Hopefully, you have not experienced a sudden cold shower just because someone came in and flushed the toilet in your bathroom.

Why Does Flushing The Toilet Make The Shower Water Cold?

But if you have - you know it's not an experience you would wish to repeat.

So, what causes this and what can you do about it?

The answer is typically old shower valves and/or poor plumbing.

Is It The Shower Valve?

A shower valve works in the following manner:

  • Water pressure changes in the hot / cold water supply line
  • This causes a piston to open or close a small port so that the water pressure remains balanced
  • The balanced water pressure keeps the water flowing at the temperature you set
  • If there's a problem with the shower valve and it's piston - then your water temperature will fluctuate

If your valve in the shower has worn out or is defective, when the water pressure in your water line changes due to a toilet being flushed, the water coming out of your shower head will fluctuate and get either colder or hotter.

Know that it doesn't have to necessarily or always be a result of the toilet flushing. Running the dishwasher or washing machine while you take a shower may do the same thing.

Fixing This Problem

We recommend to have a plumber come in and fix / replace your shower valve or possibly, install a thermostatic mixing valve to help regulate the water pressure and keep the temperature steady for you while you shower.


If you have any questions about toilet leaks or other plumbing issues, call Atlantis Plumbing today at 770-505-8570. We are available 24 hours a day, 7 days a week.

We Offer Plumbing Services in Metro Atlanta and Surrounding Areas

Fulton County, Bartow County, Cobb County, Paulding County, Cherokee County, Gwinnett County, and Douglas County.

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