Why is my shower cutting out all the time?

Question

Is my shower cutting out because of water pressure in the house? It seems to happen more frequently when someone else uses a tap or flushes the toilet, which makes me think it could be that rather than a fault with the shower unit. But it even happens when I'm the only one in the house. This isn't even an old unit, installed around a year ago (mira)

William · Accepted Answer

Usually low water pressure, but if it has been happening before you may have to replace thermal cutout switch.

Teodor · Answer

If it’s happening more often when someone flushes the toilet or uses a tap, that does point towards a pressure/flow issue rather than the shower itself. Electric showers (like Mira) have a minimum flow rate and pressure requirement, and if the supply drops suddenly they can cut out or cycle hot/cold to protect the heating element.
However, if it’s also happening when no other water is being used, it could be:
Low incoming mains pressure or restricted flow (partially closed stop tap, faulty pressure reducing valve, blockage in pipework).
A clogged inlet filter inside the shower.
A thermal cut-out activating due to overheating.
An electrical issue (loose connection or undersized circuit).
I’d suggest checking that the main stop tap is fully open and asking your water supplier about your mains pressure. If that’s fine, a qualified electrician/plumber should inspect the shower unit, inlet filter and supply to rule out a fault with the unit or installation.

Sean · Answer

Yes this is based on the element either overheating or a difference in load being pulled is making the RCD trip.

Both are a result of pressure change or low pressure meaning the pump or element are over working.

Long term result of this is that the shower could burn out.

Damon · Answer

Yes — it could be related to water pressure/flow, but your symptoms suggest it’s more likely a flow restriction or the shower’s thermal cut-out activating, rather than just general house pressure.

When someone uses a tap or flushes the toilet, the incoming cold water flow to the shower drops. Electric showers (like Mira) rely on a minimum flow rate to keep the heating element cool. If the flow drops too low, the water overheats and the unit automatically cuts out to protect itself. That explains why it happens more often when other outlets are used.

However, the fact it also happens when you’re the only one using water points to an underlying issue. The most common causes are:

Limescale buildup in the shower head or hose, restricting flow
Blocked inlet filter inside the shower unit
Low overall flow rate to the shower (e.g. partially closed stop tap or undersized pipework)
Less commonly, a fault within the shower (e.g. thermal cut-out or flow switch issue)

The most likely scenario is that your flow rate is borderline, and any small restriction (like scale) is tipping it over the limit, causing the shower to overheat and shut off.

As a quick check, remove the shower head and run the shower. If it stops cutting out, the issue is almost certainly flow restriction from the head or hose. Also try running it on a lower heat setting — if that resolves it, it further confirms a flow-related issue.

If basic checks don’t fix it, the next step would be to inspect the inlet filter or have the unit checked, as it may be partially blocked or starting to develop a fault.

Alex · Answer

does sound like it could be related to pressure/flow, but with an electric shower (like most Mira units), it’s often more about flow rate and overheating protection than just household water pressure.

Electric showers have a safety feature that cuts the power if the water flow drops too low or the unit starts to overheat. When someone flushes a toilet or runs a tap, the flow to the shower can dip briefly — that can trigger the cut-out. That part of what you’re seeing is fairly normal if the system isn’t well balanced.

However, the fact it’s also happening when no one else is using water suggests something else may be going on, such as:

Partially blocked inlet filter (very common, especially within a year if there’s debris in the pipes)
Low incoming mains pressure/flow overall
Thermal cut-out activating due to scale build-up or a developing fault
Faulty solenoid valve or internal component in the unit

A few things you can check yourself:

Make sure the shower head and hose aren’t scaled up or blocked
Check if the flow from the shower seems weaker than it used to
Clean the inlet filter (usually where the water pipe connects to the unit — isolate water first)

If none of that helps, it’s probably worth getting it looked at under warranty — a 1-year-old Mira shower shouldn’t be cutting out regularly unless something’s wrong.

In short: pressure drops from other taps can contribute, but it shouldn’t be happening all the time, so I’d lean toward a flow restriction or internal fault rather than just normal pressure variation.

Chris · Answer

You need to do some maths. Find out kW of the shower if its 8.5kw. Eg. 8500 ÷ 230 = 36.9amp. Make sure your mcb is now lower than 37 amp mcb

Kelsey · Answer

Hi. It can be a combination of things ie water flow rates and shower specs.

Russell · Answer

What model? if it is a mira sport 7.5kw it is likely either fitted incorrectly or faulty, check your water pressure  via a cold tap if it is flowing nicely in the sink where bathroom contains shower, pressure is likely no issue,  the >7.5kw  showers are  usually a more modern or older version these can have the same condition as stated above. Kind regards RTS

Harry · Answer

1. Low water pressure / flow
•	If the flow drops too low, the shower overheats
•	The thermal cut-out trips
•	Shower goes cold or shuts off
•	Comes back after 30–90 seconds once it cools

Common reasons flow is low:
•	Blocked shower head (limescale is a big culprit)
•	Partially closed isolation valve
•	Old or kinked pipework
•	Mains pressure issues (worse at peak times)

👉 Try running the shower with the head removed.
If it stays on = blocked head.

2. Overheating (even with decent pressure)
•	Electric showers are basically tiny kettles.
•	Things that push them over the edge:
•	Shower set too hot
•	Summer mains water already warm
•	Long runs on full heat
Fix:
Turn the temperature down slightly and increase flow.
Hotter better if it keeps cutting out.

3. Electrical supply issue
Less common, but serious if this is it.
Possibilities:
•	Loose connection in the isolator
•	Failing pull cord switch
•	Cable overheating
•	RCD/RCBO nuisance tripping
•	Shower goes completely dead
•	Needs isolator flicked off/on
If it’s electrical, don’t ignore it.

4. Faulty thermal cut-out or heating element
•	Pressure is good
•	Shower head is clean
•	Still cuts out randomly

Then the shower unit itself may just be on its way out.

Lee · Answer

Cutting out or tripping the electricity?

If it's tripping the electric there's a fault.  
If it's going cold then it could also be a fault.  
If it stays warm on a lower setting it's water pressure.

Why is my shower cutting out all the time?

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