1. Cisterns and Insulation
Cold Water
Cisterns and Insulation

2. Objectives
Identify key types and method operation of float operated valves used in cisterns
Detail the requirements for the installation of a cold water storage cistern for domestic purposes
Outline the requirements for insulating hot/cold water systems pipework/components
Identify the reasons for applying insulation – frost protection and prevention of undue warming
Barry Spick

3. Cisterns
A cistern is an open topped vessel subject only to atmospheric pressure. It is designed to hold a supply of cold water and should be fixed as high as possible to give adequate pressure flow.
Storage cistern – this is designed to hold a reserve of water to supply cold water to the various appliances fitted to the system
Feed cistern – This is designed to hold a reserve of water for the hot water system only
Combined storage and feed cistern – This type of cistern should be large enough to supply cold water to appliances and the hot water system
Barry Spick

4. Requirements
Every inlet control device shall be securely fixed, and when fixed to the cistern, shall be braced so as not to distort the cistern, and so affect the water level at which it closes.
Fitted with service valves on inlet and outlet pipes
Fitted with screened warning/overflow pipes
Covered to exclude light or insects
Insulated to prevent heat loss and undue warming
Installed so that risk of contamination is minimised
Arranged so that water can be circulated to prevent stagnation
Supported to avoid distortion or damage leading to leaks
Readily accessible for maintaining or cleaning
Water regulations require that cold water systems should not exceed 200C, but realise during hot months it can rise
Must not rise above 250C
Barry Spick

5. Requirements cont’d
Using insulation on components means that as well as protecting from the cold the insulation also protects from the heat.
Must have 350mm minimum access above cistern lid
Barry Spick

6. Materials used for cisterns
Older cisterns mainly made from galvanised LCS
You may come across these when doing maintenance jobs
What other materials are they made from?
Polyethylene
Polypropylene
Polyvinyl chloride
Also made from fibreglass
Cisterns made from these are?
Light
Strong
Hygienic
Resistant to corrosion
Flexible
Can be fabricated in a variety of shapes and sizes
Barry Spick

7. Supports
Because of their flexibility plastic cisterns require a full base support
View movie
If cistern is in insulated roof space ensure that insulation is not placed under the cistern. Why?
Cut holes in cistern with hole cutter, why?
Use plastic washers to seal joints to cistern, why?
DO NOT use jointing compound, why?
Causes the plastic to break down
Barry Spick

8. Barry Spick 8 8

9. Barry Spick 9 9

10. Connections and Control Valves
Water regs require that a pipe supplying water to a storage cistern be fitted with an:
Effective adjustable shut off device
For most domestic situations these are:
Float operated valves to BS1212 parts 1 to 4
Part 1 = Portsmouth type
Part 2 = Diaphragm valve made of brass
Part 3 = Diaphragm valve made of plastic
Barry Spick

11. Connections and Control Valves
Part 4 = diaphragm equilibrium float valves
Used for wc cisterns
Part 1 valves are not commonly used nowadays
Do not conform to the water regulations for backflow prevention
Can still be found when you do maintenance on existing cisterns.
Barry Spick

12. Connections and Control Valves
Part 4 = diaphragm equilibrium float valves
Used for wc cisterns
Part 1 valves are not commonly used nowadays
Do not conform to the water regulations for backflow prevention
Can still be found when you do maintenance on existing cisterns.
Barry Spick

13. Servicing valves Inlet pipes to cisterns must have
Servicing valve fitted immediately before connection to the cistern where practicable
Valve installed normally ‘spherical type plug valve’
Outlet pipes such as cold feed and distribution pipes
Should be fitted with servicing valves
These should be
‘Gate valve type’
Barry Spick

14. Connections to cistern
Outlet pipes should be connected as low as possible to the cistern
Water regulations are moving towards connecting the outlets to:
The bottom of the cistern rather than the side
Barry Spick

15. Connections to cisterns
Not less than 25mm
Cold water supply to hot water outlets to be taken from side of cistern above the outlet serving cold water distributing pipes WP
Shut off level
Alternative for cold water distributing pipe to appliances A B
Bottom outlet from cistern recommended where practical to reduce sediment in bottom of cistern
‘A’ or ‘B’ to be not less than internal diameter of outlet of cold water distributing pipe
Next
Barry Spick

16. Overflow pipes and warning pipes
Is used to discharge water where it will not damage the building
Warning pipe:
Is an overflow pipe used to give warning that a cistern is overflowing to the occupiers
Minimum dia of pipe to be 19mm
25mm
50mm
Warning pipe
Barry Spick

17. Overflow pipes and warning pipes
For cisterns up to 1000 ltrs
Must be fitted with a combined warning/overflow pipe
For cisterns between 1000 & 5000 ltrs
Both warning pipe and overflow pipe are fitted
If float valve becomes defective:
Warning pipe should be capable of removing excess water
Warning pipe should be continuous from cistern to point of discharge
Should discharge where they will be noticed
Should be fitted with a screened filter to exclude insects
Barry Spick

18. Roof spaces Water regulations require
That cold water systems do not exceed 250C
Insulation to be provided in hot places where cold water pipework passes through
Connecting two cisterns together
Avoid stagnation contamination
Ensure there is circulation of water from inlet to outlet
Screened overflow
In same cistern as float
valve
Service valve
28mm connecting pipe
Cold distribution pipe
Barry Spick

19. End of Cisterns
Barry Spick

20. Frost Protection What happens when water freezes:
It expands by approx 10%
What occurs when water freezes in a pipe?
An ice plug forms
The only place for the expansion to go is by splitting the pipe
When the ice thaws this is when we notice the burst pipe
Frost protection is dealt with in both the water regs and BS 6700
Barry Spick

21. Frost Protection (below ground pipework)
Min depth 750mm
Where it enters the building through solid floor
Must be ducted
Sealed at both ends to prevent moisture entering
When it enters through a suspended floor
It should be ducted
Duct ends to be sealed
Insulated to a depth of 750mm below ground level
Barry Spick

22. External applications
Where a standpipe is fitted
requires adequate protection
This picture shows a typical installation
The drain valve is fitted below the bib tap
This will enable the draining down of the pipework in severe weather
Insulation is fitted to 750mm below ground level
A double check valve is fitted for backflow prevention
Barry Spick

23. Location of pipework
When planning pipework run try to avoid areas that are difficult to keep warm
Any outside locations, outside walls
Roof spaces, cellars, under floor spaces, garages and any out buildings
Near windows, air bricks and ventilators
If unable to:
Take the appropriate action to protect the pipe.
Barry Spick

24. Why do you fit insulation to pipes?
Water regulations require That cold water systems do not exceed 200C
Insulation to be provided in hot places where cold water pipework passes through
To retain ‘heat energy’
Prevent Condensation
Prevent them freezing
How thick should it be?
Depends upon the size of pipe
Type of insulating material used (Thermal Conductivity)
15mm pipe using polyurethane foam insulation
Min of 31mm thickness
BS 6700:2006, 5.7.3
Barry Spick

25. Insulation Cont’d
Insulating material must be resistant to or protected from:
Mechanical damage
Rain
Moisture
Subsoil water
Vermin
Barry Spick

26. Trace heating Is used on industrial installations What is it?
It is a low temperature heating element
Attached to the outside of the pipe
Controlled by a thermostat
Barry Spick

27. Lesson Complete
Barry Spick