I have recently had a new thermostatic mixer shower installed by my
friendly local plumber. It is a Sfera drop plus
(http://www.tlc-direct.co.uk/Products/SHSFTPLUS.html ). However, the
output is lukewarm at best and opening another tap in the house causes
the shower temperature to plunge!!
I have had a new 30kw condensing boiler fitted and all other taps in
the house are producing lots of hot water. Does anyone have any idea
how I can improve this? Do I have a dodgy thermostatic cartridge?
Thanks in advance for your help
The plumber has tried switching the feeds but the shower just runs cold.
Looks like I have got a dodgy shower... does anyone else have
experience of this model (not one of the major brands, I know!!!).
On Wed, 20 Sep 2006 18:08:45 +0100, "news.tiscali.co.uk"
Sorry I didn't get it for you. Reason I gave that answer was I put
mine in 3 weeks ago and got exactly what you had for the reason I
gave. Changing the feeds produced a superb shower.
(Now overused by the whole household.)
Best of luck.
I'm no plumer and this is based on advice I received when I opted for a
combi system ten years ago. As the shower is fed from the boiler it's
relies on the amount of water the boiler can produce (measured in litres
per min). Although this might behot and sufficient for filling a sink
or bath it's prob not enough for a decent shower.
My combi boiler is 32kw and produces 13 odd litres per min, if I use the
mixer head on the bath tap the effect is fine for rinsing my hair but
would not make an impressive shower! Your 30kw boiler will prob put out
a little less insufficient for a good shower IMO.
As it is fed from the boiler, any additional hot water demand will
affect the amount of hot water supplied to your shower though I would
have thought the thermostat would reduce the amount of cold water used
to balance the drop in the hot water. There might be a small brief temp
fluctuation but more noticable would be the reduction in water output
from the shower.
It does say 'Ideal for use with a Combi Boiler' but probably one with a
much higher flow rate. I had a look at the technical download not much
help as it was in italian and looked like fitting instructions rather
The shower does look pretty though.
Since my first post I readjusted the spindle "set point" and the shower
was more than hot enough with a really good flow rate. My plumber
seems convinced that we have more than enough pressure to drive this
The problem remains that the shower is not very controllable - and
opening a tap elsewhere causes the shower temperature to drop
drastically. I am thinking that this is a problem with the
thermostatic cartridge. My plumber has returned today so I will see if
he has any bright ideas otherwise I will try and get a new cartridge
out of the manufacturers.
Thanks again for the advice everyone, your help is greatly appreciated.
I will let you know how I get on...
This can happen if the valve does not contain a pressure balancing
mechanism. Such a system is absolutely essential to a mains pressure shower,
such as one fed from a combi. You can get external add on valves if your
shower valve does not incorporate one.
Obiviously, your combi can only supply a certain amount of hot water, so if
you turn on a hot tap elsewhere and use more than you can produce, it won't
work. However, the pressure balancing valve will help in other
circumstances, such as drawing a small amount of water elsewhere, or turning
on a cold tap (or flushing a toilet).
Thanks for the info Christian
Right, this shower is driving me nuts now!! I have just tested the
shower again and now it seems to have improved - not perfect but a
The shower is chucking out loads of hot water at a really good flow rate
- no complaints there. Yesterday, if a hot tap was turned on elsewhere,
the shower would go really cold. Today, the temperature is (more or
less) holding at a reduced flow rate. Yesterday, the temperature
control had little effect - today, the temperature is much more
This is all very odd.... Could it be that the shower needed a bit of a
"run-in" period??? Perhaps a bit of grit has been flushed out of the
cartridge??? I really don't know what to make of all this - does anyone
have an explanation.
Cheers again for your suggestions
Christian McArdle wrote:
There was a thread on Aqualisa showers recently. Different cartridges
for each type of hot water supply. Yours may be the same but in
My shower cartridge (storage cistern type) only controls at a highish
flow rate. If yours is similar you may exceed your hot water supply. I
suppose you could try a shower head with smaller jets.
If the plumber chose the unit, knowing your boiler capacity, I think it
is his problem.
Well, I have just had my morning shower so I thought that I would report
back!!! The shower performance seems to be pretty good now with the
temperature remaining pretty stable even when a cold tap is opened.
When a hot tap is opened the temp does drop (5 degrees or so) -
presumably because the boiler output cannot match the demand.
Is this normal or would I get better thermostatic performance from a
different model? This shower requires pressure of 2 bar to drive it - I
have noticed that some showers can run off 0.3 bar.
Thanks once again for all the advice.
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