PLUMBING

Above ground drainage (Soil and vent)

Above ground pipework systems should be designed and installed to meet the following performance requirements:

• Liquid and solid wastes from soil and waste appliances should be carried away quickly and quietly without blockage and without the entry of foul air into the building.
• Sanitary discharge pipework relies on gravity flow and should be kept as short as possible, with few bends and adequate pipe gradients for best performance.
• Prevention of foul air into the building is achieved by providing each sanitary fixture with a water-seal trap, either as part of the fixture as found in toilets or as a separate fitting to the outlet of the fixture. The retention of an effective water barrier by protecting trap seals is essential if this design aim is to be achieved.

A trap seal will be broken if changes of pressure in a branch pipe are great enough to overcome the head of water in the trap by self siphonage or induced siphonage and back pressure due to suction (negative air pressure) in the discharge stack.

To prevent failure of the trap seal in order to maintain adequate water seals in the traps of sanitary fixtures, it is necessary to limit changes in the air pressure within the pipe system. The traditional way of doing this is to provide an extensive system of vent piping with the object of equalizing air pressures throughout the system. In the fully vented two-pipe systems, vent pipes are used to ensure that the pressure in the branch pipes never differs greatly from that in the open air.

Waste

The following general information is provided on waste pipes and what diameter and pipe lengths are best suited to specific applications.

Waste discharge pipes (nominal sizes)

• 32mm Ø Inside dimension = 40mm Ø Outside dimension
• 40mm Ø Inside dimension = 50mm Ø Outside dimension

Wash hand basins; discharge pipes of 32 mm Ø. Lengths and slopes need to be finely controlled if venting is to be avoided.

Banks of wash hand basins; venting is often needed, though not for ranges of up to four WHB’s and pipe lengths up to 4.0 m.

Bidets; the same arrangements apply as for wash hand basins with plug wastes.

Below ground drainage ‘underground’

Pipes concealed in the construction of buildings, beneath houses and underground represent to many a vague and mysterious technical area, unglamorous to the extent of being considered unmentionable. Hardly an interesting topic yet, when the system fails, a subject hard to ignore. Those hidden and hardworking pipes, whether appreciated or taken for granted are nevertheless with us as a continuing part of life where certain standards of hygiene, responsibility to the environment, convenience and comfort are expected.

Drain basics

• The nominal diameter of any drain is in no case to be less than 100mm Ø (ID) and the diameter of drains may not be reversed in the direction of flow.
• Where due to the slope of the ground any drain is required to be laid at a gradient steeper than 1 in 5, the hydraulic load carried by the drain shall not exceed the maximum permissible drain loads as described in SANS 10400 Part P.
• Drains of 100mm Ø may not be laid at gradients less than 1 in 150. Special permission from the local authority is required for laying 100mm Ø drains at gradients of 1 in 80, 1 in 100 and, 1 in 120.
• A ventilation pipe shall be placed at a point not more than 6 metres from the head of the main drain and at the head of every branch drain whose developed length, from outlet of the trap of the sanitary fixture to the point of connection to a ventilated drain exceeds 6 metres.
• Where drains pass under buildings, access to the installation must be provided outside of and as close as possible to the building at the pipe entry and exit points and must be laid without change in direction or gradient.
• Permanent access must be provided for cleaning purposes to the interior of any discharge pipe, where it enters the ground and within 2 meters above ground level.

Other pipe sizes and gradients are dealt with in the various documents which exemplify the national building regulations: SANS 10400.

Drainage materials

Pipe materials used in the construction of domestic drains and small diameter sewers includes uPVC, cast iron, ductile iron, vitrified clay and concrete. uPVC is the most commonly used material in typical domestic drainage applications “above and below ground”. Cast Iron or ductile Iron is typically used in multi storey buildings and applications where plastics are not suitable. Vitrified clay “Earthenware” is seldom used in domestic applications and concrete typically used for sewer mains and stormwater applications.

