Requirements for Cold Water Storage Cisterns

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Requirements for Cold WaterStorage Cisterns
A presentationbyDouglas WebleyandDebra
Taylor-Croather
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Requirements for Cold Water Storage Cisterns

• Introduction
• The aims of this slideshow are to
• Introduce the regulations for the installation of
  cold water cisterns
• The objectives of this content are to ensure that
  students are aware of
• The general requirements for storage cisterns
• The installation requirements for storage
  cisterns
• The Requirements for Positioning Storage Cisterns
• Water inlet requirements for storage cisterns
• Water outlet requirements for storage cisterns
• Warning and overflow requirements for storage
  cisterns
• Requirements for coupling storage cisterns
• Commissioning storage cisterns

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The general requirements for storage cisterns
When it is required to store cold water for use
as a supply for an indirect system of cold water,
or for the feed to a system of dhw, the water is
stored in a cistern, usually in the loft space.
The cistern should have a close fitting lid
that prevents any light or insects from entering
the cistern but it must not be air tight. To
ensure of this all vents, warning pipes and
overflows should be screened with a corrosion
resistant mesh with a maximum opening size of
0.65 millimeters. An access cover should be
provided if the tank volume is greater than 1000
litres. This is to ensure that maintenance and
cleansing can be performed without completely
removing the cistern cover.
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The general requirements for storage cisterns
Some of the possible consequences of not
following the general requirements as set out in
regulation 16 are that the water stored can
become contaminated by insects that gain access
via the open lid or by crawling up the unscreened
warning or overflow pipe, insect larva that
require water to complete their lifecycle such as
mosquitoes. Animal waste from birds or rodents
that can access the area around the storage
cistern, the bodies of birds or rodents that have
got trapped in the cistern and died.
Any of the above problems can cause contamination
of the water supply and are a potential health
hazard to those using the water supplied from the
cistern.
The above diagram shows a correctly installed
water storage cistern
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The general requirements for storage cisterns
The storage cistern should have a minimum
capacity of 100 litres. If the cistern is also to
act as a feed cistern for a hot water supply, it
must have a minimum capacity of 230 litres. If
the cistern is also to act as a feed cistern for
a hot water supply it should have a minimum
capacity of 230 litres. For more information on
the general requirements see section G16.13 of
the Water Regulations Guide.
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The installation requirements for storage cisterns
The storage cistern would need to be adequately
supported to prevent distortion or damage to the
cistern and pipe work. Water is very heavy,1
Litre weights 1kg. 1 cubic Metre weighs 1000 kg.
From this we can appreciate that the support for
the cistern would have to be substantial.
Normally we would try and position the base for
the cistern over a load bearing wall in the roof
space.
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The installation requirements for storage cisterns
Insulation is not included beneath the cistern
and if it is present at installation should be
removed. For domestic installations the support
for the cistern will be made of moisture
resistant close boards covering the total area of
the base of the cistern.
The close board is fully supported across the
width with three pieces of wood measuring at
least seventy five Millimetres by fifty
Millimetres that are no further apart than three
hundred and fifty Millimetres. All holes made in
a plastic cisterns should be made with a hole
saw. It is essential that you remove any plastic
that may fall inside the tank during any cutting
operations performed on the cistern.
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The Requirements for Positioning Storage Cisterns
The requirements for the positioning of and
access to cisterns depend on the volume of the
cistern involved.
Positioning cisterns of 1000 litres and below
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The Requirements for Positioning Storage Cisterns
The requirements for the positioning of and
access to cisterns depend on the volume of the
cistern involved.
Positioning cisterns of 1000 litres and above
For more information on the positioning
requirements see section G16.14 of the Water
Regulations Guide.
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Water inlet requirements for storage cisterns
The inlet requirements state that all cisterns
will be fitted with an adjustable water inlet
control device. These devices are usually float
operated and must conform to British Standard
1212.

