains, where temps sometimes drop below zero in winter and the bathroom gets chilly. During a cold snap, we noticed the water in the toilet was hot, as if the plumber had deliberately switched the lines. Sometimes the seat is actually warm to the touch! We wonder whether the toilet was deliberately plumbed this way to keep it from freezing in subzero weather. —Jim Scamman

The Fix

The reason you have hot water in your toilet isn’t because someone wanted to keep the water from freezing. You have a problem that should be addressed. Background: Most toilets have mixing valves to prevent condensation, allowing some hot water to flow into the cold water line to warm it. When the water leaks in continuously, however, the hot water dominates the cold and you get a tankful of hot water. It’s not bad for your toilet, but it could be hazardous to your wallet, running up your utility bill.

If the water in the toilet has always been hot, the hot and cold water lines running to the toilet may indeed have been installed incorrectly—something that a good plumber can fix. If the problem surfaced more recently, it’s more likely the cause is a bad flapper or a bad fill valve. To check, remove the tank lid and flush the toilet. If the flapper doesn’t seat properly after it has dropped, the toilet will keep running: water will continue to enter the tank and flow out of the overflow tube. To fix the leaky valve, adjust the float level using the fill valve’s water adjustment clip or arm. For a float-cup valve, squeeze the two sides of the metal clip together, then slip the clip down the rod. If it’s a float-ball valve, lower the water level by bending the float arm slightly downward.

If the toilet refills properly, test it for a bad flapper by adding a few drops of food coloring or a colored dye tablet (find at a hardware store) to the tank water. Wait 20 minutes. If any trace of colorant appears in the toilet bowl, you’ve found the source of the leak. Replace the flapper, or have a plumber replace it for you.

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