Water Goes Hot to Cold?

Have you been in the middle of an enjoyable shower, only to be shocked by super hot water that then turns colder?

Problem: Shower Water Suddenly Gets Hotter and Then Colder When Someone Flushes the Toilet

If you are getting shocked in the shower with blasts of hot and cold water when someone flushes the toilet, your water delivery system is set up in a trunk and branch configuration. That means you have one large pipe running from one end of your home to the other with smaller pipes branching off to individual appliances and faucets.

When one branch needs water (such as someone flushing the toilet), that branch suddenly siphons off some cold water. Your shower gets hotter for a moment while the toilet fills (and the cold water is sent to the toilet), but then that cold water becomes available again, mixing with the hot water going to shower, resulting in a drop in temperature.

In some cases, you’ll discover you suddenly get blasts of cold water while taking a hot shower. This happens when someone uses another appliance or faucet that requires hot water, like the kitchen sink, the dishwasher or even the clothes washer (if it is set to warm or hot.)

You can get scalded by blasts of hot water if your water heater isn’t set to a low enough temperature. Be sure to pay attention to the scalding warning on the heater if you are at risk of getting hot water blasts. If you are at risk of hot water blasts, keep the water heater set to 120 degrees to avoid scalding.

Solutions to Temperature Fluctuations in the Shower Caused by Toilet Flushing

You can solve this problem one of four ways.

1. The cheapest way to solve the problem is to close the water supply valve (just a little) to slow down how quickly your toilets fill with water.

2. You can also install a mixing valve, which will balance the mixing of the hot and cold water regardless of fluctuations of use.

3. You can also replace your toilets with low-flush toilets, which require less water. This will make it such that less cold water is siphoned off whenever someone flushes, resulting in a smaller change in shower water temperature. This will also lower your water bill and benefit the environment.

4. If you live in an older house and need a major plumbing overhaul, you can talk to your plumber about widening the main trunk pipe or revamping the water delivery system to include a central load balancing manifold. Your plumber will know what you’re talking about, and you’ll take care of your temperature fluctuation problems.

Need Help With Water Temperature Problems?

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Water temperature problems in shower?

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Article Summary

Quick question & answer: Why is my shower water suddenly getting hot?

Your shower water is suddenly getting hot because either the water heater isn’t set to a low enough temperature, causing it to scald you at times, or, because someone flushed the toilet. If it happens when someone flushes, cold water is going to the toilet to fill it, causing your shower water to temporarily heat up.