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A recap on domestic water heater installations

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Accidents and deaths caused by incorrect geyser installations are quite unnecessary, and avoidable. All it needs is installers to follow the law. 

Interact Media Defined hosted a wet services forum at its offices in Bedfordview. Chris Kyle compiled and presented an interesting overview of domestic fixed electric water heater installations. 
To recap, this is what the law says:
“All hot water cylinders (geysers) shall be installed in strict accordance with SANS 10254:2004 and must include all pressure control valves, vacuum breakers, drip trays and discharge pipes from valves as prescribed.”
This unfortunately does not happen every time a new geyser is installed, and that is the problem.

A little bit of history: The combination type geyser
Early electric water heaters were simply open vented containers with a thermostat and element fitted to the inside to heat the water and control the temperature much like a kettle. A cistern type header tank controlled the level of the water in the system.
The disadvantages of these geysers are:
• Poor hot water pressure
• Severely unbalanced hot and cold water supply
• Prone to contamination
• Energy inefficient
• Provides poor end user comfort.

Ratio valve
Later development saw the use of an open ended vent pipe being used in conjunction with a ‘ratio’ valve which could be set to adjust the head of water to the hot water system. The additional head improved hot water pressure to the taps and fittings slightly.
A disadvantages with the ratio valve is much the same as the combination tank fed open vented systems while the advantages is a slightly improved hot water pressure to taps and fittings with marginally improved user comfort.

The pressurised closed hot water cylinder
The first closed pressurized hot water cylinders were introduced in the late 60’s and early 70’s and were at first available as 100kPa working pressure systems only. However, this led to the concept of balanced hot and cold water systems, which dramatically improved user comfort and safety. And, as technology advanced, and the use of more suitable materials was explored, so system working pressures increased, first to 200kPa, then to 400kPa and higher to as much as 600kPa as we find today.

Compulsory national standards for plumbing
The Government Gazette 22355 dated 08/02/2001, notice R509 in terms of Water Services Act (Act No. 108 of 1997) Section 9 (1) and 73 (1) (j) “Regulations : Compulsory National Standards and Measures to Conserve Water, refers.

A few general considerations:
An isolating valve will be provided where a pipe enters any building or any portion of a building in separate occupation.
An isolating valve shall be installed on the upstream side of the pressure control valve. Such valve will be a separate valve and not an integral part of the pressure control valve.
All components will be of an approved type (SABS). 

A water meter must be provided on the feed to: A) individual dwellings in a sectional title development, group housing or apartment building. B) Individual building with a max design flow >60 l/min in a commercial or industrial complex. 
The rated pressure of the system will not exceed 600 Kpa (SANS 10252:1) and all the valves used in the system will have the same pressure rating, which pressure can be less than the rated pressure of the storage water heater but will never exceed it.
All pipe work connected to, and all protective valves associated with water heaters will be connected by flush unions or connectors, to facilitate the easy replacement of such fittings. No water heater or storage tank of capacity in excess of 200 ltrs will be attached by means of brackets or hangers to a load bearing masonry wall or concrete wall or to any vertical structural element.
The system will be designed such that it is statically balanced and dynamically balanced within 20 percent hot and cold. Where appropriate, an acceptable balancing device must be introduced in the reticulation pipe work to dynamically balance the system.

References:
SANS 10254:2004   Installation, repair and maintenance of fixed electric water heaters.
SANS 10252:1         Water supply installations for buildings.  
SANS 151                Fixed electric water heaters.
SANS 198                Functional control valves.
SANS 1848              Geyser drip trays.
SANS 10142-1         Electrical wiring of premises.
These are amongst many other considerations.