Knowledge and attention to detail regarding cutting, jointing, and connection to other materials, trench preparation (bedding) and backfill considerations and loadings are vital to the correct use of whatever pipe material is specified or selected. Drain pipes fall into two categories: flexible pipes; which are made from materials such as plastics, and rigid pipes; which are made from concrete, vitrified clay, ductile Iron or cast Iron. The behavior of the two types of pipe in the ground is significantly different; while rigid pipes have an inherent strength, flexible pipes can deform under the application of loading and require support from the surrounding backfill material to prevent excessive deformation. Linear expansion also needs consideration when using flexible pipes.

uPVC

Unplasticised polyvinyl chloride also referred to as PVC-U to some or uPVC is a relatively stiff “rigid” type of polyvinyl chloride, sometimes brittle in cold weather, impervious to water, oil and many chemicals. uPVC has the advantage of being available in long lengths, lightweight, and easily handled and assembled; making this the most commonly used material in domestic drainage applications.

• Underground pipes and fittings (110 and160mm Ø) are normally beige in colour.
• Above ground “soil and vent” pipes and fittings (110 and 75mm Ø) are normally white.
• Waste pipes and fittings (40 and 50mm Ø) are normally white.
• 110mm soil and drain pipes are typically joined using push-fit fittings and 40 and 50mm waste pipes using solvent welded fittings.
• Structured wall or commonly called ‘Twin-wall’ (heavy duty) piping is used in below ground applications where greater wall strength is necessary to prevent distortion of the pipe depending on loading and other site conditions; Twin-wall piping is also available socketed in 6.00 meter lengths only.

uPVC (PVC-U) Pipes and fittings are regulated by the following standards:

• SANS 791: Unplasticised poly(vinyl chloride) (PVC-U) sewer and drain pipes and pipe fittings
• SANS 1601: Structured wall pipes and fittings of uPVC for buried drainage and sewerage.
• SANS 967: Unplasticised poly(vinyl chloride) (PVC-U) waste and vent pipes and fittings

Cast Iron and Ductile Iron

Iron pipes were traditionally made from crude cast iron (grey iron), however, ductile iron pipes, made from a modified form of cast iron, are now also available. Ductile iron pipes have a much higher resistance to impact than cast iron, and can be struck and dented without fracturing. This makes them particularly useful in situations where there is risk of severe impact loadings; e.g. shallow cover depth below a road.

Although iron pipes are not extensively used for drainage underground, their high strength makes them suitable for applications where special protection would otherwise be needed.

Most drains constructed up until the 1960s, will be Vitrified or fired clay. The pipes produced were of 4” and 6 “diameters and lengths were limited to 2 or 3 ft by the risk of distortion during firing. Jointing was by caulking with hemp yarn and forcing Portland cement based mortar into the socket. If the hemp was not fully inserted, there was a risk of mortar protruding into the pipe, which explains the old procedure of dragging a ball of sacking through the pipe immediately after laying and before testing. The joints between the pipes were obviously rigid and therefore extremely susceptible to damage from ground movement.

During the 1960s and 1970s practice changed considerably, with the introduction of fired clay pipes which were no longer glazed. These pipes have proved to be no less suitable for a given usage than the older glazed variety. There is no significant difference in hydraulic resistance in service; the modern pipe with its greater length and more accurate jointing may often prove superior.

• The performance of modern clay pipes has been vastly improved by the introduction of flexible ‘O’ ring seals and plastics couplings.
• Vitrified clay pipes remain popular because of their resistance to attack by a wide range of substances, both acid and alkaline.

Vitrified clay pipes and fittings are regulated by the following standards;

• SANS 559: Vitrified clay sewer pipes and fittings.

Pipes and fittings are available with nominal bores of 100mm upwards; in lengths of 0.3 – 2.5 m and, depending on size, in different strength classes.

Gulleys

Gulleys are not only part of sewer “drains”, they can also be used as outlets for stormwater or as surface outlets for the disposal of water used for washing down floors in bathrooms or kitchens. Surface gulleys remove water or stormwater from the vicinity of buildings, and other hard surfaces, to appropriate disposal points. The major difference from sewer drainage is in the provision of access, including intercepting traps and trapped gulleys. The latter two are needed only where the system eventually connects to sewer drain. Gulleys, whether trapped or not, should be provided with grates to prevent the possibility of foreign substances entering the drain.

