Power shower, rapidly varying temperature

[redyellowgreenblue]

Hi

Just moved into a rented flat. It's got a power shower (no pump) and worked fine for a few weeks. It's now developed a consistently swinging temperature, going from way too cold to way too hot in a cycle of about

30 seconds.

I don't know where this problem could have come from, and assume it's an issue with the electronics of the shower, but is there anything I'm missing, or that could be easily fixed? It would be great to avoid hassling (and therefore being hassled) by my rental company.

TIA

[Mr Fixit]

power shower and no pump??? a power shower means it has a pump is it not just an electric shower

[redyellowgreenblue]

Oops. I guess it's an electric shower then.

[Guy King]

The message from [e-mail] contains these words:

Do you mean an electrically heated shower?

If so then the chances are the flow-rate is too low for the temperature selected. If this happens then the water gets too hot and the shower shuts down for a while. Detection is either by pressure or output temperature.

Check all causes of low flowrate. I'd start with the showerhead being scaled up as a first guess, then perhaps a service valve not fully opened. Or, if it's the sort with a manual tap beneath the unit just forgetting to fully open the tap each time can cause this - my MiL had dreadful trouble with our shower 'cos she couldn't read the small print on the tap (ALWAYS FULL OPEN THIS TAP) with her glasses off - the default state for showering.

[redyellowgreenblue]

Yes

Thanks for the advice. What confuses me is that the shower worked perfectly well for the first few days we moved in, but this is suddenly a constant problem. I think you're very likely correct about the flow rate being the problem, but as far as I can see we haven't made any changes to this.

What do you mean by the showerhead being "scaled up"? Does that mean it's designed to in some way reduce flow? It's certainly a pretty poor shower head. I don't think it can be any of the other things you mention, as we haven't meddled with anything like that.

[Bob Mannix]

It's possible there is an inlet filter and a piece of debris has got into it. Take the shower head off and run it with just the hose. If it exhibits the same symptoms, it will be some problem on the inlet (water pressure, blockage etc). If it doesn't, it's possible the shower head is too scaled up or something.

[Mr Fixit]

Scaled up refers to it being blocked by limescale as in the white stuff in your kettle

[Guy King]

The message from [e-mail] contains these words:

Clogged with limescale. Try unscrewing the handset completely and see if the temperature's stable then.

[John]

You will find the temperature is lower as you have removed a significant flow restriction. The holes block with limescale when the water dries off.

Remember - the temperature is a factor of:

1. The electrical power.
2. The rate of water flow over the elements. (Slow it down and it becomes hotter - too slow and it will trip off)

[DJC]

It may be a sign that the heater element is about to fail. A period of temperature instability can be a premonition of impending doom.

Electric showers last longer and scale up less if you turn down the temperature control and flush cold water through before turning the shower off.