58
TECHNICAL
Selecting the correct
taps or mixers
Patrick Gordon
Patrick started in the
plumbing retail business
in 1985 with the Boumat
Group. In 2000, he moved
from retail to manufacturing
and joined Cobra Watertech
as a call centre administrator.
He rapidly moved up in the
company and served as
product support manager
/ product development
manager and in 2005, he
was asked to take over the
product support department
nationally. He then qualified
as a facilitator and assessor.
When LIXIL Africa was
formed and they had to train
all the companies — Grohe,
Cobra, Isca, Vaal, Plexicor
and Libra — the training
department was expanded.
Research shows that most people will only redo or
upgrade their bathrooms once in their lifetime. This
highlights the need for selecting the correct product to
suit your individual needs.
By Patrick Gordon
So, what are some of the deciding factors that need
to be considered when making this selection? user comfort. The actual installation will not be influential
on this selection.
WATER PRESSURE
Why would the water pressure be the first consideration?
One of the main things that we automatically expect
from a tap/mixer is user comfort — we need to enjoy
the experience. If the flow pressure in the fixture is too
low, the user experience will be poor. So how do we
retain the user comfort in a low-pressure installation?
Friction loss happens due to small porting in the fitting
and the resulting high velocity. To reduce the friction
loss, we need to reduce the speed of the water in the
fitting and the only way to do this is to have a fitting with
large waterways. To put that in other words: you need a
heavy-pattern tap/mixer. With most manufacturers, only
light-pattern taps are produced. This is due to the fact
that the highest demand in modern society is for high-
pressure installations. FUNCTIONALITY
Here we need to keep in mind what the purpose and the
design of an item is. We would not use a gate valve to
control the water in our shower.
WATER QUALITY
Water quality is of utmost importance. The trendiest style
is to use single-lever mixers. These mixers make use of
ceramic discs to regulate the flow and mix of the water.
If the water quality is below standard, the suspended
solids in the water will damage these ceramic discs and
the mixer will leak. Screw-down taps/mixers use rubber
components on a metallic seat to control the flow of the
water. This system is less susceptible to damage from
suspended solids than single-lever mixers. If you still
want to use single-lever mixers, you will have to improve
the quality of the water by installing an in-line strainer.
A strainer needs to be fitted to all systems as per SANS
10252 Part 1, where it states that the complete system
should be protected from the ingress of dirt to the size
of 710µ.
STYLE
Style is an obvious criterion in most selections, but this is
based on personal likes and dislikes as well as perceived
May 2018 Volume 24 I Number 3
DESIGN
It is vital to keep in mind what we want the unit to do and
more importantly, what the manufacturer designed the
unit to do. Let us look at a couple of examples.
A demand tap is a terminal fitting and we would mount
it on a basin. But what is a demand tap designed to do?
Just as the name says, it delivers water on demand.
Would you use it on a basin for people to wash their
hands? No, because you cannot wash your hands
while keeping the tap depressed with one hand. Here
we would rather use a metering tap that continues to
dispense water for a set period after you take your hand
off the tap. This would then be suitable for washing your
hands but would still close automatically without any
user interaction.
A gate valve is designed to work as an isolating
mechanism and will not work correctly if it is used as a
terminal fitting. There are some taps that are designed to
work at very low pressures. A typical example of such a
unit is a tap that is used on a water tank. These normally
make use of a tapered, metal to metal seal, to shut the
water. Something that is on everybody’s mind these
days is water saving. This must also form part of your
consideration.
Most showers have a flow-restricted feed so that they
do not exceed 9ℓ/m flow. Before deciding on any unit,
make sure that they use a ‘pressure compensating flow
restrictor’, as these are not affected by pressure when
delivering the maximum flow.