Electric shower: Which type should I get?

Discussion in 'Plumbing and Central Heating' started by twodoctors, 25 May 2011.

  1. twodoctors

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    Hi all. Hopefully someone knowledgeable can help me.

    I have a condensation boiler, for a 4 bedroom house. The hotwater tank (about 3.5ft tall) is on the first floor and I have a large header tank on the top floor. I have a water pump for a "power shower" for my en-suite shower room. I have no idea how it is plumbed in, but connected to a electronic thermostatic control. That works just fine. I think we can about 15-20 minutes of shower with a full tank of hot water.

    The shower in the main bathroom however is next to useless. The water pressure for the hot water is non-existent, and the water is either very hot or very cold. So I thought I should get an electric shower for that room because if I add another pump for that shower there will not be enough water to go round when both shower are in use.

    I have had bad experience with electric shower, with very poor water flow. I have been looking at various "electric power shower" where there is a built-in pump. I am not sure which I should get however. Should I get one with main cold feed only (non-pump), header tank cold feed only or hot and cold feed one? The ones I have see are all under £300 mark, which I guess is ok. I have no wiring at present so I will need to arrange for an electrician to do that part, therefore power output isn't an issue.

    Thanks.

    Adrian
     
  2. stem

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    Power showers usually have dual impellers that pump stored hot, and stored cold water to a thermostatic shower mixer for blending. As the hot and cold pressures are then virtually the same, this gives a nice balanced supply to the shower.

    Pumps are available that can supply two showers simultaneously, or you could install a separate pump for the second shower. As you say though, the stored hot water will get used up more quickly. You will also need to make sure the cold header tank is large enough, as this would now be feeding hot (via the cylinder) & cold supplies to two showers.

    Alternatively, the other type of electric shower heats cold mains water as it passes through the unit. They are completely independent of the boiler and stored water system, but the flow rates are not so high. When selecting this type of shower, the higher the kW rating, the better the flow. Older versions were 7 or 8kW, but now 9 & 10kW versions are available which give a much better flow. If you are concerned that you will run out of stored hot water, then this may be a better solution.
     
  3. twodoctors

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    Thanks.

    How does one determine the pressure of the cold main without using special tools? I am torn between cold main electric shower and cold header-tank power shower. I don't think I should get the hot and cold ones as it might impact on the duration of my other power shower. Thanks

    Adrian
     
  4. stem

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    I'm a bit confused by your questions. Why do you want to determine the pressure of the main? With an instantaneous electric shower (the sort with the heater built in) the mains pressure has little to do with what comes out of the shower, because the flow is throttled down by the shower regulator to control the temperature.

    I don't understand what you mean by a "cold header-tank power shower" and a "hot and cold one" Power Showers pump both hot and cold water to a mixing valve. The cold water is from the same header tank that feeds the hot water cylinder as shown below. This gives a nice balanced pressure for both hot and cold supplies.

     
  5. twodoctors

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    Thanks for that. That changes things for me again.

    I have a power shower similar to your diagram, and I have always wondered where the cold feed comes from. If your diagram is correct then I have a problem.

    When I say electric power shower, I meant an electric shower with a built-in pump. I have seen types where it is fed from the cold feeder tank only, and types where it is fed from cold feeder tank and hot water cylinder. Both have built-in heating element, which I guess meant it uses less hot water.

    If I were to get one of those pumped electric shower, I fear I may run out of water in either the hot water cylinder or the header tank. I might just be better off getting a standard electric shower but a more powerful one. Please correct me if I am wrong.

    Adrian
     
  6. stem

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    Can't comment about one with a pump for hot and cold that has a built in electric heating element as well, never come across one, or even heard of one for that matter.

    If you're worried about running our of stored water, an instantaneous shower heating water from the cold main would be my choice.

    Having said that, you would have to go some to use a complete cylinder of hot water showering. I have a power shower, OK only the one, but we've had guests, five folks have showered one after the other, and it's not run out of hot water. Remember the boiler can replenish some of the heat whilst the shower is running and there is usually a few minutes gap between each shower for it to catch up a little bit more too.
     
  7. twodoctors

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    Thanks.

    My brother has a similar setup as mine. I think he has a smaller hotwater cylinder so by the time a third person uses the shower (or halfway through the second person) the water starts to run cold. It might be because his pump is too efficient. Or his boiler is useless. Or his water cylinder is a lot smaller (serves a 2 bedroom flat). I am just worried about the same thing happening to us, which defeats the purpose of having a decent second shower.

    Is the diagram you shown me a normal setup for a power shower? I think I ought to have a peep in the loft and see how the pump is plumbed. Also measure the size of the header tank.

    The hot + cold feed electric shower - http://www.plumbworld.co.uk/triton-as2000xt-thermostatic-1283-17658

    The header tank fed electric shower - http://www.plumbworld.co.uk/triton-tankfed-pumped-191-22861

    Adrian
     
  8. twodoctors

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    Arrr... it suddenly clicked. The hot-cold fed ones are pump only. No heating element in it.

    So back to my question. How does one decide whether I need a gravity fed electric shower or a normal decent electric shower? How likely am I to use up the water in the header tank and what would happen if I do?

    Thanks.

    Adrian
     

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