A bit random I know, does anyone have any experience of electric showers as in what brand or model is best, Mira or Triton for example? It’ll be gravity fed via a cold feed from the tank in the loft. @Dunc I seem to recall that you’re a plumber - have you any thoughts? I’m literally asking for a friend who is renovating their house and needs to get this right. Cheers.
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If gravity feed then you need to buy the right model for the job.
Most would not work due to the very low pressure you will have.
Is your mains water a problem, as in low pressure, or poor flow rate?
I will take a look and see what models i would recommend.
A electric shower as in a one that heats the water as you use it, these need a min 1 bar (working) and a min flow rate of 8 litres a minute, but really you need more like 1.5 bar, and 11 litres.
A mains booster pump could be the answer, or a hot, and cold feed shower with a pump, would probably be the way to go.
Or if your mains water isn’t a problem then change the pipe to mains, rather than tank.
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ah cheers dunc much appreciated. The cold mains has inconsistent pressure and oscillates between high and low so an older electric shower in the house runs very hot one minute and cold the next as the pressure varies, hence we think a tank fed unit would be best. I was looking at the Mira Elite SE Dual which seems to fit the bill and has a reasonable flow rate. The other issue is the loft tank is not huge - about 140 litres but I think it should be ok as long as very long showers are not anticipated. Edit, they want an electric shower for the convenience of having always available hot water without the need to have the immersion on in advance, two young girls in the house and showers could be at any time!
The mira should work ok with what you want to do.
Also you can change the probably standard part 1 or 2 ball valve in the tank for a much bigger 3/4 ball valve, this will give a much larger flow, and so fill the tank much quicker. So you don’t run out off water.
The 3/4 ball valve is much better than putting 2 standard ball valves in the same tank.
But there are a few electric showers on the market that will do it with low pressure, or flow problems, but as said you need to be careful which one you go for, but it looks like you are on the right tracks to sort it.
ok great, so ideally you’d have a 3/4 pipe rather than 1/2 feeding the tank along with the 3/4 ball valve?
You could but no, not really. The 3/4 valve has a much larger hole for the water to pass through compared to the standard valve. This is still smaller than the internal diameter off the 15mm pipe you will have feeding the tank, so 22mm pipe isn’t really necessary. But it would be better to have if a new pipe is being put in, even if its a bit over kill.
Ok thanks, yes the plumber is running a new qualpex 1/2 inch (whatever that is in mm) to the tank, I’ll suggest the larger ball valve as I agree that tank recovery time here will be of big benefit and could make all the difference. Thanks again for your help 
No problem
Qualpex is just a make of plasic pipe
Yep I know
Sorry i didn’t read it correctly, its 15mm pipe, but thats outside diameter, but the inside will be less, especially when inserts are fitted.
It will be more restricted than say a copper pipe of the same outside diameter. But obviously much easier, quicker, and less joints. So you can argue all day over the pros and cons off each.
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I’ve had a Mira Galena (slate effect) and it’s performed well without any problems for 6 years, used once most days. This is in the downstairs bathroom with a mains water booster pump.
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Aqualisa digital showers are great. They take a feed from the cold tank and the hot water cylinder, combine the two and then pump it, so you get a great shower with good pressure.
Make sure the electrician doesn’t wire the live and neutral the wrong way round as one did at my mate’s house. 
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The booster pump is a great way to increase water flow and pressure, but you can only boost so much, if you haven’t got the water flowing enough into the pump to start with.
It looks like the main poster has this problem, so unless you fit a big buffer tank to the mains, then a booster pump could run dry, and if this happens it will soon burn out.
So he really needs the cold water storage tank in the loft, as this is effect is the buffer tank, and then a pump to boost it for the shower.
The next slight problem is they want an electric shower, now these normally run off mains feed water, and not gravity from a tank, as the pressure would not be sufficient to operate the shower.
Cheers
Yes my thinking too about the pump but I gather the Mira elite (tank fed) has a built in booster pump to overcome the potential lack of pressure from the tank whereas the mains versions have no additional boost and rely solely on incoming pressure
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Correct
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