SANITARY SYSTEM

SANITARY SEWER SYSTEM

Figure 1: Flushing water closet (Source: What's up Fagans?)

The most contact we have with the sanitary system is simply flushing a water closet or pulling out a plug in a wash hand basin. However, we tend to always forget the existence of sanitary system in our buildings despite its importance to ensure that the environment we live in is safe and clean.

Figure 2: Sanitary Sewer System in a building (Source: DS Plumbing)

A sanitary sewer system refers to a complex network of pipes and pumps that is both provided in a building and buried beneath the street. This system is designed to collect and convey the wastewater or waterborne wastes out of the buildings and transport them from homes, shop houses or industries to the treatment facility. Don’t get confused with the following terminology!

• Sewer – a pipe or conduct for carrying sewage and other liquid waste.
• Sewerage – the works required to collect, treat and dispose sewage including the sewer system, pumping stations, and treatment work.
• Sewage – any liquid-borne waste (include liquids containing chemicals in solution, ground surface or storm water) is admitted into or passes through sewers.
• Sewage disposal system – a system for disposing of sewage, by means of a septic tank, or by mechanical treatment, which is designed to serve a single building or a group of buildings independently of the public sewer.

Figure 3: Sewer, Sewerage, Sewage

The purposes of sanitary and sewer systems are as follow:

• ·       To maintain clean and healthy conditions within a building.
• ·       To collect and dispose waste materials as fast and early as possible in a systematic way.
• ·       To avoid the entry of foul gases from the sewer of the septic tank.

There are two types of drainage system for sanitary and sewerage, namely the drainage system above ground and below ground.

ABOVE GROUND DRAINAGE

*A stack is the main vertical pipe that carries away discharge from water closets and urinals (soil water) or other clear water waste from equipment and non- sanitary fixtures (waste stack). The design of the stack depending on the volume of the sanitary fittings the rate of flow out of the drain into the stack, the diameter of the stack and the type of stack fitting.

Discharge pipes consist of single stack, branching and vent pipe. Single stack pipe is installed vertically to ease the discharge of soil and waste water. Branching pipe is connected to sanitary fitting with single stack pipe. Vent pipe releases compressed air.

There are 3 types of above ground drainage systems employed in the installation of soil and waste water discharge pipes:

1. Single stack system

System where only single pipe (can act as BOTH soil pipe and ventilation pipe) is required. Stack is located inside or outside the external wall of the property and terminates roof eaves level with a cage or perforated cover. Discharge in branching pipes from sanitary fittings are transferred to single stack pipe where it is then drained into the drainage pipe. There is no ventilation pipe needed because stack itself is large enough to prevent pressure fluctuation (it itself can function as a vent pipe). This system is so far the most commonly used in domestic buildings as it is easy to install besides its significance in reducing the cost of soil and waste systems. However, the sanitary fitting should be installed near the single stack pipe separately to reduce the length of the branching pipe and minimize the sound of the flow in the pipe.

Figure 4: Single stack system (Source: Inazarina Ady- Sanitary Pipework)

2. One pipe system @ Single pipe system

One pipe system means 2 stacks in a system. In this system, all soil water (excreta) and waste water (sullage) discharge into one common pipe instead of using two separate pipes, meaning that all sanitary fittings are connected to only one pipe. Ventilation pipes are fitted to each discharge branch (but not each appliance) near to the bend to remove compressed air at this point.  All branch ventilating pipes drain into one main ventilating pipe. This system largely replaces the two pipes system and let itself very well to the use in multi-storey developments. It is far more economical than the two pipes system for a large number of sanitary appliances in ranges. All sanitary fittings should be installed near a main pipe.

