Least disruptive way to ensure two showers can run at the same time

[Rachieble]

We're converting our old family home into an HMO to let out as 4 rooms. It will have 2 bathrooms - 1 shared between 3 rooms, and one bedroom with an en-suite. When I say 'convert' it really doesn't involve a whole lot of building work because the house was all renovated for us to live in and mostly everything is in place - the bathrooms are all built and fitted already. But I'm aware that my tenants may want to use both showers at the same time, and obviously want to make sure that they can do that with reasonable water pressure to do so. At present the house has a combi boiler - when we lived there we'd never use two showers at the same time so it really wasn't an issue. There is precious little space for an unvented cylinder as the loft is converted to a room and there is no airing cupboard or header tanks or anything like that. I had hoped that perhaps we could fit an electric shower (a top quality one like a mira sport which promises 30% extra flow) in the main bathroom (mostly to ensure we'd always have a working shower if the boiler packed up, which would be supported by the shower on the bath tap if the electric shower packed up) and rely on the thermostatic mixer off the combi perhaps with a flow restrictor for the loft en-suite, plus flow restrictors on all the taps. But from my rather rudimentary tests, our water flow rate is only about 10l per minute and I'm not sure this would be enough? Will this work? Or do I need to upgrade the mains?  Any other suggestions? Thanks

 

(anyone who read my previous thread, please disregard it as our plans have now changed, hence the new question). 

Edited December 16, 2021 by Rachieble

[Faz]

Won't work off a combi - and with that mains pressure you are going to need an unvented cylinder and I would have thought and even then it would be shite.  10ltrs/m is the boarderline for the definition of low water pressure.

[Marvin]

 

1 hour ago, Faz said:

Won't work off a combi - and with that mains pressure you are going to need an unvented cylinder and I would have thought and even then it would be shite.  10ltrs/m is the boarderline for the definition of low water pressure.

Plus 1  

Typical low flow shower 12 litres per minute. How do you cope???

 

As for upgrading the mains... it depends what is in it. 

 

You have the flow and the pressure. If you increased the size of your supply pipe to your home the flow could increase if the pipe restricted the flow. However, it would not increase the pressure as this is controlled by the water company supplying the water in your area.

 

I would suggest contacting your water company to ask them about what could work for your home. ( it could be you are a very long way away from a main...)  Secondly I would ask your neighbours what sort of set up they have. (i.e. are you the only one with a poor flow rate). 

 

Good luck.

 

Marvin 

[Temp]

4 hours ago, Rachieble said:

I had hoped that perhaps we could fit an electric shower (a top quality one like a mira sport which promises 30% extra flow)

The flow rate available from an electric shower depends on the power rating of the shower (in kW) and the temperature of the incoming and out going water. So it's slightly  lower in winter than summer and you get a higher flow rate if you turn the output temperature down. All things being equal a higher power (more kW) will deliver a higher flow rate.

 

So if I saw a claim like "30% extra flow" I'd want to know they were comparing like with like and how they justify that claim.

 

Edit: This assumes the flow isn't limited by the mains !

Edited December 16, 2021 by Temp

[Temp]

4 hours ago, Rachieble said:

from my rather rudimentary tests, our water flow rate is only about 10l per minute and I'm not sure this would be enough? Will this work? Or do I need to upgrade the mains?  Any other suggestions?

 

How/where are you measuring it?

[Rachieble]

5 minutes ago, Temp said:

 

How/where are you measuring it?

As I say, very rudimentary, I timed how long it took to fill a 1l jug from the kitchen cold tap (so just over the rising main) using a stopwatch. 1l in 6 seconds. 

[Temp]

OK as a check try measuring the kitchen flow rate again while another tap is running elsewhere in the house. Do they still add up to 10L/min.

 

You also need to know the static pressure to make an informed choice on solutions.

[Marvin]

1 hour ago, Temp said:

OK as a check try measuring the kitchen flow rate again while another tap is running elsewhere in the house. Do they still add up to 10L/min.

 

You also need to know the static pressure to make an informed choice on solutions.

Always best to time how long it takes to fill a bucket and measure out the contents in litres. This gives you a better indication of your flow rate. 

[SteamyTea]

What does it say here about shower flow rates?

https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/504207/BR_PDF_AD_G_2015_with_2016_amendments.pdf

Edited December 17, 2021 by SteamyTea

[Pocster]

I needed 5 showers to run simultaneously.

4 off a big uvc . But it couldn’t manage 5 . So the main bathroom shower is electric fed off a cold header tank . Noisy but works ( also if uvc fails still a working shower available )

To clarify it’s a specific type of electric shower that plumbs to a header tank I.e not mains fed . 

Edited December 17, 2021 by pocster

[Rachieble]

1 hour ago, pocster said:

I needed 5 showers to run simultaneously.

4 off a big uvc . But it couldn’t manage 5 . So the main bathroom shower is electric fed off a cold header tank . Noisy but works ( also if uvc fails still a working shower available )

To clarify it’s a specific type of electric shower that plumbs to a header tank I.e not mains fed . 