Wastes

A waste union can be described as a threaded outlet pipe fitted to the plug hole of a basin, sink, wash trough or bath. It has a flange that goes on the inside and typically a smooth collar which is inserted through the sanitary fixture (in the case of a basin waste it can be slotted to allow for the fitted overflow to discharge into the waste). On the outside of the fixture it has a threaded tail pipe to which a sealing washer and back-nut are tightened to secure the waste union to the sanitary fixture; to which a trap is usually then fitted over the treaded tail (see traps).

Drainage tests

It is obvious that building regulations play a very important role when it comes to plumbing and they fulfil a very important purpose associated with this trade and thus cannot be ignored. It is also important to note that all local authorities apply these national building regulations coupled with their own by-laws. It is therefore imperative that the local council be consulted before any plumbing work and more especially drainage is undertaken.

Hot Water Systems

Types

Electric

In years gone by low-pressure roof tank fed, vented hot water systems were common; then in the 1970’s manufacturers were working hard at developing mains fed closed pressurized systems in which steel tank hot water cylinders could be capable of handling higher pressures. The Industry settled on 100Kpa and 200Kpa for copper tank geysers and 400kPa for steel tank geysers.

During this time domestic pressure geysers started exploding, the cause was soon identified as electrical control failure, causing the water to superheat with the potential to explode. At the time it was mistakenly thought the controls and protection built into the thermostat and electrical circuitry would be adequate. The solution was found by adopting the safety practice used in America and Europe, resulting in the first mechanical temperature and pressure safety valves, which would open and relieve water from the geyser before it reached boiling point and so prevent an explosion.

The Pressure Control Valve or Pressure Reducing Valve only has one function and that is to reduce the mains pressure to a constant working pressure. If the pressure rises downstream due to any reason it cannot rectify the system pressure. Pressure control valves are of the pressure balanced type, which means that the set pressure (outlet) is unaffected by changes in the supply pressure (inlet) i.e. the set pressure to the geyser will remain constant.

The PCV is normally installed in an incoming water mains line, before it enters the building. The PCV ensures that the system is not over-pressurised by high pressure spikes or surges, which would cause water wastage through full discharge from the geyser safety valves if no pressure control valves were fitted and any other potential damage to the various fittings in the distribution system which could have a lesser pressure rating.

Many PCV’s have the added advantage of acting as a strainer to the water distribution system of dwellings; when they are fitted with a strainer/filter which eliminates sediment, dirt and unwanted particles into the water system. (This is a removable part that can be cleaned and serviced).

Expansion relief is combined in the pressure control valve; during the heating cycle water will expand and increase in its volume. As water is not compressible an increase in pressure takes place. This increased pressure is released through the expansion relief valve.

The function of this valve is to protect the hot water cylinder from over-pressurizing when the water in the cylinder is heated. When the pressure inside the hot water cylinder rises, due to the heating process, the pressure valve would open should the pressure inside the cylinder exceed the set pressure of the pressure safety valve. The safety valve is designed to release water if the pressure in the system exceeds 1.5 times the rated working pressure, i.e. 900 kPa for a 600kPa geyser – See Table 16.9 above.

It is also set to release if the temperature exceeds 98°C. An over temperature condition is normally as a result of thermostat failure.

• The safety valve will discharge over heated water until it senses that the water has sufficiently cooled and then close. This process will continue until the over temperature condition is rectified.
• In an over pressure condition the safety valve will discharge continuously until the source of over pressure is eliminated.

Solar hot water systems use sunlight to heat water. South Africa has the ideal climate for solar energy and experiences some of the highest levels of solar radiation in the world.

On average about 40% to 45% of electricity used in South African homes is for water heating, using the traditional ‘electric geyser’. However, the National Building Regulation for energy usage in buildings SANS 10400 Part XA as described earlier require that 50% by volume of the annual average hot water heating requirement shall be provided by means other than electric resistance heating or fossil fuels, of which solar is one of the alternatives.

The most common types of solar water heaters used are evacuated tube collectors and glazed flat plate collectors generally used for domestic hot water systems; and unglazed plastic collectors used mainly to heat swimming pools.

Solar water heaters make use of two natural phenomena for their operation: Black objects absorb heat and hot water rises.

Correct collector orientation and inclination is imperative when installing a solar water system. These two angles will affect the overall performance and efficiency of the solar hot water system.

