How many power showers off one tank?

22 May 2017
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United Kingdom
Hi everyone, looking for some advice about running 3 aqualisa quartz showers off a 300 litre megaflo... The aqualisa shower consumes 12 liters a minute.

We currently have 1 aqualisa quartz and two thermostatic showers but are now renovating two of the bathrooms. My sister and I shower at the same time in the mornings and when she has her aqualisa on the pressure drops on my thermostatic by probably about 30%ish. I am against having another aqualisa shower but told my mum she could go for another aqualisa since she does not shower at the same time as either of us.

Now she wants all three bathrooms on aqualisa quartz systems which I think is just too much in terms of pressure loss. Hot and cold is fed to tank/balancer with 22mm and 15mm to each shower. Am I right in saying that one aqualisa should be used at a time and that three is too many taking into consideration tank size?

Any input would be gladly appreciated

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That is an electric shower. An electric shower heats a cold mains water supply.

You would not run an electric shower from a megaflo. A megaflo is a hot water tank.

You would not usually take hot water and try and heat it, it's already hot.
Hi, I'm not talking about the Aqualisa electric showers, I'm talking about the quartz range, they have a digital 'processor' unit concealed and can be fed from a tank/combi or gravity tank depending which processor you choose.
I'm looking at a Quartz, it says it's an 8.5kw shower.

Do you have an actual specific model I could look at?
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I see, well yes you can use that on a megaflo, but how many at once will depend on pressure and flow of your mains.
OK, so it's a case of testing mains water flow and seeing if it's high enough to run two of them at once (our requirement). I just double checked and it appears they don't publish litres/minute for the high pressure /combi unit which I presume is becuase of varying flow rates between instillations.
If the pressure/flow aren't adequate, I believe an accumulator may help. But wait for a grown up to comment. I am in no way shape or form a plumber or heating engineer.
An unvented cylinder (megaflo is just one brand) can deliver mains pressure hot water to any number of outlets. Just like a combi but has stored rather than instantaneous DHW which means they can deliver it at full mains rate.

Performance at an outlet, in terms of pressure and (more importantly) flow depends on the incoming main and the number of additional outlets that are opened (including cold outlets such as wc's/washing machines/sinks etc).

Internal bores of all supply pipework is also a factor.

Improvements can usually be obtained by upgrading the incoming main supply from the suppliers stopcock into the property to the inlet control group. Comparing flow and pressure at the suppliers stopcock with flow and pressure at a non restricted cold outlet, within the property (washing machine feed or outside tap) will help determine if this is a worthwhile undertaking.

And, not to forget... Once the cylinder has been depleted of hot water, it will need ## minutes to regenerate/recover and this time will depend on the DHW heating setup.

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