9-07-01 Installation of ION exchange water softeners

June 2007
No 9-07-01
Water Regulations Advisory Scheme
Information for
Installation of Ion
Exchange Water Softeners
for Systems Supplying
Water for Domestic
Section 1 - Introduction
1. Introduction
In hard water areas water softeners can provide benefits
to the user in terms of reduced soap and detergent usage,
reduced scum deposits on sanitary ware and reduced energy
consumption due to absence of scale on water heating
In ion exchange water softening, the hard water flows
through a bed of ion exchange material (the resin) which
retains the calcium and magnesium ions that cause hardness
and replaces them in the softened water by sodium ions. The
ion exchange capacity of the resin is gradually used up and
when exhausted, it is regenerated by treatment with a strong
brine (common salt) solution, which is subsequently rinsed
out to waste.
This Information and Guidance Note (IGN) relates to the use
of ion exchange softeners for supplying water for domestic
purposes, which includes use of water for cooking, personal
washing and bathing, clothes washing and drinking, (but
see Section 8 regarding drinking water). Although principally
referring to softeners in domestic premises, it is applicable
to the same types of softener supplying water for domestic
purposes in non-domestic premises (e.g. an office canteen).
Where an ion exchange water softener is used for the
treatment of water for other than domestic purposes, this
IGN does not apply but regard should be had to its contents,
giving especial attention to the adequacy of backflow
prevention requirements which may be increased by the
uses of the soft water ‘downstream’ of the water softener.
The IGN does not apply to non ion exchange water softening
The IGN has been produced by WRAS on behalf of the public
Water Suppliers, in conjunction with the UK Water Treatment
Association (UKWTA) to provide guidance on the installation
of ion exchange water softeners in compliance with the
Water Fittings Regulations.
Section 2 - Water Fittings Regulations
Section 3 - Softener Construction
Section 4 - Water Efficiency
Section 5 -Backflow Protection
Section 6 -Connections/hoses
Section 7 - Waste water connections
Section 8 -Drinking water
Section 9 - Garden Supply
Section 10 -Installation Guidance
Section 11 -Maintenance
Section 12 -Further Information
2. The Water Fittings Regulations
4. Water efficiency
If water softeners receive water from the public water
supply, their installation and use in the UK is covered
by regulations and byelaws governing plumbing
systems. The Water Supply (Water Fittings) Regulations
1999 in England and Wales, (and the Scottish Water
Byelaws 2004 and Northern Ireland Water Regulations),
(collectively known as 'the regulations'), are intended
to prevent the waste, misuse, undue consumption
or contamination of public water supplies. All who
install water fittings, plumbing systems or water-using
appliances or use them have a legal duty to comply with
these regulations.
Water softeners must be designed, installed and
maintained to meet the regulations’ requirements.
Plumbing materials and fittings, including ion exchange
water softeners, must be of a suitable standard. The
regulations also require all appliances to have adequate
backflow protection to prevent contaminants entering
the plumbing system (see Section 6).
Regulation 5 of the Water Fittings Regulations requires
that the Water Supplier must be notified in advance
of the proposed installation of a water softener and
give its consent. Details of notification are given in the
WRAS leaflet ‘Information on Notification of Proposed
Plumbing Work’ available on the WRAS website
(see Section 12 Further Information).
It is important to install the softener in accordance with
the manufacturer’s instructions and this Guidance Note
is intended to explain why the specific requirements of
the installation instructions are necessary and to give
guidance on compliance with the Regulations.
The Regulations require that fittings shall not waste
or misuse water. The softener regeneration process
results in a discharge to waste of water containing
spent regenerant. Water softeners which exceed the
water consumption criterion set out in the Regulators’
Specification for water softeners (which specifies that
per regeneration cycle, the softener shall use no more
water than 18 times the volume of the resin) may be
considered by Water Suppliers to waste or unduly
consume water, in contravention of the Regulations.
Softeners manufactured to comply with BSEN 14743
'Water Conditioning Equipment inside Buildings –
Softeners' will satisfy this consumption requirement.
5. Backflow prevention
Backflow prevention for the supply pipe feeding the
connection to the softener is intended to prevent
softened water or, - in the event of a malfunction of
the softener – regenerant solution, flowing by backsyphonage or back pressure into the upstream part of
the domestic plumbing system or into the water supply
mains. Figure 1 illustrates how, if the mains pressure
drops, water from the premises can flow back into the
mains possibly contaminating the public mains supply.
3. Softener construction
Regulation 4 requires that 'every water fitting shall be of
an appropriate quality and standard and be suitable for
the circumstances in which it is used'.
Fig 1: Indication of backflow into a water main.