Whenever possible collectors should face true north in the Southern hemisphere; If the collector cannot be installed facing north, an orientation facing slightly west is more advantageous than east, due to higher ambient temperatures in the afternoon. A deviation of 45° east or west will have no major effect on the collector efficiency. However deviations greater than this will require extra square meters of collectors to compensate for solar losses.

The rule of thumb for pitching the collectors is latitude +10°. This will give more of a uniform solar collection from month to month. In summer, energy collection is reduced due to high solar reflection, and in winter when the sun is lower on the horizon, the maximum energy is captured. However with an efficient collector, variation of performance is relatively insensitive to collector orientation within ±50° of the northsouth line for low latitudes, but becomes more significant at high latitudes. For installations near the equator, performance is obtained for inclinations within 15° of the latitude angle.

Cape Town has latitude of 33° south and Johannesburg has latitude of 26° south. If your roof angle is within 10° of your desired angle you can mount the solar collector flush against the roof surface. If the roof pitch is not ideal, it is generally cheaper and neater to install an extra collector than use a frame to achieve the optimum performance.

Open circuit systems simply circulate the (potable) water directly from the HWC through the collectors and then directly to the buildings hot water supply. This system is ideal for locations where the ambient temperature never falls below freezing and where the water quality is good. As most areas in South Africa regularly have temperatures below freezing in winter as well as regular incidence of frost, and due to the calcium content in many areas, the open/direct system is generally not considered viable. A direct system should only be used where the following conditions prevail;

• Frost free areas
• Lime free water
• A not too aggressive water/soft water to prevent long term corrosion

These systems are generally less expensive than indirect systems, as no heat exchanger is required and where the use of a heat transfer fluid is eliminated.

Solar water heating systems are available in both pressurised and low-pressurised systems:

Pressurised System

This system uses the water pressure of the mains.

Low-pressure System

This system is an open-loop; gravity fed system and relies on the thermosyphon phenomenon (also commonly termed as a Thermosyphon Solar Heated Water System). Warm water rises to circulate the water through the tubes to the tank. Mains water flows into the tank via a feeder tank similar to that of a toiler cistern and then to the lower part of the vacuum tubes, where it is heated. The water ascends in the tubes as it’s heated, and flows on to the tank before going to the user.

Thermosyphon systems or as some call passive systems are complete on-roof hot water systems, in which the storage tanks and solar collectors are mounted on the roof as a unit either as an integral or close coupled combination.

In a direct system the cold and hot water supply lines are connected to the domestic (potable) water system. Due to the solar irradiation and differences in the specific weight of cold and hot water, the heated water rises to the top of the collector where it flows into the storage tank and displaces the cold water in the storage tank, which in turn flows into the collector and is heated there.

The heated water then flows into the hot water lines and can be used directly for cooking, washing or showering. The advantage is that this circulation method is often the most economical solution; the technology is fool proof and requires almost no maintenance. If the sun does not shine for several days or the water consumption rate is abnormally high, the storage tank can have an electric element installed where a thermostat automatically activates the electric element.

In an indirect system the heat transfer fluid is heated in the collector, and where the ‘thermosyphon circulation phenomenon’ causes it to flow to the tank where a passive heat exchanger transfers the heat of the HTF to the (potable) water in the tank.

Pump-Circulated

In a “pump-circulated” system or active system the storage tank or HWC is usually installed in the roof or separately from the collectors and usually below the level of the collectors; a circulating pump moves water or heat transfer fluid between the tank and the collectors hence the terminology active. This pump can be electrically or solar operated.

If solar operated a photovoltaic (PV) panel is used to drive the pump in an active system, and the installation of a controller is crucial. This prevents the pump from switching on early in the morning when there is light to drive the pump but while the collector is still cold, which causes the hot water in the storage tank to be cooled.

Flat plate

The principle of operation is relatively simple, although there have been advances in the construction technology, materials and absorber surface that are used by different manufacturers.

All flat plate collectors have a collector box, usually fabricated from aluminium. The absorber plate, with tubes attached for heat transfer to take place, is placed within the box. Beneath the absorber plate is insulation, to prevent the loss of heat through the bottom of the box. Above the plate is a transparent cover, usually glass, which is designed to absorb solar radiation and convert it to heat in the absorber plate.