Sadly we don't have space for an uvc or a header tank as the loft is already converted into a bedroom and there's nowhere higher to go.

[Pocster]

Just now, Rachieble said:

Sadly we don't have space for an uvc or a header tank as the loft is already converted into a bedroom and there's nowhere higher to go.

No eaves to use ?

[Rachieble]

11 minutes ago, pocster said:

No eaves to use ?

Not really big enough for a tank without ripping out all the walls, and anyway, nowhere to run the pipes across as the eaves are on the other side of the house. Eaves are at the front and the bathrooms are both at the back under the dormer. There's a massive steel across the floor of the dormer side that the exposed loft floorboards are laid directly onto. It'd be a massive job to drill through to run pipes. I think its a no go really. 

[Pocster]

7 minutes ago, Rachieble said:

Not really big enough for a tank without ripping out all the walls, and anyway, nowhere to run the pipes across as the eaves are on the other side of the house. Eaves are at the front and the bathrooms are both at the back under the dormer. There's a massive steel across the floor of the dormer side that the exposed loft floorboards are laid directly onto. It'd be a massive job to drill through to run pipes. I think its a no go really. 

Sounds like a dog ! Must be somewhere to stick a cold tank and ‘pump’ to showers . Ceiling height in bathroom/ ensuite not high enough for a narrow long tank ? ( seen these whilst abroad ) 

[Onoff]

17 minutes ago, pocster said:

Sounds like a dog ! Must be somewhere to stick a cold tank and ‘pump’ to showers . Ceiling height in bathroom/ ensuite not high enough for a narrow long tank ? ( seen these whilst abroad ) 

 

Coffin tank?

[Pocster]

10 minutes ago, Onoff said:

 

Coffin tank?

Don’t need much height . Mount directly above shower . Enough ceiling height though ???

[Rachieble]

No ceiling above the shower in the loft conversion. The room only has about a 2m high ceiling height and the shower head is pretty much right up at the ceiling already. Might be able to manage a cold water tank above the main bathroom shower, though the extractor is there already and the other wall has a window. But wouldn't that just look hideous? Its a pretty tiny bathroom - only 1.7mx2m so not much room for extra bits and bobs. 

[Rachieble]

I wonder if I'm misunderstanding this. Is the suggestion that I mount a tank on the wall in the bathroom to give more pressure to an electric shower? And then I'd need a pump too? Can anyone point me in the direction of the sort of thing I need as I can't find anything but maybe I'm googling the wrong thing. I've googled coffin tank but that looks like something that needs to be hidden in the loft which wouldn't work. The only possibility I have would be to install something visible high up on the bathroom wall, but that would need to more akin to an old fashioned toilet cystern as the bathroom is tiny and has barely any space to put anything extra in there. And obviously would have to look ok as well as this is quite a high end house in terms of style. Just to give some perspective, this is the bathroom so you can see how small it is and how little extra space there is. 

 

Edited December 17, 2021 by Rachieble
Added photo.

[Pocster]

13 minutes ago, Rachieble said:

I wonder if I'm misunderstanding this. Is the suggestion that I mount a tank on the wall in the bathroom to give more pressure to an electric shower? And then I'd need a pump too? Can anyone point me in the direction of the sort of thing I need as I can't find anything but maybe I'm googling the wrong thing. I've googled coffin tank but that looks like something that needs to be hidden in the loft which wouldn't work. The only possibility I have would be to install something visible high up on the bathroom wall, but that would need to more akin to an old fashioned toilet cystern as the bathroom is tiny and has barely any space to put anything extra in there. And obviously would have to look ok as well as this is quite a high end house in terms of style. Just to give some perspective, this is the bathroom so you can see how small it is and how little extra space there is. 

 

You get get an electric shower that uses gravity from the tank to feed it . Out at the moment a link not easy . @Nickfromwales knows what you want .

[Rachieble]

3 minutes ago, pocster said:

You get get an electric shower that uses gravity from the tank to feed it . Out at the moment a link not easy . @Nickfromwales knows what you want .

That's what I thought. But the tank would have to go visibly on the bathroom wall then as there is nowhere above? you can see how little space there is so it'd have to be something tiny (if you look closely you can just see the top corner of the room above the extractor fan). This is the bathroom above, which has even less space (stacked directly above this one), and I've attached picture of the bedroom in the loft, to show you how little eaves space there is, and obviously already finished with radiator and no real access - eaves about 5m across the house from the bathroom on the wrong side. 

[SteamyTea]

Do you know what flow rate you have coming into the property?

[TonyT]

Cupboard to the left of the radiator?

[Onoff]

Water bed? ?

[Rachieble]

18 minutes ago, TonyT said:

Cupboard to the left of the radiator?

Its tiny though. And I can't get any pipes across the floor to the bathroom at the other end of the house due to a huge steel cutting it in half - the floorboards are laid directly onto the steel and there is no gap.. 

[Rachieble]

No, I need to get this checked. We're in quarantine at the moment so I can't go up there until after Christmas.