1. Feed to geyser – 20 mm
2. Cobra ball cock - SANS 1056
3. Cobra pressure control valve - Combined pressure reducing and expansion relief valve - SANS 198.
4. Cobra vacuum breaker - Installed on anti siphon loops on hot and cold inlets and outlets – 30 cm above geyser – SANS 198.
5. Cobra pressure and temperature safety valve - This valve will avert a geyser explosion and so it is very important that it is installed correctly - SANS 198.
6 Temperatures and pressure safety valve discharge pipe - Piped to suitable point of discharge where the drip will be visible, not create a nuisance or hazard and the pipe cannot become blocked. This pipe will be of 20 mm metal (22 mm copper is a good choice)
Note: If the system is installed and working properly there should be no discharge from this piparecapondomestic5e. A discharge from this pipe is indicative of a system fault. The pipe must be kept as short as possible with a constant fall to the outlet with no water traps may not discharge into the drip tray.
7. Expansion relief discharge pipe – Piped to a suitable point of discharge such as a gully where the drip will be visible and not create a nuisance or hazard and cannot become blocked. 15 mm copper is a good choice.
Note: This pipe will yield a drip due to expansion of water in the geyser as it is heated, this is normal. A constant flow of water from this pipe is indicative of a system fault)
Note: Pipes 6 and 7 must never be interconnected but must be kept separate. Both pipes must be as straight and short as possible with a fall away from the valves and to the outlets. Each will be installed such that there are no water traps created within.
8. Cobra drain cock -  Used to drain the geyser for maintenance purposes- SANS 198.
9. Drip tray – SANS 1848
10 Drip tray discharge pipe – 50 mm P.V.C. to a suitable point of discharge.
11 Geyser support – Geyser support and fixing brackets (feet) with suitable timber support under for horizontal geysers. See SANS 10254:2004
12. Balanced hot and cold supply to installation – 22 mm.
 13. Hot water cylinder – Size as appropriate for installation - SANS 151.

Safetyarecapondomestic4
The designer, installer and the owner or operator of an installation is responsible for the safety of the user. If incorrectly designed, installed and maintained, plumbing systems can be hazardous.
Explosions caused by sudden expansion. Hot water cylinders must be installed:
a) In strict compliance with SANS 10254:2004
b) With all required safety devices and control valves, drip trays etc.
c) Quality of vital components for example, SANS 198 for valves- SANS 151 for Geysers. 
Super heated water is a condition which will exist when water is heated to its boiling point under pressure i.e. more than one atmosphere.

Super heated water
In a condition where super heated water contained in a pressure vessel is released to the ambient atmosphere it changes immediately from a liquid to gas (steam). In this process a huge amount of energy is released in the form of very rapid and violent expansion. This change of state from liquid to gas is enough to cause an explosion equal to 1 kg of dynamite in a 150 litre geyser ( 150 litres of water becomes almost 255 000 litres of steam in an instant).
Such explosions have occurred frequently in the past and are caused due to poor design, installation, maintenance, non compliant product and negligence. People have been killed and structures destroyed.

arecapondomestic62) Scalding or burning
First degree burns can be obtained in 1 to 1.5 seconds at water temperature of 55ºC. Hot water is stored at 65ºC.
A few points that need to be considered. Where flush masters are used a two pipe system must be installed. Thermostatic mixers should be fitted in critical areas. A common mistake made is to feed flush masters off the balanced cold water line. Firstly the flow rates required for flush masters to operate properly exceed the flow capability of geyser pressure control valves. Secondly flush masters usually require larger pipes to feed them. Thirdly the transient high load on the cold balanced line is high enough to cause cold water starvation to the showers, leading to poor user comfort and possible scalding.

3) Bacteria
This is reference to SANS 10252:1. Rubber components will not form a source of nutrient for bacterium. Storage tanks will be contamination proof and have facilities for cleaning and scouring. The temperature of cold water in storage should not to exceed 20 degrees Celsius. Hot water storage zones will not be kept in a luke-warm state at 25 to 45 degrees Celsius. The presence of organic matter in the water as well as final products of metal corrosion will be kept to a minimum.
The bacterium Legionaella Pneumophila infection by inhalation of fine droplets kills.

What is Legionella?
Legionellosis is a group of respiratory diseases caused by ‘legionellae’. The Legionella genus includes a wide variety of species
(43 known).
• Legionella organisms are opportunistic pathogens and are the causative agents of Legionellosis, a disease causing an acute fulminating pneumonia which can be fatal.
• Legionellae are ubiquitous in the natural environment and live in soil and water in association with other bacteria and protozoa, especially in biofilms.
Biofilms can form in water supply systems which can become colonised with legionellae.

