What is wrong with my electric shower…?

WinstonTown

Ok, sorry for the random post but my shower is being a pain. It’s an old Mira Sport with a mind of its own. If I turn the water to “high” on the shower, even turned to a cold temp on the dial, the water is scalding -then suddenly illuminates “low flow”. Turn the water to “medium” and the pressure is pathetic when it’s at the temp I want. Can someone please tell me what I am doing wrong!?!

FreeBear

Sounds like you might be suffering from low water pressure & flow. Had a similar problem with my old electric shower. Did look at fitting one of these - https://showerpowerbooster.co.uk/

In the end, the shower died, and it got replaced by a Triton T80 Thermostatic. Not cheap, but well worth it in my opinion (still thinking about add in one of the above pumps though).

grumbler

WinstonTown said:

 If I turn the water to “high” on the shower, even turned to a cold temp on the dial, the water is scalding -then suddenly illuminates “low flow”.

By 'cold temp' do you mean the middle setting out of three?

Turn the water to “medium” and the pressure is pathetic when it’s at the temp I want.

Did you try controlling the flow at the lowest power setting (= no heating)?

If in this case you can make the flow high enough and the shower is thermostatic then the pressure is fine and the problem is, possibly, with the thermostatic valve.

Rdwill

If its been going for a while, it sounds like it's on its last legs.

Mira offer, what I consider, a reasonable supply and fit deal

https://www.mirashowers.co.uk/support/installation/shower-replacement/?gclsrc=aw.ds,aw.ds&=&id=ps_adw_mir_google-ppc_2017&gclid=CjwKCAjwtKmaBhBMEiwAyINuwBPZXmBqMzTp4VXqBpvNHJeI2ZEH0fhL-O0FkPXzDLETy6mLGkR6SBoCx90QAvD_BwE

Which I would take them up on, I have a mira jump that the dials are a bit hit and miss, but I'm having the whole bathroom done instead.  :'(

I suspect the 'resistors' behind the dials are just wearing out on mine. It's been in there over 10 years and used daily. So it doesn't owe me anything.

Bendy_House

Hi Winston.

It does sound like a water flow/pressure issue, so it's worth confirming whether this is a 'general' issue in your house, or just internal to your shower.

Simple first test: remove the shower handset from the hose and try again. Sorted? If 'yes', then the handset holes are partially blocked and need cleaning. (I don't think your symptoms show it as this, tho', because your low pressure light comes on, which it wouldn't if the restriction was on the OUTLET of the shower. But, still try it!)

Next, a pan under your cold kitchen tap, turn it on FULL for 10 seconds, measure the number of litres, and 'times' it by 6 to get 'litres per minute'. Report back to us. Also describe how 'powerful' the flow appears - does it splash your pants, or is it anaemic and can even be stopped with yer thumb?

If the F&P are clearly fine, then it's almost certainly an issue with the shower itself (assuming no-one turned an isolator down...) A DIYable - tho' a bit awkward - check is the filter on the inlet. Look up how to access this. In-law's Mira had this issue at one point - just a weird build up of debris over time. Cleaned it out, and shortly after this the pressure was so great it blew the safety pressure bb out!

So - handset, kitchen flow test, and filter. You want to know if it's the unit or the supply, 'cos there's no point replacing the unit if it's the latter.

Leccy showers: you press an 'on' button, and an electric valve opens. The water flows and acts on a pressure switch. If the pressure is high enough, it activates this switch and turns on the power to the heating elements. If the pressure AIN'T high enough, the switch instead lights the 'low pressure' indicator, and the shower won't heat up.

The 'low/med/high' control turns on usually 2 elements - a low one, a med one, and both. With both, you can have a greater flow of the same-temp water = a better shower.

The other control is effectively a 'tap' - it adjusts the water FLOW. Two things to know about this; one is that the greater the flow, the cooler the water ('cos the fixed element can't heat the fast water as well). The other important thing to understand about this control is, the GREATER the flow (the more towards 'cold' you turn it), the LOWER the resulting water pressure inside the shower unit, so the more likely the 'low pressure' light is to come on. This is because the MORE you OPEN a tap, the LESS the water is being held back = 'pressurised'. (Pretty sure that's the way round - ie the 'tap' temp control comes AFTER the pressure switch.)

So, if you have a general 'low pressure' issue, OR the water flow is being restricted in another way (blocked filter, isolator turned partially off, or even another source - eg loo - pinching some of the water), then the fault will manifest itself more when you turn the shower's flow colder, ie faster/greater.

As you turn the temperature UP, you are 'closing' the tap flow, so the pressure BUILDS up behind it = pressure is 'ok'. BUT, a reduced flow like this could mean temp too hot - which is exactly what you are experiencing, WT.

You turn the selector to 'high' = both elements on (which will need a high water flow to work), but the water is scalding (so clearly NOT enough water flow). You do the right thing and turn the 'temp' control (which is a 'tap') towards 'cold' which should increase the flow and sort the issue, but this doesn't work either. First, even turned towards 'cold', with water flow now at 'max', there STILL isn't enough water flow. And, with the 'tap' now fully open, and nothing restricting the flow through the shower, the pressure actually drops SO far it shuts the shower off = indicator light.

Head, kitchen, filter

shiraz99

As mentioned above it sounds like it may be on it's last legs and about to give up the ghost completely. I don't find electric showers to last that long, I've replaced mine twice over the years, the last one probably lasted 8 years at most. I now have a Triton T80z which was a doddle to install myself.

macman

Just bear in mind that if you replace it with a higher rated unit, then you may need to uprate the circuit cable and protection.

FreeBear

macman said:

Just bear in mind that if you replace it with a higher rated unit, then you may need to uprate the circuit cable and protection.

At which point, it is no longer a "like for like" repair, so probably requires Part P paperwork and a qualified electrician.

Bendy_House

And if it's Winston's domestic pressure wot's at fault, then there's no point just swapping the shower unit.

WinstonTown

Thanks all for your replies! The pressure is fine, and the head is brand new, so I think it’s the shower unit itself. It looks pretty old so I imagine it’s on its way out! 😬

Bendy_House

Still worth trying that inlet filter. I bet it's full of carp.