What Does Flushing the Toilet While Showering Do

Jump to Section

If you're enjoying a relaxing shower, you suddenly get blasted with hot or cold water! Does your relaxation end there? Well, being blasted with scalding hot water can be a painful shock, especially if you're not expecting it. But that's exactly what happens when other members of your household flush the toilet when you're showering.

When someone flushes the toilet when you're showering, the toilet needs water to refill the tank. Toilets use cold water, so it pulls the cold water from your shower, increasing the hot water. While the toilet uses this water to refill the toilet tank, it also causes a drop in water pressure in the shower.

Dealing with this problem can be a real hassle, especially if you live in a large household. Let's learn why and how it happens and some preventive measures you can take to avoid such.

How Does Flushing the Toilet Affect the Shower?

When you flush your toilet, it affects the water pressure in your pipes, heating your shower. This usually happens because of your plumbing setup, which is a trunk and branch system. The water runs from one side of the building to the other in a large pipe, with small offshoot pipes that connect to different plumbing fixtures like your shower, washer, toilet, or sink.

How Does Flushing the Toilet Affect the Shower?
Image credit: https://bathroomworld.ne

If you have lower water pressure in your home, then when one fixture takes some of that water from the trunk pipe, there is less water for the rest of the fixtures. Sometimes, homes have just one water supply line for a shower, tub, and toilet in the same bathroom.

So, when flushing the toilet, it needs water to fill the tank. The toilet gets water from the trunk pipe, and the shower or tub gets water from the same place. When you flush the toilet, though, less water flows to the shower, and if your water pressure is too low, it will not generate enough flow through that one pipe to fill your bathtub or shower.

How to Prevent Flushing the Toilet from Affecting Your Shower

Although a flushing toilet affecting your shower is a common occurrence, that doesn't make it unbearable. Here are some of the tips for preventing a toilet flush from running your shower:

Install a Thermostatic Mixing Valve Monitors

You can install a thermostatic mixing valve monitor to help balance your hot and cold water. Thermostatic mixing valves automatically adjust the amount of hot and cold water to maintain a safe but comfortable water temperature for the shower.

Install a Thermostatic Mixing Valve Monitors
Image credit: https://static.cms.yp.ca/

If the cold water flow is reduced due to a toilet flush, the valve automatically adjusts the amount of hot water being mixed. This keeps the shower temperature more consistent, even when other plumbing fixtures are using water.

Adjust the Toilet Supply Valve

If you have a toilet with an old-style ballcock valve, you can adjust the water level in the tank to help prevent flushing from affecting your shower. The ballcock is the float-operated device that controls how much water flows into the tank. Make sure you know how to replace the toilet valve if it can’t be adjusted.

Adjust the Toilet Supply Valve
Image credit: https://www.thespruce.com/

To raise the water level, turn the adjustment screw clockwise. To lower it, turn it counterclockwise. To test your adjustments, flush the toilet while you're taking a shower and listen for any changes in water temperature or flow.

Don't Flush the Toilet When Someone is in the shower

This is a no-brainer tip. Why would you flush the toilet when someone is in the shower, yet you know the consequences? Depending on cooperation between your family members, this is one of the easiest solutions to this issue. If you have a separate bathroom, try to encourage other family members not to flush the toilet when someone is in the shower.

You can also place a sign on the door as a reminder. If you don't have another bathroom, it might be worth investing in a low-flow toilet that uses less water for each flush or a dual flush toilet that has a low-flush option for liquid waste. Also, note that even that courteous family can forget on occasion, so don't get surprised if you still get an occasional blast of hot water while showering.

Install a Load Balancing Manifold

If you have a multi-head shower, you can install a load balancing manifold. This will help ensure that each head gets the same amount of water pressure, which can help prevent scalding. This device replaces your trunk and branch system with individual lines for each toilet, shower, and washing machine.

The manifold connects directly to your water heater and supplies each fixture with its own dedicated hot water line. It also connects directly to the main water supply for cold water. Now, when someone flushes the toilet, your toilet doesn't need to borrow water from your shower because it has its very own supply. You'll need a professional plumber to install the manifold system.

Reduce the Amount of Water in the Toilet Tank

If your toilet is old, it may use a lot of water with each flush. You can reduce the amount of water used by installing a new, low-flow toilet or adjusting the fill valve to lower the amount of water in the tank. You can also save water by making sure that you only run the shower while you are in it.

You can also place a brick or a jug of water in the toilet tank. The brick will take up the space in your tank, so there's less room for the water to go. On the downside, you'll still experience a temperature change and pressure drop, although it won't last long. However, it can also result in a weak flush, leading to an eventual overflowing toilet. You can also reduce the amount of water by switching to a low flow toilet.

Change the Plumbing

If you still have some water in your tank after you flush, it could be because the fill valve cannot keep up with the amount of water necessary for a full flush. In this case, consider replacing or repairing the valve or purchasing an entirely new toilet. Look for some of the best flushing toilets on the market to find one that will suit your needs.

FAQs on What Flushing the Toilet Does While Showering

Why does flushing the toilet make the shower hot?

When someone flushes the water when you're showering, the toilet needs water to refill its tank. When this happens, the branch going to the toilet doesn't have enough water since you're showering. Your toilet, therefore, needs to pull some of the water it needs from the shower.

As the tank fills with cold water, it leaves you with cold water in the shower. This can be very uncomfortable if you are trying to relax and unwind in a hot bath or shower.

Why does flushing the toilet affect the shower?

There are a few different reasons why flushing the toilet can make the shower hot. One of the main causes is that when you flush the toilet, there is less water available for the shower due to the fact that water is being pulled from it to refill the tank in the toilet.

What does flushing the toilet do to the shower?

There are a few different things that can happen when you flush the toilet while showering. Some of these include reducing the temperature of the water in your shower by drawing water from it to refill the tank or causing changes in pressure that can lead to colder water coming through the tap.

Final Thought on What Flushing the Toilet Does While Showering

It can be awkward when the toilet flushes when you're showering. However, it's important to know what flushing the toilet does to your shower so that you can be prepared for it. If the toilet flushes on its own when showering, make sure you rectify the problem before it becomes severe. If it's out of your hand, make sure you reach out to a professional plumber to help you out.


Ryan Copley

Ryan Copley

Having spent years participating in bathroom, kitchen, and home renovations, Ryan uses this experience to write informative blog posts on a wide variety of home renovation and kitchen topics.

Related Articles

Download Free Chart Now!

Your email will be used only to confirm your request and to provide free kitchen information. By submitting your info on this form, you are agreeing to be contacted regarding your service request by means of email. This is no obligation form and doesn’t require you to purchase any service.