Selection of piping material
All materials used will comply with the requirements of sans10252:1, however research has shown copper surfaces were shown to inhibit pathogens such as Legionaella Pneumophila. Other materials did not inhibit the growth of these organisms’. (SCHOENEN & SCHLOMER, 1989). Legionaella Pneumophila could survive and grow in the biofilms, even at temperatures up to 50ºc on plastic surfaces but not copper’ (Rogers et al 1994a,b).
Plastic and rubber materials can actively encourage the growth of micro-organisms (ZOBELL & BECKWITH, 1944; BURMAN et al., 19977). Legionaella Pneumophila is sensitive to copper and can only colonise biofilms on aged copper surfaces (article by Dr. HAROLD T. MICHELS November 2004).

It must be noted that Legionella is relatively resistant to chlorination and that it is the presence of a biofilm that it thrives on.
After some years, once scaling takes place in the piping and a biofilm is able to form there may not be much difference in the type of material used. Monitoring and maintenance of the system becomes all important.
Polyvinyl chlorite (PVC) and high-density polyethylene (HDPE) are commonly used in sub surface water supply service piping where ambient water temperatures are relatively low. Copper is a good selection for pipe work within the building because of its ‘intrinsic’ qualities to inhibit the growth of micro-organisms, especially in the beginning of the life of a building and in parts of the building not often used or on ‘dead legs.’
It is very important however to select materials only compliant with the South African national standards, since they have been tested and approved for the conveyance of potable water fit for human consumption and use.

A system yielding a high level of risk is any system or apparatus that produces a fine or atomised spray of water. For example:
• Domestic hot and cold water systems – especially showers
• Water storage tanks
• Hydrotherapy pools, hand sprays and emergency showers
• Water features and fountains
• Drinking fountains and localised water filters

And any water dispensing point that is at the end of long dead leg
• Fire protection systems
• Air conditioning systems and cooling towers
• Patient and other humidifiers
• Fine spray from high pressure wash down hoses

To minimize bacterial growth in plumbing systems- here are a few tips:
• Ensure that all fittings and materials are compliant with SANS e.g. taps SANS 226
• Systems are installed in compliance with SANS and can be flushed periodically
• Water not present for any length of time or stored within the system at temperatures 25 to 45 degrees Celcius
• Thermostatic blending of water is as close to terminal fittings as possible

Dead legs, SANS 10252:1 ; 7.7.1.3, states; unless stated otherwise, the length of an unheated pipe (dead leg) conveying hot water directly from a fixed water heater to a terminal water fitting, or from a point of take-off from a hot water circulating system (ring) to a terminal water fitting, will be such that the internal volume of that pipe does not exceed four litres.
Exposed hot water pipes must always be lagged to save water and energy.

4) Backflow of contaminated water arecapondomestic5
This is caused by combined domestic and fire installations, type of buildings, unapproved terminal fittings and illegal water
connections. A correct design input is required to ensure the prevention of backflow of contaminated water.
To minimize the risk of backflow of contaminated water one must ensure that all terminal fittings and installations are compliant with SANS 10252:1 and geyser installations must be compliant with SANS 10254 and must be fitted with an anti-siphon loops and vacuum breakers.
Refer to SANS 10252:1 in instances where backflow prevention is required.

The components of the system: the purpose, function and method of operation
The pressure control valve (SANS 198)

The Valve performs two functions, to reduce the incoming main supply pressure to the geyser installation to a value which is compatible to the pressure rating of the geyser and the system. Secondly, to relieve excess pressure in the geyser and system caused by the thermal expansion of the water being heated in the geyser.
The Valve is closes when all taps and fittings are closed downstream. 
arecapondomestic3

In the closed position the regulating seat washer 1 seals against the regulating seat 2 thus separating the high inlet pressure area P1 from the low pressure outlet area P2. In this position the downward force of the compression spring 3 is counter balanced by the next upward force of the regulating spring 4 and the downstream water pressure in area P2 acting against the underside of the diaphragm 5. The forces acting on the surface areas of the regulating spindle 6 are in equilibrium since the inlet pressure in area P1 acts on equal and opposite surface areas, therefore the pressure in area P1 has no effect on the pressure setting of the valve and so the valve remains pressure balanced in this state. 
The Valve Opens when a tap/s or water fitting/s is opened. arecapondomestic2
Opening a water fitting downstream of outlet pressure area P2 will result in a drop of water pressure under the diaphragm 5 allowing the compression spring 3 to force the regulating spindle assembly 6 down ward. The regulating seat washer 1 thus no longer seals against the regulating seat 2 and water can now flow from the high pressure area P1 to low pressure area P2. When closing the water fitting the increased back pressure under diaphragm 5 will counteract the tension of the extended compression spring 3 thus closing the valve at the preset operating pressure.

