New bathroom advice

13 Jun 2015
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United Kingdom
Hi folks,

Looking at moving a bathroom from downstairs to upstairs, and one of the main concerns I have is getting a decent shower. Have wasted thousands trying to get a decent shower in my current house over the years, and still have a temperamental crap shower, so a good shower would be high on our list of desirableness. I've been reading advice and guides on bathrooms/showers/water systems and seem to be going around in circles, so thought perhaps this may be a good place to get some thoughts on our case.

The house has oil heating, small header tank in the attic, hot water tank downstairs (below new room for the bathroom). Unsure about the mains water pressure unfortunately. It was fine when I've checked, but it's easily possible that it shares with other houses, so may fluctuate (we don't have ownership yet, just trying to plan ahead). So, best to assume pressure could be an issue?

What we would like is;

a) Hot shower without the need to wait on water heating or turn the heating on (current situation with a 'power' shower).
b) Ability for several people to take a shower in sequence without running out of cold/hot water.
c) Decent pressure for once.

My concerns are;

a) Electric showers I've had don't output much water.
b) Power showers require the hot water to be ready, which may or may not be the case.

So is there any way to overcome the potential lack of hot water, without the lack of pressure in the shower that I've experienced with electric showers? And if there are pressure issues with the mains feed, what's the best option (assuming mains pressure is needed) ? Mixer showers look so much nicer than having an electric/power shower unit in the shower, so would be interesting to know how to provide the necessary hot water/pressure for those on such a system.

Many thanks,

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a) Hot shower without the need to wait on water heating or turn the heating on (current situation with a 'power' shower).
b) Ability for several people to take a shower in sequence without running out of cold/hot water.
With a hot water cylinder, those are achieved by having a cylinder of suitable size, and setting the boiler to heat the water in it at the required times.

c) Decent pressure for once.
This depends on how the cylinder is supplied. If it's a mains supplied item, then pressure and flow are dependant on the cold mains water supply.
If it's gravity fed from a tank in the loft, then a pump can be installed to provide the required pressure.

a) Electric showers I've had don't output much water.
b) Power showers require the hot water to be ready, which may or may not be the case.
All electric showers are severely limited in flow, due to them having to heat the water as it is required. Too much flow = cooler or cold water. They are far worse in the winter as the incoming water is colder. Best avoided unless that really is the only option.

b. is easily resolved as above by setting the controls properly.
As you are moving the bathroom upstairs from downstairs, that is only going create more issues on decreasing water pressure.
The only way you can reliably deliver what you are looking for is to -

1) Have adequate cold water pressure and flow - you need to have that tested and establish that it is suitable
2) Have a system to heat that water instantly whilst still supplying an adequate flow and pressure.

If feeding the shower from hot water storage is out of the question as the reheat time is not quick enough for you using a HW cylinder then you only really have two other options.

1) Thermal store for instantaneous hot water at mains pressure
2) Decent sized Combi boiler with the single hot water outlet feeding the bathroom. Other hot water outlets fed by a hot water cylinder heated by the boiler.
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Larger Albion superduty cylinder + shower pump + fairly powerful system boiler? Just a thought.
Thanks for the suggestions guys, that's interesting.

So with a combi boiler, you're limited by how fast it can heat water, whereas with the system boiler, you're limited by the size of the hot water cylinder? Would the combi boiler option not have potential pressure problems?

Both of those options seem to be in around the same price when you factor in the tank for the system boiler; albeit I'm not clear on the different options available.

Many thanks,

A combi boiler works in a similar way to an electric shower- water is heated on demand, therefore the flow is limited by the amount of heat that can be put into the water.
A combi boiler is around 3x more powerful than an electric shower, but the limit on the amount of water you can get out of it is still there, as is the fact that in the winter, the flow rate for a given outlet temperature will be lower.

You mention 'pressure' a lot - do you mean pressure or flow?
Hi Flameport,

Thanks for that clarification.

Afraid I don't know the difference between pressure and flow. I just don't want another weak dribble coming out of the shower, whether someone else is running water, next door is running water or otherwise. So whether that's pressure or flow, I don't know.

Just to be clear, a superduty cylinder has a very effective coil that can sink nearly 30kw, idea being that the water would reheat nearly as fast as you use it.

High output combi would be OK (in the sense of adequate, not perfect) provided mains supply is good enough. But no immersion backup.

Another alternative would be to get a new supply put in from the street if the pressure and flow are enough.

If you want successive showers from a fast recovery cylinder you will need a large cold water storage cistern in the attic.
To ensure you have a suitable system, I would start with the pressure and flow of the incoming supply. That's your first priority before you even decide on the HW System.

Pressure = The force exerted by the water - measured in Bar or PSI (dynamic/static - flowing/not flowing)
Flow = The volume of water over a given time - Measured in Litres per Min (L/Min)

You really want at least 3 bar with as high a L/min flow as you can achieve, 12L/Min being the min and more if achievable. Once you have that then you can decide the HW system you will be happy with.

The reason I suggest a combi is a reasonable boiler will output 12L/Min at the mains pressure & usually 3 bar max , more than enough for a great shower and it's the easiest overall installation IMO. Thermal store is hot water at mains pressure.

You already ruled out a power shower, did you not? Therefore is a tank a consideration? The fast recover cylinder's are great but even they, when on the larger side, still have a 10-20min recovery time to re-heat all that water.
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Sounds like an approach. I've had plumbers (repeatedly) test pressure before, but not flow, now that I see there's a difference. :) Don't worry, I'm not going to attempt to do this myself, just trying to find out what we should be looking for rather than take advice from suppliers. Hasn't worked out well in the past!

Ruled out a power shower because, at least with our current setup, it gets through most of the tank of hot water in one shower (when it's working). So a larger cylinder would solve that. The other half prefers the look of mixer showers though, since they don't have a big unit in the shower itself.

Edit: as an aside, is it possible with an oil boiler just to heat the water and not the radiators? Never had a combi boiler so I'm not entirely sure if that's an option or not.

Flow is an easy one. Open the cold water tap that's closest to the mains stop cock fully and fill a litre jug, time how long it takes, divide 60mins by the secs it took to fill = L/Min.
You do get oil fired combi boilers, they don't supply instantaneous hot water tho rather than they hold store hot water I believe. If yours is a system boiler, i.e. runs the rads and a hot water cylinder then it wouldn't supply instantaneous hot water.
You would need to change the boiler. A thermal store may be an idea given your current setup.
What size of HW cylinder do you have at the moment?
Just been reading about thermal stores, those aren't something I've come across before. Seems like a really good idea, particularly when we were already considering installing a wood burning stove. Do those have to go upstairs? How does that work with a system boiler then? It heats the water in the store and that provides hot water/heating? More thinking summer time when I'm guessing we wouldn't want to use a wood burner.

Current cylinder is about 120l I'd guess.


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