How to Keep Your Shower From Getting Too Hot When Someone Flushes the Toilet
You're enjoying your shower, when all of the sudden, the water becomes scalding hot, forcing you to jump out of the way. Someone flushed the toilet again! If this nightmarish scenario sounds all too familiar to you, then it's time to do something about your hot shower problem -- before someone gets seriously burned. Here's a closer look at this problem and some ways you can solve it.
What causes the shower to blast hot water after flushing?
To understand the cause of this problem, you need to understand how your pipes are laid out. In most homes, there is a main water cold pipe with multiple branches coming off of it, along with a main hot water pipe with multiple branches coming off of it. If you use water from one branch, there will be less water available to flow down the other branches. For instance, if you flush the toilet, you use a lot of cold water -- and there is less cold water left for the shower.
Showers typically mix cold water with hot water. So, when you flush and use a lot of the cold water, less cold water comes through to the shower. The same amount of hot water keeps coming through to the shower, so the ratio of hot water to cold water is much higher than it initially was. As a result, your shower feels much hotter until the toilet finishes filling and there's more cold water available.
How can you prevent these hot water surges?
There are two main ways you can address this problem. The first is a bit of a quick fix that you can make on your own, and the second is a more involved project that may require the assistance of a plumbing service.
Reducing Water Flow to the Toilet
If you want to immediately stop your shower from shooting out hot water, you can do so by reducing the amount of water that the toilet uses. There will then be more water left over for the shower to use. The simplest way to do this is to turn the toilet's water supply valve to the left to close it partway. Your toilet will take a lot longer to fill, but your shower should stay cooler after someone flushes.
Note that there are instances in which this strategy won't work. If you have older, more narrow pipes that do not let a lot of water through at once, your shower may still surge hot after you flush -- even with the toilet valve partially closed.
Installing a Thermostatic Mixing Valve
This is more of a permanent fix that won't require you to slow down your toilet fill rate. If you have older, narrow pipes, it's really your only option. You can replace your shower's mixing valve, which is the valve that regulates how much hot and cold water is sent through the system, with a more modern thermostatic mixing valve. This type of mixing valve detects how much cold water is coming through the pipes and adjusts the supply of hot water accordingly. If the supply of cold water falls because someone flushed the toilet, the valve will cut back on the hot water supply, too. The water coming out of the shower should remain the same temperature.
If you are very handy, you may be able to replace the mixing valve yourself, but it is a project that involves cutting pipe and attaching new fittings to the pipe. In most cases, you are best off leaving this project to a professional plumber, who should be able to complete it within a few hours.
There's no reason to go on dealing with a shower that shoots out scalding water whenever someone flushes a toilet. Whether you adjust your toilet valve or replace your shower's mixing valve, the result will be a much safer, more enjoyable shower experience.
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