Electric Shower Going Hot And Cold? (here’s why & what to do)

At some point or other, we’ve all had that blast of cold water whilst enjoying a hot shower. Whatever else it does, it certainly wakes you up! If you want to know what causes it and more importantly how to fix it, keep reading.

The main reason for an electric shower fluctuating between hot and cold is almost always down to water pressure.

Why Is My Electric Shower Going Hot And Cold?

Many of us rely on our electric shower, they’re incredibly popular and generally work really well. But, every now and then, we hear of problems concerning the electric shower not maintaining the correct temperature. Or more particularly, going hot and cold.

As we said earlier this is almost always down to not enough water running through the shower. Now, there can be a number of reasons for this which we’ll get into in a minute. But first, we need to remind you about safety.

Electricity and water don’t mix and you should never tamper with anything electrical unless you are confident and competent in your abilities. If you have any doubts, we advise you to contact an electrician or a plumber.

Water Pressure

The water pressure that enters your home needs to be a minimum of one bar of pressure for an electric shower to operate effectively. Coincidentally, local water authorities guarantee water pressure of at least one bar of pressure. One bar of pressure is the amount of pressure which is needed to raise water to a height of ten metres.

To check your water pressure, time how long it takes to fill a one litre jug using your shower head. If it takes six seconds or less, then the water pressure is fine. If it takes more than six seconds, you could have low water pressure.

But before you contact the water authority, run the same test from other taps in your home. The chances are, that the problem is the actual shower itself and not the whole home.

Stopcock

The first place to start is the actual stopcock which supplies water to your shower. Check that it is fully open as it can only supply water at full pressure if the valve is fully open.

Shower Head

Showerhead

Remove the shower head and inspect it. Check to see if it is clogged or even partially blocked. The usual culprit here is limescale which could be blocking the small holes of the shower head. You can clear these using a cocktail stick or small needle inserted into each of the holes.

Shower Hose

Sometimes the actual shower hose itself can become twisted or damaged. If it is twisted, that would restrict the flow of water and if it is damaged this could also be the reason the pressure isn’t high enough. Shower hoses are usually constructed in two layers, an inner rubber or plastic hose encased in a steel hose. 

It’s usually the inner hose which can be problematic, either twisted internally or leaking. Sometimes just replacing the shower hose could solve the fluctuating temperature problem.

Shower Inlet Filter

To inspect the inlet filter on the shower usually involves taking the shower apart and is probably best left to an expert.

Water Being Used Elsewhere

In some cases, if someone turns on the cold tap elsewhere in the house, like the kitchen sink, or flushing the toilet, it can reduce the water pressure in the electric shower.

Limescale

Another reason the water pressure could be too low in your shower, which can cause it to run hot then cold, is limescale. With more than 60% of the UK and around 85% of the US living in areas of hard water, limescale will eventually build up in your water pipes.

It is a build up of mineral deposits found naturally in the water which settle in the pipes, coating them with the forerunner to rock. You can buy proprietary limescale removers which can be used to soak the shower head and shower hose. However, the internal components of the shower can also become affected by limescale deposits.

If the shower head and shower hose are not the issue, and your home’s water pressure is fine, it is most likely to be the internal components of your shower which are at fault. 

It is possible to replace individual components (we would recommend calling a plumber or electrician) or you might need to replace the whole shower unit.

Electrical Faults

Shower

There are a number of electrical faults which could cause the temperature to fluctuate in the shower. It could be any of the following;

  • Faulty Heating Element
    Electric showers heat cold water as it runs through the shower via an internal heater tank. The heating element inside the water tank in the shower can develop a fault which stops the water from heating.
  • Faulty Thermal Cut Off (TCO) Switch
    The thermal cut off switch cuts in if the water in the tank becomes too hot. Once the water in the tank cools enough the TCO shuts down and allows the water heater to start up again. If the TCO is faulty it could cut in even when the water is not too hot.
  • Faulty Flow Valve
    The water flow into your electric shower is controlled by a flow valve. If this develops a fault ti will probably need to be replaced.

We advise you to contact an electrician and/or a plumber if you suspect any of these faults.

Remember, there are a number of reasons why your electric shower goes from hot to cold, and the best person to diagnose what’s causing the problem is either an electrician or a plumber.

For more information on why your electric shower is running cold, follow this link.

Frequently Asked Questions

Why does my shower get cold then hot again?

If your shower gets cold and then hot again, it’s most likely to be caused because another tap is being used elsewhere in your home. For example someone turns on the tap in the kitchen or flushes the toilet. 

Why does my electric shower go cold after 2 minutes?

If your electric shower goes cold after a short time it is probably a faulty thermal cut off switch. The thermal cut off switch is designed to prevent the water in the shower from overheating. If it detects that the water has become too hot, it shuts the heater off until the water reaches a safer level, it then allows the heater to start up again. If it has developed a fault, this could cause your shower to go cold after a short time period.

Why is my electric shower only hot for a few minutes?

If your electric shower goes cold after a few minutes it’s probably caused by a faulty Thermal Cut Off (TCO) switch. If the water in the internal tank of the shower becomes too hot the TCO shuts the power to the heater until the water cools enough. At which point the TCO allows the heater to start up again. If the TCO is faulty it would explain why your electric shower is only hot for a few minutes.

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