Enough water for a good shower?

[Pete Verdon]

Hi,

I'm looking at showers for my bathroom refit, in which I'm ditching the bath in favour of a really good shower. I now have enough space for a nice big stall; the other side of a "really good shower" is the water stream itself. Hopefully the group can help me figure out what my system can manage.

I have a combi boiler, specifically a Brittony Combi SE. I don't actually know if it's the 80 or 100 model; let's be conservative and say it's the smaller 80. The specs for this are:

Heat Output C/H & DHW: 9.5 to 24 kW DHW flow rate at 30ºC: 11.4l/min DHW flow rate at 35ºC: 9.85l/min

I've just measured the water pressure at the existing shower outlet. With hot tap, cold tap, or both, opened slowly, the pressure is a solid

3.2bar.

The bathroom shop I went to do point out the importance of making sure that your supply can cope with your shiny new 50cm shower head or whatever. However, the *only* number they work with is the water pressure. It seems to me that the flow capacity matters too, and so does the ability of the boiler to heat that much water. The l/min at 35º is a bit meaningless to me, as I have no quantitative idea of how hot I normally have a shower, or how much water is "a good amount". I do know that for this "sheer bloody luxury" bathroom it's going to be hard to have too much :-)

Any pointers, rules of thumb - or ways of finding out how much water a given shower head needs when only minimum pressure is quoted - appreciated.

Cheers,

Pete

[pete]

Following a discussion a long time ago about the amount of water saved by using a shower instead of a bath, I stuck a bucket under the shower to see how fast it filled. I arrived ata figure of 10 litres per minute. Obviously, the flow rate depends on pressure, shower head size & config. BTw, a bath used about 50 litres, so the breakeven point is 5 minutes.

[Dave Plowman (News)]

I have an Aqualiza low pressure thermostatically controlled shower fed with 22mm both hot and cold from a storage system. This gives a max flow of just over 20 litres/min at any temperature you want up to 60C. I wouldn't want any less flow than that - although of course many are happy with much less.

[Appelation Controlee]

-------------------8><

You've obviously never showered in a German hotel (or a German home, for that matter). ;-)

[Rob]

If you're darned lucky enough to have a shower over the bath, just leave the plug in. My more rigorous ablutions only fill the bath up to my ankles - so about 4 showers per bath.

Rob

[The Natural Philosopher]

My wife can fully empty a 250l hot water tank in the shower.

Mains pressure and 22mmm all the way..to a massive shower head.

[Tim S]

The Natural Philosopher coughed up some electrons that declared:

Thanks - I'll put a flow restrictor on mine

;->

[Tim Lamb]

Likewise daughters. I suspect it is something to do with shaving their legs but couldn't possibly comment further..

Mine is pumped to an Aqualisa thermostatic mixer and head.

regards

[The Natural Philosopher]

Well once its empty, it goes cold. That gets her out.

Everyone who uses it says they have never experienecd a shower like it.

I cant stand in it going flat out. I get washed away.

[Huge]

So what's the point? I want to *enjoy* my shower. Not just get dripped on by some lukewarm water.

[Bruce]

Sounds more like a torrent!

Or a private waterfall ...

[The Natural Philosopher]

I think that sums it up pretty well.

A standard waste can JUST about drain it as fast as it comes out, if not too much hair is clogging it.

I don't often use that one, but when I do it is brilliant. I don't use it flat out though. This one really does go up to 11...

[Pete Verdon]

Well, that's sort of my goal, although I suspect I'll have to settle for less as I doubt my boiler is up to the task.

Pete

[John Rumm]

Indeed it does - more so than static pressure.

Well if you think that electric showers in the 4 lpm range are really poor - in the "run around to get wet" category. 8 - 10lpm will give what most would think of as an ok shower - especially if there is a bit of water pressure behind it. For body jets or big soaker heads then you are looking at 15lmp or more. The biggest consumers probably pushing consumption at 30lpm. Doing more than 18lpm with an off the shelf combi is going to be hard work (especially if you want spare capacity for other users of hot water at the time). [dribble will be along to disagree obviously].

[Tim S]

Huge coughed up some electrons that declared:

Mine would potentially run at 7.5 bar.

I fear for the "lads" if the spray is misdirected!

[The Natural Philosopher]

well if you have a combi, you are shafted from the word go.

I'll leave you to work out what 25 liters per minute raised from 2 deg C to 50C represents in terms of power input.

Probably 80KW at a guess..

[Pete Verdon]

Great - real numbers are exactly what I was after :-)

I've looked at the flow restrictor in an old valve that I replaced in the boiler, and find that it is white. Apparently, this means that it is the higher-flow version, and hence that this is the SE 100 boiler rather than SE 80. There appears to be no other way to tell, so good job I had the old part rather than draining down to look at it :-)

That means that my rated flow is 11.48 l/m at 35 degrees. I also have a better handle on temperatures now, since I've realised that the nanny-stop on thermostatic showers is at 38 degrees. When I've encountered these I've usually had to disengage the stop (ooh - what a risk taker!) to get a shower at the temperature I'd like. So it looks like I'm going to be needing water hotter than 35 with a commensurate reduction in flow, and therefore limited in the shower head I can actually pick if I want it to work properly.

Would something like this:

come under your idea of a "big soaker head"?

Why don't manufacturers (or maybe I mean retailers) publish these specs? If one did so they'd instantly become my first choice for what's looking to be quite a big purchase. All the web sites I've looked at are bare of any practical information about the products, and the bricks&mortar showroom I went to was no better, even to the point of the assistant denying that any number other than static pressure mattered at all.

Cheers,

Pete

[Pete Verdon]

Not exactly shafted, but yes, it does appear that my current boiler doesn't quite meet my showering aspirations. But then again, neither does my parents' conventional system, and at least mine doesn't fail in the "sorry, water's cold, you'll have to go to work without a shower" mode.

41.1kW, according to this: . However, that's a rather bigger boiler than I would want to install.

Pete

[The Natural Philosopher]

so either store the hot water preferably at pressure, or put up with a dinky shower.

Especially when someone turns the hot tap in the kitchen on ;-)

[Dave Plowman (News)]

I have a fast recovery cylinder and can get a warm shower only minutes after switching on from cold. As I discovered after coming back from holiday.