• Float Valves
• The British Standard defines four types of float
  operated valves that are suitable for use in cold
  water cisterns
• Part one - Portsmouth type
• Part two - Brass Diaphragm type
• Part three - Plastic Diaphragm type
• Part four - Diaphragm Equilibrium type

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Water inlet requirements for storage cisterns
The diagram below shows a cross section of a
common float valve. The diaphragm indicated can
be made of brass (BS1212 Part 2) or plastic
(BS1212 Part 3).The adjustment screw allows for
the valve to set at the correct water level.
It is important to note that British Standard
1212 only covers valves up to 2 inches in size.
Any float valve fitted that exceeds this size
must authorised by one of the following
bodies 1 - Water Regulations Advisory Service 2
- Water Fittings and Materials Directory 3 - Your
Local Water Provider
For more information on inlets to cisterns see
section G16.4 of the Water Regulations Guide.
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Water outlet requirements for storage cisterns
Outlets from cistern include indirect cold water
feeds, cold supply to hot water systems such as
immersion heaters and central heating
systems.The diagram shows the positioning of
cold water distribution and hot water system feed
pipes. It is recommended that the cold water feed
pipe be taken from the bottom of the cistern.
This is to prevent the build up of sediment on
the bottom of the tank alternatively the cold
water feed can be located on the side of the
cistern.
Hot water system feed pipes must always be
positioned above cold water system feed pipe.
The distance between the cold water feed outlet
and the hot water system feed, indicated by
arrows A and B on the diagram, should be not less
than the internal diameter of the outlet pipe
being used.
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Water outlet requirements for storage cisterns
Prevention of Stagnation Correctly positioned
outlet pipes can help to prevent stagnation of
the water held in a cistern by ensuring a through
flow of water. If there is only one outlet
fitted then it must be positioned on the opposite
side of the cistern to the water inlet valve.
If there are two outlets fitted they should be
positioned on opposite sides of the cistern with
one higher than the other . The higher outlet
should be on the opposite side of the cistern
from the water inlet valve. This arrangement
ensures circulation of the water within the
cistern which in turn helps to prevent
stagnation..
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Warning and overflow requirements for storage
cisterns
Cisterns Under Five Thousand Litres A warning
pipe has a smaller diameter than an overflow pipe
and is intended to act as a warning of imminent
overflow. An overflow pipe has a larger diameter
than a warning pipe and should be able to carry
the excess water that would be present if the
inlet valve fails completely and lets in the
maximum amount of water possible. This should
ensure that the inlet valve will never become
submerged and the cistern will not flood the area
in which it is situated. Warning and overflow
pipes should run to a point outside of the
building that is clearly visible and below the
level of the storage cistern. Warning pipes
should be situated below the overflow pipe so it
is obvious which pipe is which. Overflow and
warning outlet requirements for cold water
cisterns vary with the storage volume of the
cistern being installed .
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Warning and Overflow requirements for storage
cisterns
Cisterns Below 1000 litres Cisterns below one
thousand litres capacity require a single
combined warning and overflow pipe. The bottom of
the combined warning and overflow pipe should be
a minimum of twenty five Millimetres above the
water level of the cistern.
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Warning and Overflow requirements for storage
cisterns
Cisterns above 1000 litres and below 5000
litres Cisterns above one thousand litres
capacity require separate warning and overflow
pipes. The bottom of the warning pipe should be
a minimum of twenty five Millimetres above the
water level of the cistern.
The bottom of the overflow pipe should be a
minimum of twenty five Millimetres above the
bottom of the warning pipe.
For more information on warning and overflow
pipes see section G16.8 of the Water Regulations
Guide.
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Warning and Overflow requirements for storage
cisterns
Cisterns Over Five Thousand Litres Cold water
storage cisterns with a volume greater than five
thousand litres require warning systems that
indicate when problems develop. Cisterns above
five thousand and below ten thousand litres
capacity require a single overflow pipe.
The bottom of the overflow pipe should be a
minimum of fifty Millimetres above the water
level. Cisterns of this capacity should also be
fitted with a visual water level indicator. This
system should have a sensor that is mounted
twenty five Millimetres above the maximum water
level of the cistern.
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Warning and Overflow requirements for storage
cisterns
Cisterns Over Ten Thousand Litres Cisterns above
