Electric shower for cold mains low pressure

Discussion in 'Plumbers' Talk' started by Bisset2297, May 20, 2022.

  1. Bisset2297

    Bisset2297 New Member


    Just looking for a bit of advice here.

    I have a cold water tank in my loft and a hot water cylinder in my cupboard and the boiler is downstairs - I believe this is called a gravity fed system?

    My electric shower is fed from the cold mains supply, the bathroom is upstairs and I live at the top of the hill in my housing estate.

    The shower I had previously was the triton cara 8.5kw which worked okay for a good few years (maybe 6?) until recently it started to go from extremely hot to freezing cold to the point I couldn’t use the shower at all.

    I bought the new triton easy fit 8.5kw thermostatic shower, plumber came by to fit it which he did, but then told me my water pressure is too low and that the low pressure light is on which it shouldn’t be so I was to call the water board. The shower takes ages to heat and even when it does it fluctuates and drops to cold. He wasn’t very helpful and couldn’t get out the door quick enough after I gave him his £80.

    anyway, got the water board out who tested the pressure which was between 1.2 and 1.4 bar pressure into the house which he says is adequate. He told me by the time the water goes 14ft up to the shower, it will drop in pressure. So really, the pressure at the point of the shower will be lower than 1.2 bar so how that is adequate I do not know especially if I can’t get use of my shower.

    I couldn’t tell you what the actual pressure is at the point of the shower, don’t know how I would measure this or if it would need to be a plumber but the triton says it works with minimum 1bar and it’s not, so I’m thinking it’s not 1bar by the time it reaches the shower.

    I’m stuck now on what to do.

    I’ve been looking at showers that operate with minimum bar pressures of 0.7 in the hopes that it would actually heat up? Would this do the trick?

    I’ve no idea what the cable size is, I’ve looked to see if there are markings on the cable but no such luck. I’ve no idea what the kw was for the shower before my Triton Cara, but if the Cara was working okay for a few years then can I assume that the cable size was adequate for the 8.5kw?

    the water board told me to maybe look at a 7 or 7.5kw to see if that would help but I didn’t think the kw controlled the heating element? I thought in order for the electric shower to produce hot water, there had to be enough water pressure?

    can someone shed some professional light as I’m definitely no plumber or electrician!

  2. AnotherTopJob

    AnotherTopJob Screwfix Select

    Even if you get an electric shower that works on your pressure, flow won't be great.
    Have you considered a power shower or adding a pump?
  3. Bisset2297

    Bisset2297 New Member

    I thought power showers were only to be connected to the water tank? Mines is currently mains fed and have been told I shouldn’t connect a pump to the mains?
  4. Tilt

    Tilt Screwfix Select

    But you said you have a tank and cylinder, so not a bad option.

    I have a very similar set up to yours and a Mira Event power shower was fitted.
    I never like the noise so have the power left off but still get a lovely shower from the gravity system.

    Is there a reason you chose an Electric shower over other types???

    We have lots of electric showers at work / student accommodation and if the temp is good then the flow is never great. Mostly 8.5Kw.
  5. Bisset2297

    Bisset2297 New Member

    Yeah but just not sure how much it would cost be to get it fed from the water tank instead?
    I’ve always had an electric shower, not really known any different
  6. AnotherTopJob

    AnotherTopJob Screwfix Select

  7. Bisset2297

    Bisset2297 New Member

    Thanks, I’ve been looking at other showers but I’m not sure if my cable size would hold a 9kw? I’ve also been told that it could be a blockage somewhere in the pipes to my shower as I said all my bathroom taps are normal & there’s no change so was advised there’s maybe a blockage?
  8. BiancoTheGiraffe

    BiancoTheGiraffe Screwfix Select

    There are booster pumps available for the mains, but I don't know how they are viewed by the suppliers... As far as I know, most won't allow you to pump from the mains...
  9. Bisset2297

    Bisset2297 New Member

    My neighbour has one, said it’s great but then the water board said that a no go, does the pump need to be connected to the cold and hot water or can it just be connected to the cold mains?
  10. BiancoTheGiraffe

    BiancoTheGiraffe Screwfix Select

    I'd have a look at the regs on pumping from the mains, there's a lot of them on the market... Can't believe they'd be so readily available if they were blanket banned.

    As I understand, you should feed a shower both hot and cold by the same method (twin pump from stored water, cold mains/hot from unvented cylinder, or gravity fed hot/cold.
  11. Nexial

    Nexial Active Member

    Anybody is free to pump from the mains, as long as you do not attempt to pull more that 12 litres per minute (the same as the average mixer shower uses)
    As a rule the water company only need to provide 10 Litres per minute and 1.0 Bar of pressure and flow to your boundary stoptap.

    As an earlier poster said, your best option would be to fit a gravity shower / powershower (essentially a gravity shower with pump)

    This would be piped from your cold water storage tank in the loft and from your hot water cylinder, so putting a pump onto these would be perfectly fine as they act as breaktanks.

    In terms of pressure loss over the height, for every 1 meter vertically you go, you will lose 0.1 Bar of pressure, so over 14ft you will lose 0.45 Bar of pressure, then factor in friction loss that you get when forcing water through the pipe, around bends tees etc, i would round this loss upto 0.6 Bar, so your 1.2 bar incoming, will probably be around 0.6 bar at the outlet of the shower.
  12. Bisset2297

    Bisset2297 New Member

    Hi there

    thank you, so if it’s 0.6 bar at the outlet, could I not get an electric shower that will work with a minimum 0.4 bar pressure?

    do you know how much it would roughly cost to fit in a power shower plus changing the feeder pipes to the water tank and hot cylinder?

    I’ve never had this problem before with previous electric showers which is why the blockage theory came up
  13. Nexial

    Nexial Active Member

    If you can find an electric shower that will reliably work on 0.4 bar, then that should work fine (the is if your cold feed is defiantly from the mains and not from the water storage tank).

    A power shower will use both hot and cold stored water, so depending on where your feeds are, it could be a cheap 5 minute job, or a total re-pipe of your shower room.
  14. terrymac

    terrymac Screwfix Select

    What model shower do you have ,is it a T80 ?
    Ideally you should measure the pressure at the shower inlet , I thought it odd that your previous shower worked ,but the new one doesn't.
    If you run it fully cold ,with shower head removed , just the hose fitted,into a bucket for 1 timed minute ,then measure how many litres of water are in the bucket.
    Tell us how many litres it gave in 1 minute.
  15. Tilt

    Tilt Screwfix Select

    Ha ha.......
    Not a five minute job eh, Lol. but I know what you mean.

    @Bisset2297 It only requires a 22mm feed taken from the cold tank to the shower (reduced to 15mm) and a feed taking from the pipework coming from the hot cylinder, so if they are close enough then possibly half a days work, no more than a days work I should think.

    My shower backs onto airing cupboard so very straightforward.
  16. Bisset2297

    Bisset2297 New Member


    yeah my hot water tank is just to the back of my shower unit, water tank is just to the right in the loft

    I’ve bought a shower that works 0.7 bar so will see how this one goes!

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