Water pressure and the increased
demand on volume (flow) are important considerations if you are considering the
installation of a shower that incorporates multiple jets or shower
As you increase the number
of outlet points you increase the area over which your system pressure
and supply volume must divide itself. Put another way, as you increase
the number of outlets you must increase the supply pressure and flow
rate to maintain a status quo.
A pre-requisite for installations where
multiple outlets are incorporated is therefore good pressure and an
equally good flow potential. (*see note to accompany this point below)
As each installation and equipment used
will differ it is difficult to say exactly what your system should
provide. As a useful guide you should aim to have at least 2.5 bar.
Your attention is drawn to the fact
that everybody's expectation and desire from their shower will be
different. Some people feel disappointed unless they have been exposed
to a 'bruising' experience (also referred to a 'invigorating'!).
might find such brutal pressure quite unpleasant. One thing is for sure,
if you have just invested in a hydro massage shower pod and all you can
achieve is a dribble from the body jets you are going to be devastated.
Make sure you look into your system
capabilities before you spend any money. Some systems can be improved,
other can't. Here is a general guide to your possibilities.
1. Combination boilers - These are
generally OK for single outlet showers, what you might call the standard
type with a hose and handset only. Combi boilers are not good at
providing enough hot water for simultaneous demands, so they are totally
unsuitable for use with body jets, multiple heads or rain/deluge shower
heads. Don't allow
anybody to tell you otherwise.
2. Mains pressure hot water systems -
Providing you have decent mains pressure (2.5 + bar depending on what
you wish to operate) a mains pressure system with sufficient hot water
stored should work OK. Remember, everybody has a different definition of
a 'good shower' so keep this in mind when deciding how much water should
be stored (the longer the shower you typically enjoy the greater the
amount of hot water you should have available) and what pressure is functionally acceptable.
3. Gravity hot water systems - these
are notorious for providing poor (low) water pressure. But happily this
type of system can be boosted by installing a pump. [Only a system
with a cistern fed supply of stored water may have a pump added. It is
in contravention of Water Bye Laws to add a shower booster pump to a
system fed directly from the main (Combi Boiler, Unvented Cylinder or Thermal
Store). There's no point in trying to up
the performance of a combi.]
In many ways this makes the 'gravity
system' the most versatile. You can add a pump with a pressure rating that
suits both your shower setup and your shower expectations. Don't just
rush out and buy a pump though. You must appreciate what your changes to
the system will do.
*It is all too easy to focus on
achieving impressive shower performance. When you open your shower valve
you can marvel at all that water gushing out at good pressure. But take
a moment to consider where it is coming from and you will realise that
this high performance might not be sustainable. A booster pump can in
fact do it's job too well. As fast as the pump is delivering water it is
draining down your system. So much attention must be given to the amount
of hot and cold water on store. Yes, cold water storage is
most important. Remember, the cold water storage cistern (usually in
the loft) has double demand placed on it - after all, it is supplying
your hot water cylinder and it's your cold water supply to the
pump. So you must ensure you have plenty of cold water on store
otherwise you system will quickly run dry. Attention should also be
given to the size of the hot water cylinder. It is unlikely you will
want to stand in your all-singing and dancing shower and be blasted by cold water!
As a rule of thumb and a means to begin
your calculation you should make provision for about 10 minutes of
shower time. This gives you the ability to guesstimate the amount of hot
and cold water you will need to make available. To make the calculation
you need to establish roughly the amount of water your shower equipment
will deliver (the flow rate). So, for example....
Say your shower equipment will deliver a total
of 30 litres of hot/cold blended water water per minute. Multiply this
by 10 minutes.
30 litres x 10
minutes = 300 litres of cold water needed on store.
If we were to assume a 50/50 mix of
hot/cold water this would mean you would need at least 150 litres of hot
water available for your shower demand (although more would be
recommended). Equipment type and pump spec will
vary this approximation. The more jets, the more water you will inevitably
Never let your system run dry. You
could damage your pump. It is better to have more water on store than not
Just another thought, keep in mind that
pump output will remain the same. So don't loose sight of the fact that
switching between body jets to an single handset can change the
experience from good to brutal as the number of outlets reduces. It's a
compromise. A similar logic applies when using a single pump to supply
two showers. Remember you will divide the output from the pump when both
showers are used simultaneously.
Remember, we all differ in our
expectation of a 'good' shower. Some just want to get wet, others want
to feel like they've had a layer of skin blasted off them. It is
impossible to say what is right for everybody, so you must decide what
is right for you. The purpose of this article is simply to draw your
attention to the pitfalls.