The expansion control valve opens when the system pressure rises due to thermal expansion as water is heated in the geyser

When the down stream system pressure in area P2 rises above a preset value due to thermal expansion or a system fault, the aarecapondomestic1dditional force under diaphragm 5 further compresses spring 3 thus lifting the relief seat 6 away from the relief seat washer 7 allowing water to escape through the relief port 8 thereby maintaining the preset working pressure of the system.

The expansion relief valve should only discharge while water is being heated from T1 to T2 in the geyser. If it continuously discharges after the heating cycle is complete then there is a fault in the system.
The most likely cause is unbalanced cold water back pressure caused by a wrong installation or there is dirt under the Relief Valve seat or the Valve has failed mechanically.

Approximate expected expansion relief valve discharge for one heating cycle from 15°C - 65°C as follows. Remember the expansion relief valve is a functional valve and discharge from it is normal.
Formula for Thermal expansion: V2 = T2 – T1 x V1 x 0.0004
Where:  V2:  volume of expansion (litres)
              T2:  raised temp of water ° C  
              T1:  ambient water temp ° C
              V1:   volume of water (litres)

It’s important to note that no Shut-off Valve, Isolating Valve or Non Return Valve may be installed between a pressure control valve or expansion relief valve and the Geyser.
Two geysers can be fed by one PCV provided that the geysers are not in separate occupation and the max flow rate required does not exceed that of the capabilities of the PCV. Also it must be realised that should one geyser need maintenance then the water supply to both geysers will be closed due to the above rule. For very little extra cost it is always better to have a dedicated PCV for each geyser.

Important note:

In the hot and cold balanced water reticulation system always try to feed the shower or showers first on line and then other fittings such as baths, basins and sinks.   

In cases where geysers are fed from header tanks, separate expansion relief valves can be used in replacement of pressure control valves, provided that the head of the tank does not exceed the working pressure of the system and that there is no intention of feeding the system from time to time from another source of direct supply, the pressure of which being greater than the working pressure of the system.

The temperature and pressure safety valve - SANS 198
The valve performs two functions, to protect the system from excess temperature and to protect against super heated water conditions where a system fault occurs. The Second function is to provide a back-up line of defense to the expansion relief valve. It will open under pressure should the expansion relief valve fail closed or become blocked.
It is the most important valve in the system and alone will prevent an explosion if installed correctly. 22 mm safety valve discharge pipe to suitable point where drip will be visible, cannot become blocked, not create a nuisance, hazard or damage. It must be metallic and as short and straight as possible with constant fall away from the valve with no water traps created and may not be piped into a drip tray.

The temperature and pressure safety valve is a non functional valve and should not open unless there is a system fault where the temperature in the geyser reaches 93°C and greater or the pressure in the geyser  reaches 1.5 times the working pressure of the geyser.
The valve will open when the pressure in the geyser reaches 1.5 times the system working pressure and will only open ‘OVER PRESSURE’ if the expansion relief valve is either blocked or there is a system fault or incorrect installation.
E.G. in a 400 kPa system (Red Label) the safety valve will open if the pressure in the system reaches roughly 600 kPa. (1.5 x 400 kPa = 600 kPa).
In normally operating systems the safety valve should not open, If it does open, the temperature is too high in the geyser. This could mean that the thermostat set too high or faulty – temperature reaching 93 - 95°C or a there’s Faulty electrical connection – direct wiring by-
passing thermostat.

It is easy to check, the electrical supply must be switched off, there after the hot water tap should be opened to allow it to run for some time in order to cool the system down. If the safety valve closes and does not leak anymore with the electrical supply off then it is an over temperature condition.
If the pressure is too high, this causes blockages or there’s no expansion relief valve. It is important that Non Return Valve or Stop-cock are fitted between Geyser and expansion relief valve. No expansion relief valve must be fitted in system and unmatched pressure ratings of valves.
Warning!!! Because the safety valve can expel water at very high temperatures, care must be taken as to where such discharge pipes are led. Such high water temperatures can badly injure people and animals as well as cause damage to other materials into which it discharges.

