The eternal shower question - recommendations wanted

We are installing a shower in a new, downstairs shower room, it's to be a wet room so it won't be in a shower cubicle, just wall mounted in a room about 1.8 metres square.
We have an 'old fashioned' CH and hot water system with a hot water cylinder heated by an immersion heater (in summer) and an LPG gas boiler in winter. Since we're LPG (not town gas) the difference in cost between electricity and gas is probably not all that much.
The choices would seem to be:-
Electric shower - i.e. electrically heated, running off mains pressure water. Our water mains pressure is quite high, a bit over 5 bar, so flow rate would not be an issue. The only issue is how much flow rate the electricity can heat. Disadvantages - Are 10kW showers acceptable? Advantages - quite simple and cheap, instant availability of hot water.
Gravity fed shower - Flow rate limited by gravity, not by heating capacity (until the hot water runs out), but low pressure so not a 'power shower' by any means. Advantages - quite simple and cheap, not power limited. Disadvantages - low flow rate, takes time to get to temperature.
Pumped shower - similar to gravity feed but more 'power shower' with a pump pusing the water out. A bit more complicated. Advantages - good flow rate, not limited by available power. Disadvantages - not instant heat up, will run out of hot water eventually.
So, what do the team think? My inclination is to go for a 10kW electric shower (or are they only 9.5kW now?) as being relatively easy and having 'instant on' and controllability better than the others. The CU will be very close so that bit is quite easy.
--
Chris Green
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Chris Green wrote:

Actually if I have a long shower, I usually run out of cold in the loft tank, before I run out of hot in the cylinder ... I do have the thermostat on the cylinder turned up pretty high, but don't have the shower mixer set to blistering hot.
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On 31/07/2019 11:22, Andy Burns wrote:

Sticking a better inlet valve (or a pair of them) on the cold cistern should fix that.
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John.
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John Rumm wrote:

I've got a bigger cold tank (the existing one is completely uncovered) and a nice Pegler full-bore lever valve waiting to be fitted, but awaiting finishing boarding that end of the loft.
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On 31/07/2019 11:15, Chris Green wrote:

10kW is an perfectly adequate shower normally IMO, but less so when the input is very cold in winter. It's not a jetwash. It all depends on your expectations - a typical middle class American might regard a 10kW shower as puny, a typical UK landlord would regard a 7kW shower as luxurious.
Cheers
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Clive

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On 31/07/2019 12:22, Clive Arthur wrote:

Mains pressure tank heated by CH boiler AND immersion
No pumps needed
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This makes me unfit for the company of people of a Left persuasion, and
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On 31/07/2019 12:37, The Natural Philosopher wrote:

16kw from boiler, 3kw from immersion and some from the solar thermal panels some days if needed which is never IME.
200l tank at 80C holds a lot of water for a shower.
On the other hand the shower can deliver over 20l a minute from the soaker head so it could run cold with just the boiler heating the water. Its never happened yet and the boiler is set on at the times we shower anyway. Its set quite late so the solar panels work better.
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On 31/07/2019 11:15, Chris Green wrote:

10kW will get you about 4 lpm in winter. With the "frugal" (i.e. narrow spread of fine jets) shower head, it will do then job, but may be disappointing if you are used to a conventional mixer shower.

If carefully piped, and the unit selected is designed for low head use, then that can work well.

and sooner than on gravity alone.

Other options to consider:
Venturi shower - take cold mains and tanked hot to the shower, and the mixer uses the cold pressure to pump the hot. So like a pumped shower but no pump, noise, and complication.
Or the "top end" solution, replace the DHW cylinder with an unvented one, and have (close to) mains pressure HW everywhere.
--
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John.
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On Wed, 31 Jul 2019 12:29:47 +0100, John Rumm wrote:

Yep about 4 l/min to a sensible temperature (not that barely warm 43 C "safe" nonsense) . The electric shower here is fed via a PRV which brings the mains presure down to a managable 2.5 bar (ie you don't have to remember that if you open a tap a lot the water will hit the sink/basin and bounce straight out...)
If you put the shower to fully cold, it's rather too fierce. Heating the water drops the flow rate considerably. It's OK, does the job, it's not a warm dribble but Ideally I'd like a little bit more flow.

heating

You're going to have about nearly 1 bar with a ground floor shower and loft tank in a two storey house. Choose a shower designed for a LP system and it'll drown you... HW straight from an essex (wessex?) flange on the top of the tank.

easy

others.
Our electric "runs on" for a few seconds after the stop button is pushed to cool the heater. It's less controllable than a tap... Mira Sport IIRC.
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Dave.
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On Wednesday, 31 July 2019 11:16:04 UTC+1, Chris Green wrote:

My mum had a Mira Advance Flex in her wetroom, they seem to be popular with accessible bathroom/wetroom refitters
https://www.mirashowers.co.uk/showers/electric-showers/mira-advance-flex-98kw/
It wasn't a powerful jetwash but the sort of soft foamy spray overall gave a very good account of itself even in January. An advantage of not being too powerful is when the head is dropped it doesn't firehose all over the ceiling.
Triton do similar.
If looking at mixer showers look for TMV3 certification for anti-scald.
Advantage of gravity fed - will work even in a power cut if you have stored hot water, or an inverter to run the LPG boiler controls.
Owain
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On Wednesday, 31 July 2019 11:16:04 UTC+1, Chris Green wrote:

of course

trivial

fairly quickly, not eventually

I lived with high flow rate showers for years. They're pointless & waste mo ney.
One way to get a low power or limited storage shower to do better is to add a drain heat exchanger. I estimated about £50 or 60 to diy one.
NT
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On 31/07/2019 11:15, Chris Green wrote:

You'll have plenty of gravity head if you have water in a tank in the loft of a typical 2-storey home, being that your room is downstairs.
I have a downstairs shower, and the downpour is pretty powerfull, enough to feel 'pressure washed'.
How about doing a test with a garden hose connected to a tank supply and see how wet you get?
--
Adrian C

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On 31/07/2019 11:15, Chris Green wrote: <snip>

We replaced a gravity fed one with a thermostatic gravity fed one, and we're quite happy with it.
The shower head is about the size of a tea plate, and gives a gentle spray all over.
Our ceilings BTW are only about 2m. You probably have more head than us.
Make sure you get thermostatic. Warm up faster, and more stable even if someone else flushes a toilet!
Andy
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On 04/08/2019 21:43, Vir Campestris wrote:

More importantly for gravity fed, make sure that you have a Surrey or Essex flange for the hot water feed from the hot water cylinder.
Since fitting a Surrey flange, our shower doesn't vary at all, even when someone turns a hot tap on.
By the way, why is it called a Surrey flange, when it is threaded, not flanged?
SteveW
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