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Is Toilet Connected To Water Heater (Everything You Need To Know!)

Most activities in the toilet require lots of water for cleaning and flushing off solid waste. During the cold weather, one may need hot water to clean and flush the toilet, necessitating a water heater connected to the toilet water system.

But is toilet connected to water heater? Yes. A toilet can be connected to a water heater to supply hot water for flushing, hand washing or any other activity requiring hot water. However, using a water heater requires particular water pipe installation to avoid overheating and pipe bursting risks.

This guide provides a detailed outlook of a water heater system in the toilet and how hot water improves bathroom conditions. In addition, we shall discuss the benefits and dangers of using hot water in the toilet.

Is Toilet Connected To Water Heater?

Yes. Some toilets are connected to water heaters to warm water, especially during the cold season. Using heated water raises the room temperature and removes tough stains in the toilet bowl.

Most toilets have a cold and hot water connection system controlled by a gate valve to open and close either method. A green pipe with white markings marks the hot water system.

The supply pipe is directly connected to the toilet water reservoir from the water heater in the house. This line stays open, but the water flow is regulated by a valve and a floating ball in the fill tank to prevent overflowing.

Accordingly, toilets are connected to water heaters using piping systems that deliver the hot water into the toilet tank for flushing solid waste to the sewer line.

Some hot water is directed to the hand-washing sink for other cleaning activities. If your toilet is not connected to the water heater, read the next section on connecting the hot water heating system.

is toilet connected to water heater

How Does Hot Water Get Connected To The Toilet?

Most modern toilets are designed with an elaborate water system consisting of separate cold and hot water systems.

  1. For old toilet designs with cold-water systems, one has to install a hot water system separately with the capacity to withstand high temperatures and pressure.
  2. You need to install a hot water pipe system to connect the hot water to the toilet. According to the ANSI/ASME A13.1 2007 standard color chart for hot water pipes, the color code is green with white lettering for supply and return.
  3. The green pipe delivers hot water from the water heater to a valve below the toilet reservoir tank.
  4. From the valve, the water passes through a tube to the toilet tank until it reaches the top, and the valve closes before it overflows.

This is how the hot water can get connected to the toilet in average designs.

What Is The Standard Toilet Water Temperature?

  • According to the 2018 International Plumbing Code, the standard water temperature in a toilet should range between 34 and 37 degrees Celsius.
  • Water temperature should be slightly below body temperature to avoid risks of burning.
  • You can regulate the water temperature at the gauge valve to suit your desired temperature.
  • Avoid too much hot water as it might damage the brittle piping system causing leakages and bursts.
  • To maintain proper water temperature, you need to check on the pressure gauge and maintain a standard level.
  • Consider the capacity of the water lines to withstand pressure and high pressure to avoid bursting and leakages.

Effect Of Using Hot Water In The Toilet

Most toilets use cold water to clean and flush the solid waste in the bathroom. However, some homes have their toilet water supply line connected to a water heater during the cold seasons to warm the water.

Hot water in the toilet has merits and demerits, as shown below.

Advantages Of Hot Water In The Toilet

  • It provides efficient toilet flushes
  • Keeps the toilet bowl clean
  • Kills bacteria and germs in the toilet
  • It helps eliminate bad odor
  • Ensure a supply of warm water for other activities, such as handwashing

Disadvantages Of Hot Water In The Toilet

  • Boiling water can damage the water line systems
  • Scum and minerals from boiling water clog the water pipes
  • Boiling water may spill from the toilet reservoir and cause slippage and fall
  • The use of hot water is less economical

How Do You Fix An Overheating Toilet Even After Flushing?

Once you flush your toilet with hot water, it should take 3-5 minutes to cool down to average temperatures. However, this is not always the case. Sometimes the toilet bowl remains abnormally hot for long hours, making it uncomfortable to sit on.

If you experience such a situation, check for the following issues.

  • Check the water level in the toilet tank. If the water level is too high, it can cause the water to boil continuously, causing the whole system to heat up
  • Ensure the water level in the reservoir is standard by adjusting the floating gauge ball to close the valve at the correct position
  • Check the cold and hot water connection systems. Ensure no cross-connection would cause a mix-up of the hot and cold water
  • You should also adjust the thermostat to a desired temperature within the set standards to avoid overheating
  • Inspect the pressure gauge to avoid too much or low water pressure, as it affects the water temperature directly

If you inspect and fix all these possible causes, but your toilet still heats up, consider having a plumber check the entire toilet system. It might be a faulty part or a malfunction of the toilet components.


Here are the frequently asked questions about using hot water in toilets.

Q: Do Toilets Need To Have Hot Water Systems?

No. It’s not a must for toilets to have hot water. The primary function of water is to flush solid waste and do any other necessary cleaning activity in the bathroom.

Cold water or water at room temperature can equally serve the purpose. Therefore, you don’t have to use hot water in your toilet. Hot water is a luxury to be enjoyed at a cost.

Q: Can Boiling Water Damage Or Crack My Toilet?

No. Boiling water cannot damage your toilet. However, boiling should not be poured or flushed into the bathroom as it damages the pipe connections and other rubber appliances.

Boiling water will cause the pipes and valves to expand and become loose, causing leakages and spills. Brittle pipes will crack and burst under pressure and high temperatures.

Q: What Causes Hot Water To Come Out Through The Cold-Water Pipe?

The leading cause would be a cross-connection in the piping system leading to hot and cold water mix-up. Check the regulating valves and the connection from the main water supply for malfunctions.

You can consult a plumber if you need help finding your way through it.


You can connect your toilet system to a water heater to supply hot water when needed. Hot water is essential in maintaining the room temperature during cold seasons and ensuring a cleaner toilet.

With the proper connection, hot water helps kill bacteria and germs in the toilet that would have otherwise survived in cold water. However, not all toilets are connected with water heaters since the existing water supply lines cannot withstand high temperatures.