Flow problem with electric shower

Ed Addis · May 25, 2018

My partner is unhappy with the flow from the 9.5kW Mira shower we have on our bathroom. We're considering upgrading to the 10.8kW one, although I'm in doubt that it will make much difference. At the moment we're not interested in any other solutions eg power shower, combi boiler etc etc. Reading around the subject, I'm puzzled that people frequently say that scaling up of the shower head is a problem for flow with an electric shower, because it seems to me that for a given mains water temperature, and shower water temperature setting, you will always get the same flow irrespective of shower head blockages. If I de-scale the shower head, so that the flow increases, surely the shower water temperature will drop, and if she turns it up, this will lower the flow rate again! Am I missing something here?

MJPD29 · May 25, 2018

Could be your water pressure

Midwest · May 25, 2018

You always be running around underneath an electric shower (even 10.8 one), trying to get wet.

telectrix · May 25, 2018

had a shower this morning. it was pi$$ing down. good for the garden though.

Pete999 · May 25, 2018

Ed Addis said:
My partner is unhappy with the flow from the 9.5kW Mira shower we have on our bathroom. We're considering upgrading to the 10.8kW one, although I'm in doubt that it will make much difference. At the moment we're not interested in any other solutions eg power shower, combi boiler etc etc. Reading around the subject, I'm puzzled that people frequently say that scaling up of the shower head is a problem for flow with an electric shower, because it seems to me that for a given mains water temperature, and shower water temperature setting, you will always get the same flow irrespective of shower head blockages. If I de-scale the shower head, so that the flow increases, surely the shower water temperature will drop, and if she turns it up, this will lower the flow rate again! Am I missing something here?

Descale the shower head.

Darkwood · May 25, 2018

You say your partner is unhappy with the flow rate, are you yourself happy with it and does she have asbestos skin and like it very hot?... against conventional showers an electric shower will give a reduced flow rate simply by the nature of their design and sometimes it's just how it is and not necessarily because there is any issue especially if this is a new install or girlfriend who may be used to a combi or tank fed shower.

Ed Addis · May 25, 2018

Hi, thanks for your reply. All I want to know really is whether scale in the shower head can reduce the flow for given inlet and delivery temperatures. I don't see why it should make any difference.

Darkwood · May 25, 2018

Scale will restrict flow and consequently increase temp' of water, if you are not already at full temp' (if its a dial setting type) then getting rid of scale will give better flow and you can raise the temp' setting to compensate for the increased flow, if you're already at full whack then how ever you increase flow you will proportionately decrease the water temp'.
Higher KW showers basically give faster flow rates at any given setting in comparison but it is not a matter of just upgrading your shower, the whole shower circuit is likely to require upgrade too subject to someone coming to access what you have existing.

If you are in a soft water area like I am then scale should not be an issue if you are unsure as to whether that is the problem.

I often find it is cheaper to change the girlfriend

mhar · May 25, 2018

Has the hose itself been changed? Some replacement hoses have a very small bore which can restrict the flow.

telectrix · May 25, 2018

talking about small bores.......

[ElectriciansForums.net] Flow problem with electric shower

Ed Addis · May 25, 2018

darkwood said:
Scale will restrict flow and consequently increase temp' of water ...

So if I turn down the water temperature to what it was before the scale, the flow will increase again to what it was! So what have I lost with the scale? That was the point of the original question.

darkwood said:
... getting rid of scale will give better flow and you can raise the temp' setting to compensate for the increased flow ...

But if I have the temperature set how I want it, with scale in the head, surely the flow will be the same as it would be if I set the same temperature without scale, because the temperature is determined by the flow rate, with or without scale?

Ed Addis · May 25, 2018

telectrix said:
talking about small bores.......

View attachment 42443

Yes - but is he going in for plumbing now?

Ed Addis · May 25, 2018

mhar said:
Has the hose itself been changed? Some replacement hoses have a very small bore which can restrict the flow.

Same point exactly - if the hose restricts the flow, the water temperature will be higher. If I turn the temperature down, I'll get the same flow as I would have with a larger hose, because the temperature is only determined by the flow rate.

Ed Addis · May 25, 2018

darkwood said:
I often find it is cheaper to change the girlfriend

Or settle for an unwashed one?

Ed Addis · May 25, 2018

Pete999 said:
Descale the shower head.

Please read the OP

Ed Addis · May 25, 2018

Matthewd29 said:
Could be your water pressure

The temperature is determined by the flow rate - if the water pressure was too low, it wouldn't be possible to get the temperature down to a usable level.

Wilko · May 25, 2018

Hi - my suggested process is - put the shower on the coldest setting it operates review the max flow rate you can get. If that flow rate is too low then perhaps it can be increased with descaling of the unit or the head. Once the cold shower rate is where it should be then you can review the flow rate at higher temp settings. If the flow rate drops significantly, the unit may need servicing. The kW difference you're looking at is not that great and both are powerful heaters when working correctly.

Wilko · May 25, 2018

Hi - my suggested process is - put the shower on the coldest setting it operates review the max flow rate you can get. If that flow rate is too low then perhaps it can be increased with descaling of the unit or the head. Once the cold shower rate is where it should be then you can review the flow rate at higher temp settings. If the flow rate drops significantly at the higher temp settings then the unit may need servicing. The kW difference you're looking at is not that great and both are powerful heaters when working correctly.

Midwest · May 25, 2018

Its an electric shower. The design is flawed. Either get a non electric version, have a bath (in front of the fire) or towel wash etc

telectrix · May 25, 2018

Ed Addis said:
The temperature is determined by the flow rate - if the water pressure was too low, it wouldn't be possible to get the temperature down to a usable level.

if the water pressure is too low,the heater will cut out giving you a cold shower. we have that problem. every time someone turns on a tap or flushes the bog, the shower goes cold.

PEG · May 27, 2018

Another little known and annoying fact,in a lot of areas,the water authority now employ a "pressure reduction" policy,between say 11.30pm and 5.30am,which affects operation of flow sensitive items.

It is popular in Australia,and reduces energy costs and leakage,during low use hours.

Expect the first three people you ask,at your water company,to be obstructive and non-committal

The problem arrives,when your device is set-up and functioning,by your plumber,during full service pressure...they seem reluctant to return during the hours mentioned,for a re-test

Ed Addis · May 27, 2018

Midwest said:
Its an electric shower. The design is flawed. Either get a non electric version, have a bath (in front of the fire) or towel wash etc

Thanks!

Ed Addis · May 27, 2018

PEG said:
Another little known and annoying fact,in a lot of areas,the water authority now employ a "pressure reduction" policy,between say 11.30pm and 5.30am,which affects operation of flow sensitive items.

It is popular in Australia,and reduces energy costs and leakage,during low use hours.

Expect the first three people you ask,at your water company,to be obstructive and non-committal

The problem arrives,when your device is set-up and functioning,by your plumber,during full service pressure...they seem reluctant to return during the hours mentioned,for a re-test

Our pressure is poor even at best. Fortunately we rarely use showers at the times you mention.

Ed Addis · May 27, 2018

Wilko said:
Once the cold shower rate is where it should be then you can review the flow rate at higher temp settings. If the flow rate drops significantly at the higher temp settings then the unit may need servicing.

Surely the flow will always drop significantly when the temperature is turned up? Temperature is entirely dependent on flow.

Octopus · May 27, 2018

Maybe ditch the electric shower and get a hot tank etc installed with a thermostatic head / pump installed - far better IMHO

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Octopus

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