Space efficient plumbing strategy for 5 showers?

why not go all electric? no gas safety concerns and only one bill

Probably need mains pump to run all five showers at the same time?
Try an unvented cylinder in the loft, mounted horizontally for stored hot water. Far better than electric showers anyway.
3 phase supply? Why? the single phase supply should be rated at 80A or thereabouts. Are you proposing to put in a 3 phase board? IEE regs would then apply due to distance between the phases etc.
Perhaps you intend to rewire anyway?
Unvented cylinder the way to go. Two can even be coupled together if necessary, although it is unlikely that more than a 210 litre tank would be necessary. Is the boiler suitable to replenish the tank within a reasonable time frame?
Unvented cylinders rated at a flow rate in excess of 40 litres a minute.

Steve

Reply to the comment left by terry sullivan at 19/03/2018 - 11:28
Hi Terry, I was planning on installing the combi mainly to heat the house as it’s more efficient than electric.

Electric showers dont have a lot of power and rely on mains pressure. If 2 or 3 people try using at the same time or other water usage like Wasing machine or sink there will not be enough pressure for showers. Go with previous advise speakers to a plumber and install a pressurised cylinder suitable for the job.

Reply to the comment left by Stephen Smith at 19/03/2018 - 11:45
Hi Steve, I guess that the only way to provide the flow that 5 showers need is to use a tank. Good idea about a horizontal one in the loft, I’ll look into the space right at the top of the apex. The reason I was considering 3 phase was that I was thinking of having 4 electric showers. If I need a tank then it may as well be a hot water tank so maybe I’ll stay with single phase electric.

Reply to the comment left by Recardo Knights at 19/03/2018 - 11:56
I agree with Stephen an unvented cylinder is the way to go and more economical.
You can still install a combi and use an “s plan “ with two motorised valves therefore the benefits of a combi and a systems boiler. A good gas safe engineer will advise accordingly.

Hello this is not answering your question, but to suggest that if you are planning to install en-suites it may be advisable to contact your local council. The installation may mean that the council may request council tax on each room and not the house as a whole. Councils are trying different ways to raise money.

Reply to the comment left by Robert Taylor at 19/03/2018 - 13:22
Hi Robert, my understanding is that as long as there are no cooking facilities in each room then it will be treated as a single dwelling. Students are exempt from Council Tax, but I will double check with the Council as I don't want any nasty surprises!

Hi, remember unvented runs of mains pressure, if you have 2 showers run at once your going to notice a drop in flow, I think even adding an accumulator you still may struggle with 4 or 5 showers!
Thing is to have low KW electric showers so the flow is lower than hi KW showers, your going to need a lot of water to supply 5 or six showers! just in case over half of them are used at the same time. I seem to recall 10.5Kw elec showers give a flow of around 9litres a minute, a reasonable combi around 12 l/m.

Similar job - One house split into 6, each room with worktop and ensuit. One electric meter per room so each tenant worries about their own electric.

The 3 ground floor rooms are of the mains water supply. 7.5Kw showers. The 3 first floor showers are off a tank in the loft with a 3bar pump, if all first floor showers are used at once it is like a 1bar supply to each shower (mains pressure minimum is around 1bar so the electric showers will still work).

Interesting little project 😉

Remember also the speed of water supply through a pipe. Makesure that you fit a large bore mains water supply pipe for as far as you can as otherwise the tank will empty and suck air into the pump stalling the whole thing and making a noisy whine