Evacuated tubes are more complex than flat plate collectors – originally developed for northern hemisphere climates, where solar radiation is relatively low. Evacuated tube collectors all have evacuated glass tubes which are connected to a header pipe that is housed in a manifold box and secured to a frame.

Evacuated tube collectors use two glass tubes, in between which a vacuum has been created. The outer glass tube and the vacuum within protect the absorbent coating and structural materials from corrosion. The absorbent coating is most often a thin layer of barium.

The evacuated tube system is rather like a thermos flask, with a vacuum in the space between the walls. The vacuum is a very effective insulator, eliminating conduction and convection. The heat arrives through the vacuum, as radiation, and is absorbed by the coating on the inner tube.

The heat from the absorbent coating is transferred to the heat conveyance system. The fluid heat conveyance is an evaporating-condensing liquid that evaporates in the collector tubes, and then transfers the latent energy (heat) to the cold water in a manifold, through condensation.

System sizing is not the same when compared to a conventional electric hot water cylinders. Correct sizing of solar water systems is imperative for maximum savings. The size of the system involves the sizing of two components:

• The hot water storage tank, and
• The collector area or number of collectors

The first calculation that needs to be assessed is the number of litres of hot water required for daily use. This will vary enormously from family to family, but a rule of thumb of 50 to 80 litres of hot water per person per day would assist in your assessment.

A rough rule of thumb for collector size (area), is 1m² of collector per person, plus 1m² for each major appliance using hot water, for example a dishwasher.

A heat pump is a ‘machine operating on a reversed heat engine cycle to produce a heating effect’. Energy from a low temperature source (e.g. earth) is absorbed by the working fluid, which is mechanically compressed, resulting in a temperature increase. The high temperature energy is transferred in a ‘heat exchanger’. The operation of a heat pump has been likened to that of a refrigerator, though saving and using the heat instead of throwing it away. Most applications have achieved a coefficient of performance (COP) of around 3; that is to say, the output is something like three times as great as the input.

A technology that is simple and effective in lowering electricity consumption is the heat pump. Heat pumps offer households and commerce and industry an opportunity to reduce water heating costs significantly.

Gas Water Heaters (GWH) have been called many different names in the past; gas geysers, instant water heaters, pushthrough geysers, tankless water heaters etc. These units have been around for decades and are the preferred method of efficiently heating water around the world. Why – because they heat water on demand, only as you turn on the hot tap will the unit start to produce hot water, meaning extremely high efficiency and very little heat loss.

GWH’s are measured by the ‘flow rate’ of hot water they can deliver. The older traditional GWH’s provided between 11-18 l/m, enough for single use (1 tap at a time). Modern GWH units come in 20 & 26 l/m which allow for multi-point use (dependent on climate) with up to 3 taps/showers used at any one time.

Over the years, GWH’s have developed enormously; gone are the days of running outside to relight gas geysers, also gone are the days of lukewarm and weak showers, with cries from the cold water coming through after someone else opens another hot tap while you shower.

Why Use Gas Water Heating

• Unlimited hot water (as long as you have gas)
• No hot water is stored (heating on demand)
• Low maintenance, Low capital outlay
• Can pay for itself in 8-10 months (LPG Installation) or 4-6 months (Natural Gas Installation)
• Can be retrofitted to current hot water OR SOLAR systems
• Cost savings in 3 forms;
  • 1. Pay as you use hot water
  • 2. No storage of hot water,
  • 3. Lower cost of heating water with gas

Stormwater disposal in becoming a very important part of the planning process and looking after our built environment. With many local authorities requiring a stormwater plan showing what provisions and interventions are included to control stormwater especially with new developments.

Note: Stormwater control means the control of the rate and volume of stormwater released from a development site or site, and includes attenuation, detention and retention facilities.

See Siteworks – Erosion and stormwater control and dewatering techniques for more information.

Rainwater disposal

A considerable quantity of rainwater falls on roofs during storms. Required practice is for roofs to fall towards gutters, either at the perimeter (if installed) or to valleys, where the water flows, via the required number of downpipes into drains. However many homes are built without gutters and downpipes; where it is at least recommended that one should consider the effects of rainwater around the perimeter of the foundations and specify other means of directing rainwater away from the building; for instance a paved apron.