The level of backflow protection required is defined by
fluid categories given in Schedule 1 to the Regulations
and a backflow prevention device rated to at least the
same fluid category must be used for each backflow
risk. Domestic Ion exchange water softeners are in fluid
category 2. A type EA or EB single check valve is suitable
backflow protection for fluid category 2 and should
be fitted to the supply pipe immediately before the tee
feeding the softener (Figure 2).
Parts of a water softener which are in contact with water
which is intended for domestic purposes must not cause
contamination of the water. This requirement is met if
non-metallic components such as plastics, colourants,
elastomers, sealants, etc., including softener connection
hoses, comply with BS 6920:2000 (Suitability of nonmetallic products for use in contact with water intended
for human consumption with regard to their effect on the
quality of the water).
Components must also be capable of withstanding
without leakage or damage 1.5 times the maximum
water pressure to which they will be subjected.
The person who installs the softener and the people
using it are legally responsible for its compliance with
the Regulations. It is therefore essential that suitable
components are used and it is necessary to demonstrate
their compliance. It is recommended that the products
and materials used are listed in the on-line WRAS Water
Fittings and Materials Directory, as these have been
assessed on behalf of the Water Suppliers as meeting
the Fittings Regulations providing they are installed in
accordance with the specified conditions (see Section 12
Further Information). .
Fig 2: Bypass, connections and check valve
6. Connections/hoses
The softener requires four plumbing connections: the
hard water inlet, the soft water outlet, the drain and the
overflow. Some softeners also require connection to the
electrical supply to power the electronics for
the automatic regeneration system.
The connections between the supply pipe and the
softener are normally made in flexible pipe to enable the
softener to be moved for servicing. Where the softener
is located in a confined space that would impede
maintenance, the length of flexible connections should
be cut to allow the unit to be moved (after closing the
bypass valves) to a position such that maintenance
access is acceptable. The hose used must be suitable
for drinking water applications – dishwasher, washing
machine or garden hoses are not suitable.
A bypass should be provided for the softener so that
the unit can be isolated for maintenance purposes. This
should comprise, as a minimum, isolation valves on
the inlet and outlet of the softener and a bypass valve
between the inlet and outlet T-pieces to and from the
softener (Fig. 2).
maximum drainage capacity and the bore should not be
reduced by alternative tube or any connector that may be
needed. Where flexible hose is used, care must be taken
to minimise the length of flexible hose and it must be
routed and supported such that any movement during
maintenance cannot cause it to kink.
8. Drinking water tap
Advice from the World Health Organisation and the
Department of Health about drinking softened water
leads Water Suppliers to recommend that where water in
premises is to be softened, a separate unsoftened water
tap should be provided for drinking water. This should
preferably be at the kitchen sink but alternative positions
such as at a utility room sink can also be acceptable.
The separate unsoftened drinking water tap should be
connected into the supply pipe upstream (before) of the
bypass to the softener and run directly to the tap (Fig 4).
7. Wastewater connections
Air gap to drain
The drain is connected to the drainage system which is a
backflow risk in fluid category 5. Clearly the prevention
of possible backflow of sewage into the water supply
is of paramount importance. The requirement for this
connection is therefore an air gap which must satisfy the
Regulator’s Specification. (Figure 3).
Fig 4: Connection for drinking tap upstream of the water softener.
The Regulations require that 'All premises supplied with
water for domestic purposes shall have at least one
tap conveniently situated for the drawing of drinking
water'. Drinking water must comply with the Water
Supply (Water Quality) Regulations 2000, which stipulate
a maximum limit of 200 mg/l (milligrams per litre) for
sodium. The Department of Health recommends that
this sodium limit should not be exceeded for infant feed
preparation and for those individuals on a medically
supervised low-sodium diet.
Fig 3: Connection to drainage system via an air gap
The drain connection from the softener can be via a
waste pipe upstand but it must incorporate an air gap
to drain, which is designed to provide an unobstructed
gap between the outlet from the softener and the drain
connection, as shown in Figure 3. Thus, if there is a
blockage or back-pressure in the drain, water from the
drain cannot be drawn into the softener if the water
supply pressure fails at the same time.
It requires a minimum unobstructed air gap of 20 mm (or
twice the diameter of the drain tube from the softener–
whichever is the greater).
The overflow from the brine tank should be connected
using pipe with a minimum 15mm diameter with a
continuous free fall through an outside wall to a location
that will be readily evident to warn the consumer of
an overflow fault condition. The outlet should not
be directed into a drain or gulley in such a way that
immediate evidence of overflow condition is obscured to
the user. It should be kept as short as possible to allow
The provision of an unsoftened drinking water tap is
essential where the hardness of the public supply and its
sodium content as supplied would result in the softened
water exceeding 200 mg/l sodium limit.
