Why Is There Hot Water in My Toilet?

by Michael Franco
illustration of steam escaping a toilet

Having hot water in your home allows for a hot shower after a hard day’s work, is a real help when scrubbing dishes and brightens whites in the wash. But hot water in the toilet? Now that’s not something any of us want or need.

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And yet.

Hot water can make its way into your toilet for a couple of different reasons. So, if you realize your toilet has hot water in it, you’ll need to do some troubleshooting as to why it’s there so you can get to work on fixing it. Depending on the problem, it may be a quick fix you tackle yourself. But in some instances, you may need to call in a plumber.

There’s Hot Water in My Toilet!

Hot water in your toilet won’t actually damage your toilet, but you’ll still want to fix it — and not just because having hot water in your toilet seems weird. The excess hot water flowing into your toilet is a waste of energy and can actually cause your utility bills to increase, which is never fun.

There are three main reasons why you might have hot water in your toilet:

Hot and Cold Water Line Issue

If you’ve just moved into a brand-new home or have a newly installed toilet, the hot water problem could be that the hot and cold water lines simply weren’t installed correctly. In this situation, you can have the plumber who installed the toilet come back and correct the issue. If, however, you have a hot water issue arise with an existing toilet, you’ll need to keep troubleshooting.

Problem with the Flapper

If your toilet’s flapper is not working properly, it can cause water to continue to flow slowly into the tank. If your toilet keeps filling with hot water, it may mean you need to adjust or replace your flapper.

If you’re like most folks, you probably haven’t given much thought to your home’s toilet flappers, much less to replacing them. But flappers can corrode over time and, as a general rule, should be replaced every four to five years. Luckily, a worn flapper is an easy, inexpensive fix, and you can try replacing it on your own and see if that remedies your hot water problem. Flappers are typically black or red rubber orbs, and you can buy a replacement for under $10.

You also want to make sure the flapper is hooked to the chain at the correct length to allow for proper opening and closing. Does your flapper lie flush when your toilet has finished flushing? If the flapper is connected too high on the chain, it might not be closing completely, causing the water to continue flowing. You can adjust this easily by unhooking the clasp and relocating it to another spot on the chain until the flapper closes as it should.

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Bad Fill Valve

A bad fill valve can also allow water to keep leaking into the tank, leading to a hot water issue in your toilet. Mixing valves work to coordinate a perfect combination of hot and cold water with each flush that helps prevent condensation, also known as “toilet sweat” (ew).

Sometimes called an “anti-sweat valve,” a mixing valve should, by design, make the toilet tank water lukewarm, but not hot. This means your toilet must be connected to your hot water supply via a hot water line to allow for this mixing. But if the fill valve isn’t working properly, it could allow more hot water in than is necessary, leading to a hot-water-in-the-toilet problem. Unfortunately, a fill valve repair or replacement is far more involved than simply replacing a flapper, so you’ll more than likely need to call in a plumber for this particular fix.

Hot and Then It’s Not

Okay, so maybe “Why is my toilet water hot?” wasn’t a question you ever expected to ask yourself, but homeownership comes with all sorts of surprises — not all of them welcome. The good news is that, in the grand scheme of home issues and repairs, hot water in your toilet is a relatively easy problem to address. Whether it requires calling in a plumber to replace the fill valve or rework water lines, or if it's simply a matter of replacing the toilet flapper yourself, with a little work, the hot water in your toilet should soon be a thing of the past.


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