Where downpipes are used they should be positioned so that they are not needlessly complicated with the layout of gully and or connections to the drains planned. Where overflow of the system may occur (typically during exceptional rainfall) on flat roofs with parapets and non-eaves gutters, the design should include an overflow or emergency outlet to reduce the risk of over spilling of rainwater into the building.

Where no downpipes are used one has to consider the ground water run-off and the ground’s characteristics and existing state of saturation, which can lead to a rise in the level of the water table. If the surface of the ground cannot tolerate more rain, the run-off will need to be disposed of by means of sumps or stormwater drains in the same way that drainage will need to be provided for run-off from paved areas. Much of the rainfall can be encouraged to percolate into the ground, through carefully designed filter strips and swales.

Calcamite septic tank systems

Septic tank and Soak-away – the “Septic System”
Septic systems are used when sewage treatment plants are not accessible. (i.e where On Site Sanitation is required). They safely treat and dispose of waste-waters produced in the bathroom, kitchen, and laundry. These waste-waters may contain disease-causing germs and pollutants that must be treated to protect human health and the environment. Although septic systems are usually a permanent solution to wastewater treatment and disposal, they sometimes serve as a temporary solution until sewer lines are installed. The Septic System consists of s Septic Tank , a Soak-away Field and a suitable subsoil.

The Calcamite2 chamber SABS Certified Septic Tank
The Calcamite Two chamber Septic Tank is a watertight
Polyethylene unit ranging in size from 1000L to 30 000L. It is buried in the ground just outside the home or ablution facility. The size of the tank is legally determined by the number of bedrooms in the home or daily expected flow. (use S.A.N.S 0252 as a reference).The National Building Regulations calls for a minimum size of 1500 liters for Domestic Use. It comes supplied with a manhole lid and all connection and seals.

How does the Calcamite 2 chamber Septic Tank Work?
All of the waste-waters from the home should flow into the septic tank. Even waters from the shower, bathtub, and washing machine can contain disease-causing germs or environmental pollutants. As wastewater flows into the tank, the heavier solid materials settle to the bottom (forming a sludge layer), the lighter greases and fats float to the top (forming a scum layer), and the liquid (sewage effluent) flows out of the tank. An outlet baffle (inner chamber) prevents solids and greases from flowing out with the liquids. Our unique design draws effluent from the cleanest area of the tank and allows this to be transferred to the soak-away system through hydraulic displacement. The tank’s primary purpose is to retain the solids while releasing sewage effluent to the Soak-away. The solids which remain behind are gradually broken down by a process known as Anaerobic Digestion. Here Anaerobic Bacteria digest (consume) Waste and convert them into simpler forms. For example Protein molecules are reduced into Amino acids. Methane gas is produced as a by-product of the Anaerobic Digestion Process.

The Soak-Away
The tank is connected to the Soak-away via the tank outlet pipe. A typical soak-away consists of one or more trenches excavated into the subsoil. In most conventional septic systems, the trenches are 300mm wide, 500mm deep, and 1000mm apart. In each trench, a 150-300 thick layer of washed gravel or stone is placed around a 50mm diameter perforated distribution pipe. After the trenches are covered with soil, the area must be landscaped to keep surface waters from ponding over the Soak-away. Calcamite recommends the installation of the Biological Mat (Biomat) type Soak-away be installed. This system uses a prefabricated concave shaped chamber that replaces the pipe and stones as described above. The Biomat type Soak–away allows for more storage capacity. The Soak-away has also been called the nitrification field or the soil absorption field.

The sole purpose of the Soak-away is to deliver wastewater to the soil. The soil purifies the wastewater by removing the germs and chemicals before they reach the groundwater or any adjacent surface waters such as rivers, lakes, and estuaries. This however can only be achieved if the soil conditions allow for percolation at an acceptable rate. High ground water or rocky or clay type soils will preclude a proper Soak-away from being built. Other options will need to be considered here such as an above ground soak-away or a Biomite recycling plant which will clean the water and allow it to be used above ground for irrigation.