A major problem confronting anyone wishing to install a
shower in their home, either over a bath or in a separate
cubicle, is ensuring sufficient water pressure to operate the
shower satisfactorily. Most
people expect a shower to deliver a strong invigorating spray
rather than just a trickle of water.
All too often it is found that although water pressure is
adequate at bath and basin taps, once a shower is fitted, with the
spray head higher than other outlets, the pressure at the spray
head is totally inadequate. This is due to the spray head being too
close to the water level in the cold water storage tank.
Most showers will not perform unless there is a minimum height
of 1 metre between the spray head and the water level in the tank.
This is called the head of water. The higher the head the greater
the water pressure.
There are three ways to increase the pressure so that you obtain
the shower that you desire.
ONE is to raise the cold water storage tank
which feeds the hot water cylinder and the majority
of cold water outlets, thus increasing the head. This involves
building a platform in the loft and
raising the tank to achieve the extra head or pressure. Plumbing
pipework has to be extended
and making this a laborious job. In many lofts such a change
would not even be practical.
TWO is to fit an entirely independent
instantaneous shower heater, fed with cold water from the rising
main (an electric shower). The rising main will generally have
considerably greater pressure. The heater itself can limit
performance since the flow is controlled by the time it takes to
heat the water to the required temperature. Whenever someone runs
the tap in the kitchen, also fed from the rising main, or when the
cold water storage tank needs replenishing, water pressure will
THREE, and by far the best answer, is to
install a twin impeller shower booster pump. There are four common
types of twin impeller pumps available:
Plastic Twin Impeller Pumps 1.5 bar or 2 bar:
● Increases flow rate to up to 16 litres per minute (1.5 bar) /
25 litres per minute (2 bar)
● Designed for intermittent use - 20 minutes on / 40 minutes
● Transforms a new or existing shower into a power shower
● Fully automatic
● Increases the effective head by the equivalent of up to 12
metres (1.5 bar)/ 20 metres (2 bar)
● Quiet operation
High Performance Brass Twin Impeller Pumps 2 bar or 3
● Increases flow rate to up to 25 litres per minute (2 bar)/40
litres per min (3 bar)
● Designed for frequent/continuous use in domestic and light
● Increases the effective head by the equivalent of up to 20
metres (2 bar) / 30 metres (3 bar)
● Can power both a main bathroom and an en-suite
● Supplied with four high quality stainless steel braided
● Adjustable flow switch sensitivity
● Quiet operation
● Integral stainless steel inlet filters
The pumps are completely automatic once installed so you do not
have to switch them on and off when you decide to have a shower. As
soon as the controls to the shower are turned on and water flows
through the pipework, an in-built flow sensor operates, switching
on the pump. The only
requirement here is that the un-boosted flow rate from the
shower spray head, when at its highest point, must be a minimum of
0.5 litres of water per minute. This is normally the case when the
spray head at its highest point is not less than 225mm below the
water level in the storage tank supplying both the hot and cold
feeds.See Diagram A.
Twin impeller pumps are particularly suitable for installations
where access cannot be gained to pipework directly adjacent to the
shower, between the mixer and sprayhead, because it is embedded in
the walls, the situation in most homes. Connections are made to the
supply hot and cold pipework before it reaches the mixer valve. The
pumps can also be installed to boost supplies to other outlets in
the house, such as the bath and basin shown in Diagram
Before you Start
There are a few requirements which must be adhered to if the
Shower Booster Pump is to operate satisfactorily and safely.
The existing water supply to the shower should be of equal
pressure on the hot and cold side. This means that both hot and
cold water must come from the same source, a cold water storage
tank. Refer to Diagram A which indicates the pipe layout. In most
systems it is usual for the same cold water storage tank to feed
both the hot water cylinder and the cold taps, so pressure is
normally equal. The cold supply should not come directly from a
rising main since the pressure may fluctuate and will generally be
greater than the pressure from a cold water storage tank.
Pipework should be 22mm as far as possible to reduce flow
resistance. 22mm pipe is normally used for the supply from the cold
storage tank to cold water feed pipes and the feed pipe to the hot
water storage cylinder. Do not reduce to 15mm pipe until it becomes
The booster pump must always be sited with the pipe outlets
pointing vertically upwards.