Under no circumstances may the expansion relief discharge pipe be interconnected with the safety valve discharge pipe. The reason for this is that should the single discharge pipe become blocked then the expansion relief valve and safety valve will both become redundant.
Neither of these discharge pipes may be plumbed such as to discharge into the drip tray.

The Vacuum breaker (SANS 198)

The valve performs only one function and that is to allow air into the system to prevent back siphoning of water.
The vacuum breaker is also a non functional valve and remains closed all of the time as long as the system is pressurised. Water pressure in the system securely forces the jumper closed against the sealing seat and thus the valve is closed. Well designed vacuum breakers have double jumpers as a failsafe feature. There is a spring of very low tension that locates the jumper against the seat.  Some models are nothing more than a low resistance non return valve.
At any time there is a negative pressure in the system such ‘suction’ will draw the Jumpers off of their sealing seats and air will be inducted into the system thus breaking any siphoning action. In this way ‘back siphoning’ of water from the system is precluded. SANS 198 Spec requires that vacuum breakers should open under a negative pressure of – 3 kPa, hence the height requirement of 30 cm above the ‘anti siphon loop’.     

Vacuum breakers installed on siphon loops allow air into the system under vacuum therefore making the Siphon Loops ANTI – SIPHON LOOPS.
Note: Vacuum breakers do not have a colour code or pressure rating. Common fault: although vacuum breaker is 30 cm above supply pipe and geyser, it is not on an anti- Siphon loop.
• General information about geysers
• Inner cylinder is usually manufactured from 1.6 mm high grade engineering steel.
• Most manufacturers line the inside of the pressure vessel with vitreous enamel. There are some that use a PEX polymer to line the cylinder.
• All SANS 151 Cylinders are fitted with a magnesium sacrificial anode which must be checked and replaced periodically.
• Incoloy alloy elements can be specified where installed in harsh water conditions.
• Outer casings are usually galvanised mild steel or chromadek for outside installations or where aesthetics is a consideration.
• Insulation is usually high density polyurethane.
• Vertical geyser are more efficient (energy) than horizontal ones.
• Most manufacturers produce dual purpose geysers that can either be installed vertically or horizontally.

Some more installation tips
• Allow sufficient space around the geyser for maintenance and removal and replacement of components such as anodes, thermostats and elements.
• Install the geyser as close as possible to fittings to minimise the length of ‘dead legs’ especially points where small draw offs will be required frequently such as kitchen sinks.
• Place preferably over a load bearing wall.
• Drip trays must be installed - refer to SANS 10254 Annex B. ‘The installation of Drip trays’ B. 1 General, B 2.1 & B 2.2. Also SANS 10252:1 – 8.2.4 Safety trays.  

NEW SANS CODES
SANS 10400 PART XA .
 50 percent of hot water generated will be by renewable energy sources. New specification of lagging of hot water piping.
SANS 204 energy efficient buildings
SANS 10106 The installation, maintenance, repair and replacement of domestic solar water heating systems
SANS 1307 Annex D Domestic solar water heaters

Plumbing considerations when - designing new facilities:
• Attempt to group sanitary fittings in close proximity to one another
•  If more than one level, try to make layout typical - utilising alligned vertical ducts. Or if a typical layout is not possible then at least try to keep wet services vertically grouped
•  Allow sufficient space for these ducts with maintenance considerations in mind
•  If individual geysers are used at wet areas allow sufficient and suitable space for their installation bearing points of discharge from safety devices in mind. SANS 10254
•  avoid the need for long ‘dead legs’ of hot water piping by keeping fittings requiring hot water as close to one another as possible
•  ensure that geysers are installed in compliance with SANS 10254

Pointers to designers, installers and operators
Designers:
Ensure that your design is based on recommended practice and in line with SANS.

Installers:
Ensure that you follow the designer’s drawings, recommendations and specifications using only approved materials.

Operators:
Enforce your standard operating procedure (SOP’s), management and maintenance of a well designed and installed plumbing system is paramount. Even the best system in the world will eventually fail if not managed and maintained in a responsible manner. Remember the onus lies on your shoulders.

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