Quick question for STW Plumbing Massif…

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  • Quick question for STW Plumbing Massif…
  • Premier Icon p7rich
    Subscriber

    We have a 8.5kw electric shower and the pressure is rubbish. Quick question is…will upgrading to a 10.5kw make that much difference? I understand it will be an improvement but i’m wondering how much?? Mains pressure is good and proper power shower, etc are not options. I know more power may require different wire spec n that.

    Premier Icon Stoner
    Subscriber

    8.5kW isnt that small.

    Are you sure the hose hasnt crimped itself?

    grantway
    Member

    Think you may need a water pressure unit

    Low water pressure in shower thread link

    Premier Icon p7rich
    Subscriber

    No crimping or other issues, deffo just a rubbish shower. Anyone know how much diff changing to a 10.5 would make?

    trail_rat
    Member

    Ensure you have a big enough cable for a 10.5 – at least a 6mm depending how far from consumer unit.

    Found mines had been wired up to a 2.5 and had started to melt and burn. !!!!!

    Mines a 10.5 im perfectly happy with it – a mira something or other

    My parents have a cheapy 12kw in their downstairs bathroom and its pish beyond belief ….. Thermostatic mixer in their en suite though.

    Changing from 8.5KW to 10.5kw will not change the water pressure. You may get some increase in flow because it heats the water up a bit quicker but the problem may be elsewhere.

    With the shower on full cold is there good water pressure?

    Does it just reduce as you turn up the temperature?

    If Yes and Yes then there should be some improvement, maybe 10%.

    Are your taps on bath and sink in bathroom flowing well with good pressure?? Could be a couple of things, pipe going to shower not the correct diameter, or a poor pressure in house, i use a 8.5 and its plenty good enough, i had same issue with my taps on bath, hot water wasnt heating on full tilt it had to be half open to enable the boiler to heat better, i dropped down pipe size and now full tilt and boiler can heat enough.

    trail_rat
    Member

    Remove the shower head from the holder , sit it in the bath and pick it up out the back quite a way up the hose , is far away from the head as possible.

    Yu may find the inner hose has crimped up inside the coiled outer.

    Premier Icon p7rich
    Subscriber

    Excellent. Thanks. Yes, pressure is good, i.e. massive when cold. Flow rate is indeed what i’m referring to. Any idea if same rating will give better flow across diff manufacturers? Current 8.5kw model is a Gainsborough and after quick bit of googling their showers seem quite cheap. Worth considering a diff manufacturer to increase the 10% estimate?

    cynic-al
    Member

    I went from a 7.2 or so to an 8.4 IIRC – not a life changing difference but it went from hot & a bit piddly to hot and reasonable on cold days – definitely worth it.

    I got the replacement for free, if I was paying I’d want a bigger jump, tho re-wiring could obviously add to costs.

    Thrustyjust
    Member

    I think the heat exchanger is blocked up and needs descaling.

    Premier Icon footflaps
    Subscriber

    In winter, when the cold mains water temp is a bit lower, shower pressures drop as the rate they flow is limited by their ability to maintain the target output temp – so if the incoming water is cooler, the flow rate drops. A bigger wattage heating element can therefore increase the flow rate proportionally (assuming that is the limiting factor).

    trail_rat
    Member

    Its a gainsborough my parents have that i think is garbage.

    My mira is like night and day compared to theirs despite being lower power.

    Premier Icon geoffj
    Subscriber

    You’d think there should be a shower preheater gadget which you could install to warm the water before it hits the shower unit proper.

    Premier Icon footflaps
    Subscriber

    My parent’s cottage in the Dales has a tiny wattage Mira Sport thing – in winter it just dribbles warm water, almost completely useless.

    Premier Icon cinnamon_girl
    Subscriber

    In winter, when the cold mains water temp is a bit lower, shower pressures drop as the rate they flow is limited by their ability to maintain the target output temp

    has a tiny wattage Mira Sport thing – in winter it just dribbles warm water, almost completely useless.

    Yep, you’re absolutely right! I found this out on the Mira website. In Summer it’s fine but in Winter it can’t be used. The Mira shower in the upstairs bathroom is fine cos it’s not electric. 🙂

    Edit: I replaced both the hose and shower head, they’re regularly descaled but makes no difference.

    Premier Icon p7rich
    Subscriber

    I went from a 7.2 or so to an 8.4 IIRC – not a life changing difference but it went from hot & a bit piddly to hot and reasonable on cold days – definitely worth it

    Interesting. Thanks.

    I think the heat exchanger is blocked up and needs descaling.

    unlikely, it was new a couple of months ago (like for like replacement when the old one went kaput)

    Its a gainsborough my parents have that i think is garbage.

    My mira is like night and day compared to theirs despite being lower power.

    Thanks. Could your parents have lower mains pressure though?

    Makes perfect sense ref worse in winter but ours is poor all year round 😐

    49er_Jerry
    Member

    It’s very unlikely that you’ll have the correct size cable installed for a 10.5kW shower.
    The current require to operate the shower is 45.7 amps. You will DEFINITELY need a 39mA RCD protected 10mm supply cable for the shower.
    A shower is in a special location and as such must be installed, tested and certified by a suitably qualified electrician.

    Premier Icon p7rich
    Subscriber

    It’s very unlikely that you’ll have the correct size cable installed for a 10.5kW shower.
    The current require to operate the shower is 45.7 amps. You will DEFINITELY need a 39mA RCD protected 10mm supply cable for the shower.
    A shower is in a special location and as such must be installed, tested and certified by a suitably qualified electrician.

    Thanks Jerry. Yep, first job on the list (assuming there’s some benefit in more kWs) is to get an electrician round.

    alanl
    Member

    Actually, you may not need any more than a 6mm cable.
    6mm T+E can carry 47 amps if clipped direct to a solid surface and doesn’t go through any insulation.
    Also, all manufacturers shower ratings are generally done at 240V, so a 10.5kW shower at 240V sounds better than the 9.4kW at 230V which you will likely get.

    alanl
    Member

    Also, if it is a like for like replacement, anyone can do it. That means just the shower unit being changed. A change of cable could be argued either way, but if the protective device (the fuse/CB) is changed then that needs notifying.
    If you have no RCD now, there doesn’t have to be one if you do a like for like change, though it makes sense to fit one if you haven’t got one.
    If a new install, then it should be notified under Part P of the building regs.

    trail_rat
    Member

    Of course alanl is referring to if you are in englandshire.

    Parents have a thermostatic mixer upstairs thats not pumped its amaizing

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