To prevent air being drawn down the hot water storage cylinder
vent pipe and into the system, and to ensure that the shower has a
hot water supply that cannot be affected by water being drawn off
elsewhere, it is strongly recommend that the hot supply to the pump
is via a 'Surrey Flange' which is fitted to the top of the
cylinder.Diagram B. The Surrey Flange stocked by
Screwfix or Wickes and is supplied with full fitting
Flexible hoses must always be used to link both the incoming and
outgoing pipes to the pump. Some pump vibration is inevitable and
the flexible hoses help reduce the noise of such vibration and
damage to the pump.The High Performance Brass Pumps are supplied
with four high quality stainless steel braided hoses. You will
require four 22mm compression connectors for the hose standpipe
Positioning the Pump
Position the pump so that it can be easily reached for servicing
purposes this will save you time and trouble later on. The location
of the pump will depend, to some extent, on where hot and cold
pipes are accessible and also on whether the shower only is to
be served or other outlets are to be boosted as well. If, for
example, the pump is solely for use with the shower, the preferred
method is to have a dedicated supply. If, however, other outlets do
require boosting, the pump must be linked in to the main pipework
before the branches to those outlets.See Diagram C above.With these
factors in mind find a place for the pump where suitable
connections can be made, ideally in the bottom of the airing
cupboard. Under the bath or some similar location adjacent to the
shower area is acceptable but it should not be sited where it could
be splashed or touched. The pump sits on rubber 'buffer' pads to
reduce vibration noise, and must not be screwed down to the floor.
Use one end of the pump for the hot water, the other for the cold.
When fitting this pump remember that you will require two sets of
flexible pipe connectors. One flexible connector from each pair is
used to connect to the pump inlets, the other for the connection to
Pipe clips should not be used within 450mm of the pump, and
plastic clips are recommended elsewhere. metal pipe clips should be
avoided. Comprehensive fitting instructions are supplied with the
If using soldered joints, do not allow flux to come into contact
with plastic parts of the pump since the flux will cause corrosion
and, eventually, leaks.
A pump must be earthed. Electrical hazard will result if the
pump is not correctly earthed.
The pump must be connected to a 230 volt supply with a switched
spur fused at 5 amps. The switch must have a double pole
disconnection. The connecting flex must be double insulated 3 core
flex of 0.75mm2 area or more.
- Survey the current plumbing layout
- Decide on the best position for the pump
- Draw up a detailed shopping list and procure the bits.
- Run the pipe work to and from the pump
- Install electrical connections
- Commission and test the installation
Master Class - Extra bits to know about shower
Positive and Negative Head pumps
This is a term that you may have come across but
misunderstanding still exists to exactly what it all means.
In a nutshell, the difference between the two is determined by
whether the header tank is above or below the outlet point. If the
header tank is above you have a positive head. If it's below the
outlet you have a negative head.
In a gravity water system it goes without saying that water will
only travel in the direction of gravity - downward. For this reason
some people believe that if you take water down from the loft to a
ground floor hot water cylinder, then back up to a first floor
bathroom that water is indeed having to go up hill and that a
negative head scenario exists. In this example this would be an
incorrect conclusion. It is the relative position of the header
tank to the outlet point. If the header in the loft is higher than
the outlet point then a positive head exists even though the water
travelled down to the ground floor before going back up to the
If indeed the outlet is higher than the header tank and a
negative head exists you will require what's known as a negative
head set up. In a negative head scenario things kind of happen in
reverse. When you open your shower valve (or outlet - which could
be a tap) water would rather run backward down the pipe to the
header tank. SO... if you want your pump to activate automatically
it needs to be equipped with a different type of sensor. Negative
head pumps can usually be recognised by a canister that piggybacks
the pump. This is part of the sensing system - not needed on
positive head pumps.
Standard Pump (positive head required)
Negative Head Pump
Connecting a shower pump to a hot water
As mentioned, both the hot and cold feeds to a booster pump need
to be gravity pressure supplies. The cold water feed can either be
a dedicated cold supply direct from the header tank, or as is often
the case, by teeing into the cold water feed to the hot water
cylinder. Cold is simple enough. The hot water feed to the pump
needs a little more consideration.
The normal hot water draw-off point is typically at the top of a
hot water cylinder - right at the top, dead centre. If you simply
pull your hot water from this point you may end up with a
The reason: Hot water releases minute air bubbles. Ordinarily
these rise to the top of the cylinder and vent out through the
header tank in the loft. If you try taking water at the point where
the bubbles are leaving the cylinder you are likely to pull them
into the pump when it's running. This can cause a condition known
as cavitation. In a nutshell, a big bubble of air forms at the low
pressure zone ahead of the pump impellor. The condition can cause
damage to the pump and will almost certainly generate some weird
and wonderful noises - including squealing and banging!