ten thousand litres capacity also require a
single overflow pipe. The bottom of the overflow
pipe should be a minimum of fifty Millimetres
above the water level. Cisterns of this capacity
should also be fitted with a visual or audible
alarm.
This system should have a sensor that activates
the alarm when the water comes within fifty
Millimetres of the bottom of the overflow pipe.
For more information on warning and overflow
pipes see section G16.8 of the Water Regulations
Guide.
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Requirements for Coupling Storage Cisterns
It is sometimes desirable to couple two storage
cisterns together rather than have one large
storage cistern. This can happen in larger scale
installations or where a lack of space limits the
size of cistern that can be used and there is a
need for storing a larger volume of cold water
than one small cistern could hold.
Another benefit of using two coupled cisterns is
that maintenance can be carried out on one
cistern without having to interrupt the water
supply to the rest of the system.
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Requirements for Coupling Storage Cisterns
The diagram above shows two cisterns coupled in
such a way that either could be isolated from the
other. This arrangement is not usual in domestic
situations.
The diagram shows the more common coupling
arrangement found in domestic dwellings where
coupled cisterns have the water inlet in one
cistern and the water outlet taken from the
other. This is to aid water circulation and
prevent the possibility of stagnation.
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Commissioning Cold Water Storage Cisterns
Once the installation of a cold water storage
tank is complete the system must be commissioned
before being cleared for usage. Often not enough
time is allocated for this task or it gets
overlooked completely but it is important to
ensure that the job has been finished and that
there are no loose connections or anything else
that could cause problems. Water can cause major
damage that is expensive to correct. Before
commissioning cisterns should go through the
following checks Visual Inspection Check the
cistern visually, is the inlet valve fitted, are
the outlet pipes fitted, are the warning and / or
overflow pipes connected correctly, is the
cistern situated correctly, does it have adequate
support, is the lid fitted correctly, are the air
vents, warning and overflow pipes screened to
prevent insects gaining entry to the cistern, if
it is a large cistern is there a warning gauge or
alarm fitted, is the cistern sufficiently
insulated.
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Commissioning Cold Water Storage Cisterns
Soundness Testing Check that all connections to
the cistern water inlet and outlets, warning and
overflow pipes have been tightened and are
watertight. Check that any joints in the pipe
work to and from the cistern are water tight and
that the pipes are insulated. Flushing and
Disinfecting When ever any work is carried out
on water supply systems the apparatus and pipe
work involved should be flushed and disinfected
in accordance with British Standard 6700 clause
3.1.10.1 For small installations, a single
dwelling for example, a visual inspection and
removal of any debris from the cistern and
flushing of the pipe work with clean water to
remove any flux remaining in the pipes would be
sufficient. For blocks of flats and larger
buildings then full disinfection as described in
British Standard 6700 would be required
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Commissioning Cold Water Storage Cisterns
Performance Testing It is important to ensure
that the cistern can meeting the demands that
will placed upon it. To these ends the cistern
should be tested to full capacity to ensure that
there is no individual system that gets starved
of water when demand on the cistern is at is
highest. This is important because if hot water
systems do not get sufficient water then scalding
can occur due to the water getting over heated.
Final Checks and Handover Once the above
tests have been completed it is a good idea to
give the system one last check over to see if any
problems have come to light during the
tests. You should now be confident to hand over
the installation to the customer.
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Acknowledgements

• Written and produced at South Birmingham College
• The Centre for the Built Environment
• Textual content written by Douglas Welby and
  Debra Taylor-Croather with additional content by
  Christopher Poole
• E-Learning Content Development Unit
• Web Development by Christopher Poole and Roland
  Douglas
• All drawings by Christopher Poole
• Distribution
• Distributed by the Learning and Skills
  Development Agency and the National Learning
  Network as part of Project Q 2005

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Important Information
Please Note While every attempt has been made
to ensure that the contents of this learning
object are correct and follow the guidelines as
laid down in the Water Regulations Guide second
edition South Birmingham College cannot be held
responsible for any loss or damage caused by
reliance on these materials. All works should
carried out by fully qualified persons.