Why does the heater turn off in the middle of the shower?


When the heater turns off in the middle of the shower, you get a tremendous surprise. Especially on cold days it is very unpleasant, and it is even more delicate when it happens with children or elderly people in the middle of winter, because they can catch a cold. The heater turns off in the middle of the shower for various reasons, which we will examine one by one in this article. Learn how to fix these issues here.

Oh! And before we forget. At the end of the article we have included a section of frequently asked questions about heaters. Do not miss it!

If the heater turns off in the middle of the shower, what are the causes?

Let’s first look at two tables, which as a summary will explain the causes and solutions for when the heater turns off mid-shower. The first table refers to gas heaters, and the second refers to electric ones. After these tables we will go into other details.

Why the gas heater goes out (table)

Gas supply failure.Check if the bottle is exhausted or if there has been a cut in the public gas service.
Insufficient gas pressure to keep heater running or achieve ignition.Check if the gas regulator is the correct one (depending on whether it is natural gas, butane or propane), or if there is any clogging in the gas installation.
Insufficient water pressure to keep the burner on.Increase the water flow by raising the tank, or install a pressurising pump.
Dirty exchanger (coil) with lime scale and other sediments.Clean the coil with bisulfite or some anti-limescale product.
The pilot (if any) goes out during use.The pilot is dirty or clogged and needs to be cleaned, or there is a problem with the thermocouple and needs to be cleaned or replaced.
The thermostat is faulty or poorly calibrated, and orders to turn off prematurely.Calibrate or replace the thermostat.

Links to acquire these spare parts through Suner


Why the electric heater goes out (table)

Failure in the power supply.Check if there has been a power outage.
There are problems in the installation that cause overheating and safety shutdown.Check the electrical installation to see if there is any false contact or short circuit.
The water pressure is not enough to keep the heater on.Increase the water pressure or install a pressurising pump.
The thermostat is faulty or poorly calibrated, and orders to turn off prematurely.Calibrate or replace the thermostat.
The power button of the electric heater is faulty and turns off by itself.Replace the power button.
The magnesium anode is worn out and no longer fulfils its function.Replace the magnesium anode.

Reasons why the heater turns off in the middle of a shower (more details)

It may seem simple, but one of the first things to check if the heater turns off in the middle of a shower is the batteries. Even if the initial start-up proceeded correctly, subsequent restarts may not occur if the auto-start batteries do not have sufficient charge. It is best to replace them.

Another frequent reason that causes the heaters to turn off during use is that limescale has accumulated inside the pipes of the hydraulic installation. Lime causes a drastic reduction in water flow, causing the heater to shut down (especially heater models that require a minimum flow or pressure to operate). Plumbers solve this by connecting a pump that circulates an anti-limescale product inside the installation.

If the heater is tight and has a forced draft, the gas outlet must work well, because if it becomes blocked or clogged (including the turbine), the smoke and excess temperature sensors will trip and cause a safety lockout. For this reason, the smoke outlet must be kept clean and the turbine lubricated.

Heater FAQs

We have already answered the question in detail “why the heater turns off in the middle of a shower”. But let’s look at some more general details. As we said at the beginning, there are so many frequently asked questions about breakdowns and problems with heaters that today we are going to dedicate a whole heading to answer several of them. We will do it as concisely as possible. On your marks… Set… Here we go!

Why does my step heater shut off when I turn on the cold water?

Perhaps you are one of those who have frequently had to ask themselves: Why does my step heater turn off when I turn on the cold water? It seems like a bit of mysterious behavior on the part of the heater, but it’s actually not that weird.

The first thing to say is that some heaters do not allow the combination of hot and cold water taps at the time of use, and in this case, they are turned off as a safety measure. But in cases where the heater does accept this mixture but turns off when you combine the hot with the cold, what may be happening is that, when you open two taps at the same time, the water flow drops below the minimum you need. This affects the heater, which then turns off.


Something else that we suggest regarding this point is that lowering the temperature of the water at the time of use (after the heater has already used the fuel or energy to heat it), is not an optimal method. In fact, it reduces the efficiency of the equipment, from the point of view of the new eco-design regulations. The best thing would be to manage the temperature of the water in the heater itself, and from there choose the temperature at which it will be used in the taps, or almost.

Why does the water heater pilot light go out?

If the question is why does the water heater pilot light go out, that is, when it is a non-instantaneous design heater, the first thing to check is if the gas supply has been interrupted.

The gas supply can be interrupted not only when the fuel in the cylinder runs out, or if there is a cut in the public service. Something that often happens is that the gas regulator is not the right one for your type of gas, and then it can interrupt the supply at times. There are regulators that adapt to various types of gas, but if this is not the case, it is best to use the gas regulator that corresponds to each type of gas, be it natural gas or liquefied petroleum gas (butane and propane). Each one needs a regulator specially calibrated for the pressure with which the gas is bottled. Otherwise, it doesn’t work well.

Another problem that causes your water heater pilot to go out is the pilot itself, which can be dirty or clogged, and by not allowing gas to flow through it, then it goes out. The solution may be to clean the pilot without having to disassemble it (if it is not too dirty), or if it is very dirty, disassemble it and clean it thoroughly. If it is damaged, it is better to replace it.

But since the pilot in this type of equipment often goes together with the thermocouple (that is, the flame and temperature sensor), what may be dirty or damaged is the thermocouple, and that will affect the pilot. The thermocouple sensor can be cleaned, and the part will work perfectly again. However, if this is not the case and the problem persists, it will be advisable to replace the thermocouple with a new one, whether or not it has the pilot included.

Click here to access the thermocouples for sale at Suner


Why doesn’t the water heater turn off?

On the other hand, if what happens to you is that the water heater does not turn off automatically when the demand for water ceases, then what may be happening is that there is a fault in the instantaneous shutdown mechanism or an excess of water flow which causes a continuous increase in pressure, which sends the heater misleading information that a tap is kept open.

The fault in the ignition mechanism may be due, for example, to the ignition membrane being hardened and keeping the ignition rod pressed, or to the microswitch being stuck or damaged, and remaining in the ignition position even though there is no demand for ignition. It is best to give all ignition components a good cleaning and lubrication maintenance, or even replace them with spare parts.

The other problem that we pointed out above is that, when the hydraulic system of the house has a lot of flow, this can cause excess pressure. Excess pressure causes the flow heater to operate as if there is a demand for water when there is not. To reduce the water pressure, a pressurizing pump can be installed. This small but effective piece of equipment helps to set the pressure level exactly where it is needed, be it reducing or increasing it.

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