Many of us have experienced this phenomenon, whether at home or while traveling: Someone flushes the toilet, and suddenly the shower temperature drastically changes – sometimes it gets freezing, or sometimes all too hot.

It’s an unnerving situation, but there’s a reason that it happens, and even some ways to make sure it happens less often. Here’s what you should know.

Showers Getting Hot When Toilets Flush

It may last only a few seconds, but no one likes getting scalded by an unexpected burst of boiling water! If you find that this happens when someone flushes a nearby toilet, you probably have a “trunk and branch” plumbing system. That means your home has one large plumbing pipe running through the house to provide water, with smaller pipes sprouting off to various rooms. So many of your appliances share at least some of their water with the whole.

This causes problems with shower water, which is usually a mix of hot and cold water from the system. Toilets, on the other hand, only use cold water when flushing. So a toilet that suddenly flushes a large amount of cold water is taking that cold water from the pipes around the shower…leaving the shower with only purely hot water for a brief time.

The easiest way to address this problem is to look into a low-flow toilet that fills more slowly after flushing, which tends to mitigate the issue. There are also shower retrofits that can address this issue if it’s very annoying.

Showers Getting Cold

Suddenly cold showers are a shock to the system, and not always a pleasant one. However, this doesn’t usually have much to do with toilet flushing, although it does also occur in trunk and branch systems where all the water in the house is connected via a mainline.

When this happens, someone else in the house may be using hot water. It could be the dishwasher, someone running hot water while brushing their teeth, the washing machine drawing on the waterline, or other various causes. This draws on the shared hot water, and if the draw is large enough, then the shower will suddenly find itself short of the right mixture of hot water, and things get cold. It’s not a good idea to change shower temperature immediately because it can resolve quickly.

Fixing this issue is difficult because it’s hard to give a house-wide command not to use hot water when someone is taking a shower. Instead, a thermostatic mixing valve for the shower may be able to help address the problem.

Are temperature changes in the water around your house starting to annoy you? There could be a variety of reasons your plumbing is doing this, including problems that can be fixed or addressed with the right equipment. To find out more or arrange for a serious plumbing inspection to finally get down to the bottom of it, contact Amanda Plumbing together to get rid of temperature shock!