Electric shower from cold water tank

Postby Wooster » Thu Mar 05, 2009 9:23 pm


I have recently moved into a 3 bed house with a combi boiler but it still has a cold water tank in the loft feeding cold to the bathroom (mixer shower (over the bath taps) and a seperate electric shower). I would say it is not more than 50cm from the bottom of the tank to the top of the shower.

Mixer shower - hot is excellent, fast flow and warm but it overides the cold water completely so it is near impossible to get the right temperature consistantly enough to even wash your hair let alone take a shower. It's always too hot. Is this because of the uneven pressure?

The electric shower (Gainsborough Energy 1000x) is again fed off the cold water tank in the loft. The flow from the shower is very poor, the temperature is more or less consistant and warm but with the poor flow/pressure you have to hold the shower head up over your head, if it sits on the wall it just doesn't reach your body! I have estimated the flow rate of warm water through the shower at about 5 litres per minute by using a measuring jug and a stopwatch.

I suspect the way forward is either to get a new Electric shower, the highest possible kw rating or get a [b]pumped[/b] Electric shower but I don't fancy splashing out £200+ for a pumped shower unless it will certainly improve things.

Does anyone have any experience with pumped electric showers or could anyone suggest a way forward to getting a decent shower once in a while?

Any help or suggestions would be much appreciated

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Simply Build It

Postby Dave From Leeds » Fri Mar 06, 2009 11:33 am

One option might be to raise the cold water tank in the loft as high as it will go.
Dave From Leeds
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Postby rosebery » Fri Mar 06, 2009 12:05 pm

If you have a combi the tanks in the roof should have been removed. Do you still have a hot water cylinder as well? Are you quite certain that its a combi and not just a condensing boiler? That question might appear rude but its not meant to be - its attempting to get to the roots of your problem. What is the make / model of your boiler? That will help.

Your mixer shower doesn't work properly because the supplies are unbalanced. If you have a combi then the cold supply should also be mains pressure not from a tank.

Electric showers should be fed with mains cold water NOT tank fed. You may NOT pump mains so you either have to change it for a tank fed shower with a pump or give it some cold mains to run off. If the former you will now back in the same loop as your mixer shower ie unbalanced supplies.

Your system sounds like a bit of a lash-up but as you have bought the property there is no recourse to whoever did the plumbing. If he received payment for doing it then he should be hanged, drawn and quartered!

Simple solutions (on site unseen basis only) and assuming its a combi and that the combi has sufficent throughput to provide your hot water needs.

Bypass the cold tank (drain it first!) in the roof and repipe your cold mains feed going up into the roof to the bathroom(s). The simple way is just to connect the tank feed in the roof to the where the outlet of the tank goes back down. Thats not ideal configuration but it will work even on a temporary basis.

Your electric shower will now receive cold mains and should work much better.

Your mixer shower will work better than before but you really should consider exchanging the simple BSM for a thermostatic one.

Long term I suggest you need the services of a plumber to sort it all out for you.

Hope this helps.

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Postby Wooster » Fri Mar 06, 2009 2:35 pm

Thanks for your excellent response

The hot water tank has definitely been removed

It's definitely a combi boiler (Worcester 28cdi)

I understand your comments about running the electric shower off the mains but the flow around the house is not exactly excellent so I worry that that shower will not be brilliant and even with a thermostatic mixer shower, when the washing machine or wife turns on a tap, the shower will be interrupted.

So, in one way I can understand why the electric shower comes off the tank and was really hoping someone would be able to tell me that Pumped Electric Showers are 'excellent'. If you look at the description it appears that they are built just for this situation: Google "tlc-direct.co.uk/Main_Index/Showers_Index/Pumped_Showers/" but I'm not certain if its not just manufacturer's hype. I have called them and they suggest the flow rate through the pumped Triton averages 4 litres per minute but that is a pretty similar rate to what I am getting now (though it dribbles rather than rushes out!)

So, it almost boils down to, has anyone any experience with a pumped electric shower?

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Postby plumbbob » Fri Mar 06, 2009 5:53 pm

Fitting a pumped electric shower is not done to create a better shower, but is done simply because mains water pressure is not available and as Rosebery says, a normal shower such as the Gainsborough should be connected to the rising main and not a tank.

The flow from an electric shower is not dependent on pressure, but the capacity of the heating element. If the shower is set at full power, increasing the flow is only going to make the water colder. Gainsborough are budget models, so a new quality unit may improve matters, as would increasing the element size if your electrics can stand it.

No electric shower is ever going to perform as well as a mixer especially one connected to a combi.

Like Rosebery, I don't understand why the tanks have been left. That's just wrong.

If the water pressure is poor, instead of buying a new shower, why not put the money towards a new main? It would improve matters no end.
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Postby rosebery » Fri Mar 06, 2009 6:31 pm

The point is that the CWST SHOULD have been removed. Otherwise you have hot water at mains pressure (3 bar? ish) and cold at gravity pressure (0.25? bar ish).

That will still give you an unbalanced problem with your BSM. Your cold pressure around the house is currently low compared with the hot because if an iro 2.75 bar difference. That will not change if you keep the tank.

The shower you link to is designed for use where the mains pressure is exceptionally low and you run it off a tank. Personally I call that a power shower rather than an electric one. Electric showers are designed to be run off mains as I said before and you may not pump mains under Water Regs. Actually you can but you need specific authority from your water supplier to do so.

Sorry to labour the point but your solution to BOTH problems is get rid of the tank with a minor and cost effective (if slighty crude) piping change which is what the combi installer should have done in the first place!
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Postby Wooster » Sat Mar 07, 2009 7:31 am

Rosebury, thanks.

What you say makes sense and that's just I am going to do. A simple change for the electric shower in the first instance should soon see an improvement. I indeed to do this very soon and I'll let you know how it goes!

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