For ion exchange softened water, this limit will be
exceeded where the water is extremely hard, i.e. above
425 milligrams per litre as CaCO3 (assuming zero
sodium in the public supply).
Fig 5: Sodium content resulting from softening water of a given hardness
(with no allowance for sodium content of the water as supplied)
Before installing the water softener, installers must check
by asking the local water supplier the level of water
hardness and sodium in the area, so that the sodium
level after softening will not exceed the 200 milligrams
per litre value, and advise the customer accordingly.
Supply Pressure
Before installing a softener the local water supplier
should be contacted for information relating to the
normal operating pressure for a supply area to confirm
that it is neither too high nor too low when checked
against the manufacturer’s instructions. If the pressure
is too low it may affect the functionality of the softener;
if the pressure is too high it may cause leakage or
premature failure and a pressure reducing valve
may be required.
9. Garden supply
For reasons of salt consumption and water wastage, it is
obviously preferable for unsoftened water to be used for
outdoor purposes. It is recommended, for convenience
and economy, that the garden tap is connected to the
hard water supply, upstream of the softener connection.
Where this is not possible due to plumbing complexity,
an option is for the consumer to bypass the softener (see
bypass above) when using water for garden purposes.
Manufacturers of water softeners should include
written instructions giving clear advice on routine
checks to be made on operation of the system to ensure
continuous and effective function. Installers should
ensure the operating instructions are given to the users.
Inadvertent or intentional isolation of the softener for
extended periods should be avoided and reinstatement
of operation after a period of several days’ interruption
should be preceded by manual regeneration of the unit.
In the case of a twin cylinder unit, both cylinders should
be regenerated sequentially.
10.Installation guidance
Location of the softener
Proper siting of the softener is vital. It must be
positioned so that the user can readily access the
unit in order to check the salt level and replenish it as
necessary. Access to the bypass valves is also essential.
There should be sufficient clearance between the top of
the softener and its enclosure to be able to operate the
manual regeneration function.
The ideal location is under the kitchen sink, because
it will be regularly visible to the customer for checking
salt level, and installation of the separate tap will be
simpler. However, proximity to the incoming supply pipe
(if this is not under the sink) is also important in order to
minimise long pipe runs to the softener connections.
To minimise any temperature rise in cold water supply,
the softener should be located away from any sources of
heat, such as oven, boiler, hot water cylinder, etc. Also
close proximity to hot water pipes should be avoided.
Where this is not possible, suitable thermal insulation
should be applied to the hot and cold pipes as necessary.
Any cold pipe runs should be beneath, not above, any
hot water pipes that are near. All pipe runs should be
kept as short as possible.
12.Further information
Further information and advice can be found in the
following publications:
BS 6700:2006 Specification for design, installation,
testing and maintenance of services supplying water for
domestic use within buildings and their curtilages.
The Water Regulations Guide, available from WRAS,
contains the Regulations and technical Schedules,
the Government Guidance and the Water Industry’s
recommendations for complying with the Regulations.
The Water Fittings and Materials Directory lists products
which have been tested and approved by the WRAS for
their compliance with the Regulations (available on the
WRAS website www.wras.co.uk/products).
Information and Guidance Notes are available on the
WRAS website (www.wras.co.uk).
Softened Drinking Water Booklet available from
UKWTA (info@UKWTA.org)
For further copies of this Information and Guidance
Note and technical information may be obtained from
WRAS website or by contacting WRAS at:
For installation outdoors, or in an unheated outhouse,
protection against freezing is essential to prevent
damage to the unit and consequential water loss.
If as part of the installation the existing pipework is
interrupted, particularly by use of a non-metallic bypass
set, the earth bonding should be checked by a suitablyqualified person to maintain safe electrical earthing,
although the supply pipe should never be relied upon
exclusively for this purpose.
Plumbing route
As with any plumbing work, pipe runs should be kept
as short as possible to minimise pressure loss and
stagnation. Similarly, bends and fittings should be
minimised to reduce pressure loss. The route will be
determined primarily by the location of the softener, but
the pipe route for the hard water drinking tap will also
need careful planning to avoid unnecessary disruption to
the existing premises.
Water Regulations Advisory Scheme
Unit 30, Fern Close, Pen-y-Fan Industrial Estate,
Oakdale, Gwent NP11 3EH
Tel: 01495 248454. Fax: 01495 249234
E-mail: info@wras.co.uk
UK Water Treatment Association,
Loughborough Innovation Centre, Loughborough
University, Loughborough, Leicestershire LE11 3TU
Tel/Fax: 01509 215000
E-mail: info@ukwta.org
June 2007 first impression. Isca/HSW
Download PDF