Why Does Flushing the Toilet Affect the Shower?

Why Does Flushing the Toilet Affect the Shower?
crawfordmech April 4, 2021

If you live in a busy household, you may have had the experience of getting a blast of hot water in the shower because another family member flushed the toilet while you were showering. While this doesn’t happen under ideal circumstances, it is a common issue in many American homes. Once you understand what causes the problem, you will be in a position to do something about it. Learn why and how it happens and some easy solutions to the problem:

Why Does it Happen?

If flushing the toilet in your home causes the water in the shower to get extremely hot, your plumbing is probably set up with a trunk and branch system. What this means is all the water travels through the trunk and then narrows to individual branches that are diverted to each room. When one room calls for water, it can divert some of the water already in use (the shower), to the secondary water use (the toilet tank). Because the toilet is calling for cold water, the shower then has to share the cold water it was using. This results in too little cold water in your mixture for the shower and a blast of hot water until the toilet tank is filled.

Prevention Tips

To avoid having blasts of hot water in the shower, check out these solutions in order from the simplest to the most complex:

  • Don’t flush the toilet when someone is in the shower. Depending on the cooperation between family members, this solution is often the easiest. It doesn’t cost a thing and eliminates the problem. However, even the most courteous family member can forget on occasion, so don’t be surprised if you still get an occasional blast of hot water while showering.
  • Reduce the amount of water in the toilet tank. This won’t stop the problem completely, but it will make the tank fill up quicker and make the incidence shorter. To do this, place a brick or a jug of water in the toilet tank. The downside is your toilet will not flush as well and may pose a problem with flushing wastes down the drain.
  • Slow down the refill rate to the toilet. You can do this by turning the shutoff valve below the toilet to the halfway position. This will cause the toilet to refill slowly and reduce the effect it has on the temperature of the shower. It may also cause noises as the tank refills.
  • Install a thermostatic mixing valve in the shower. This valve automatically adjusts the amount of hot and cold water to maintain the proper water temperature for the shower.
  • Change your plumbing. Your plumber can either widen the trunk or install a load balancing manifold to prevent issues with a blast of hot water in the shower when the toilet is flushed.

If you need help solving your plumbing issues in the greater Columbus areacontact us at Crawford Mechanical Services. We can assess your existing plumbing and offer solutions that will put an end to your hot shower woes.

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