1) If you intend to keep the present hot water cylinder you
should consider using either a 'Surrey' or 'Essex' flange. This
device screws into the top of the cylinder and creates two outlets.
One becomes the normal outlet/vent, the other (being the shower
take-off point) draws hot water from slightly lower in the
cylinder, hence allowing the bubbles to pass on by.
2) If you intend to change the cylinder for any reason then make
sure the new one has a dedicated shower take-off point. This will
do the job of a flange type device. Shower take-offs shouldn't make
the cylinder any more expensive, but you must ask for one to be
fitted as they are not normally included.
Water Storage - System Capacity.
You might really like the experience associated with a powerful
blast of water when taking a shower. Some people don't feel clean
unless they feel a layer of skin has been removed during the event!
But don't lose sight of how quickly you are emptying your water
storage vessels as you shower.
A boosted shower will empty your system quicker. The bigger and
more powerful the pump the quicker the system will empty. If you
simply add a pump to your existing system you run the risk of
potentially running it dry unless you do a few calculations. It is
actually quite difficult to be precise with this because of various
factors (how much water for example does your shower head
deliver?). You will need to make certain guesstimations. The amount
of water a shower pump will deliver will even be affected by how
big the holes are in the shower head, and how many there are! Some
how you need to calculate how big the header tank in the loft must
be in order to provide an average of 10 minutes shower time. Yes,
some people (especially teenagers) stand in the shower for longer,
so you must either make provision for this or re-educate users.
Some people find a timer on the show it use. Whatever you do and
however you choose to do it, make sure you don't run your pump dry
- this can cause it irreparable damage.
Shower pump construction.
The materials from which a pump is manufactured will invariably
influence the cost of the pump, but with good reason. Cheap shower
pumps rely heavily on plastics in their construction. Whilst there
is nothing wrong with plastics technology it happens to be a fact
that pumps made mainly from plastic don't last as long as their
more expensive counterparts. Pumps considered to be 'top end'
products tend to be constructed from metal - especially the
impellor housings that are often made of brass. It can often be a
false economy to buy a cheap pump as the brass-bodied models can
outlast them several times over.
Noisy shower pumps.
A noisy pump can annoy you or drive you to despair! Pumps
produce vibrations. This is a fact that cannot be ignored or
negated. If you are looking for a vibration-free silent booster
pump don't waste your time. Some pumps will vibrate more than
others. You can probably guess that cheap pumps utilising cheaper
materials and made with less refined manufacturing techniques are
likely to vibrate more than their more expensive cousins.
As mentioned, vibration is the culprit. Quality materials and
accurately machined components will minimise vibration and
therefore noise output but will not get rid of it entirely. It is
important to consider the transmission of vibration which is where
the noise comes from.
Manufacturers of the more expensive brands of pump recognise
this as a major issue. Pumps are therefore made from quality
materials such a brass, motors are often of the 'induction type'
that run more quietly and the foot upon which the pump stands is
designed to absorb vibration - minimising transmission into the
Choosing a site for your shower pump.
Apart from all the operational reasons that will determine the
most appropriate location for your pump, there is the issue of
vibration. Even the quietest most expensive pumps will vibrate when
in operation. It is therefore of paramount importance that you
consider well how and where to put your little noise generator.
Place a shower booster pump directly on a timber floor and you
might as well stand it on the sound box of a guitar. By it's hollow
nature the guitar sound box amplifies small vibrations from the
strings so you can hear them (by contrast a solid bodied electric
guitar needs an amplifier or it can't be heard). A hollow wooden
floor behaves in exactly the same way - amplifying vibrations.
Don't do it - the noise could drive you crazy!
Whenever possible you should choose a location and/or stand your
pump on materials where transmission of vibration is minimised. A
small pad stone, maybe some sort of sandwich including rubber or
polystyrene leaves might be considered a suitable way to insulate
yourself from vibrations. Experiment but make sure the pump will be
Don't be surprised if having ignored this advice you experience
If you need a pump repaired, replaced or installed.
Silver Saints, London's
Handyman Service, can help.
Use our 'Live Calendar' to BOOK ONLINE
Call: 0207 0999 199