Figure 5: Single pipe system (Source: Inazarina Ady- Sanitary Pipework)

3. Two pipes system @ Dual pipe system

This is the oldest system of plumbing. Two sets of vertical pipes, one for soil water as soil pipe (soil discharge pipe) and another for waste water as waste pipes (waste discharge pipe). The soil pipes receive the discharges from soil appliance (soil water from WC and urinals) and deliver it direct to the underground drainage system; The waste pipes collect the wastewater from shower tray, WB and bathtub then convey this to the ground level where it is delivered above the water seal in a trapped gully connected to the drainage system. The soil water and waste did not combine until reach the below ground drainage. The soil pipes as well as the waste pipes are separately ventilated (individual ventilation system), by providing, separate vent pipe or anti-siphon age pipe. It has 4 stacks in a system. This system is suitable when the waste fitting is located far from the waste water fitting.

Figure 6: Dual pipe system (Source: Inazarina Ady- Sanitary Pipework)

BELOW GROUND DRAINAGE

1. Separate drainage system

System in which the waste water and storm water are always kept separated. Two separate sets of sewers are installed, one for collection and conveyance of sanitary sewage and other for storm water. When a separate system is used, the sewerage treatment plant will not get overloaded in periods of wet weather. It is comparatively favoured by the local authorities as the installation and running costs of the sewerage treatment plant can be reduced.

Figure 7: Separate drainage system (Source: Winnipeg)

Advantages of separate drainage system:

• ·       Size of sewers required is smaller
• ·       Since the waste water and the storm water flows in separate pipes, the quantity of sewage to be treated is lesser.
• ·       As the sewers are smaller in sections, they can be easily ventilated.
• ·       During disposal, if the sewage is to be pumped, the separate system is cheaper.
• ·       Rain water can be discharged to the streams without any treatment.

Disadvantages of separate drainage system:

• ·       Since the sewers are of smaller size, it’s more difficult to clean them.
• ·       They are likely to get chocked.
• ·       Initial cost is high, when two separate set are used.
• ·       Maintenance cost of the sewers is also high.
• ·    Generally self-cleaning velocity is not available due to small quantity of sewage therefore, flushing is required at various point.

 2.  Combined drainage system

System in which some or all the storm water joins the waste water drainage system. This means that both surface water and foul water will be discharged into the sewerage treatment plant. In order to avoid the treatment plant being overloaded, it may be possibility to extract some foul water at various points in the drainage network. This can be achieved if the surface water is less dense than the foul water and tends to flow on the top in a drain. A separating device can be used to diver the surface water into a storm water channel or drain.

Figure 8: Combined drainage system (Source: Winnipeg)

Advantages of combined drainage system:

• ·       Both domestic sewage and storm water are carried in a single sewer, so construction cost is minimized.
• ·       The strength of domestic sewage is reduced because of the dilution of storm water.
• ·       The sewers are of larger size, therefore the chances of their chocking are rare, it is easy to clean them.

Disadvantages of combined drainage system

• ·       Initial cost is high due to the larger dimensions of sewers.
• ·       Due to larger dimensions of sewers, handling and transportation is comparatively harder.
• ·       Due to inclusion of storm water, the load on treatment plant increases.
• ·       During heavy rain the sewer may be overflow and may thus create unhygienic conditions.
• ·       It is uneconomical if the whole sewage is to be disposed by pumping.

PIPE GRADIENT

• All above ground and below ground horizontal drainage pipes should be laid to an adequate gradient.
• The fall in a pipe may be defined as the vertical amount by which the pipe drops over a distance.
• Gradient = Fall / Distance
• Gradients from 1 in 40 to 1 in 110 will normally give adequate flow velocities.
• A gradient of 1 in 80 is suitable for commencing calculations for pipe schemes. 
• If the gradient is not less than 1 in 40, then the pipe could block, as the liquidated waste flow out too fast leaving the solids slow down and become stranded.

Figure 9: Fall & Gradient in drainage pipe (Source: Drainage Consultant Ltd)

TRAP

Figure 10: Typical trap (Source: Wikipedia)

All appliances connected to the drainage system must have a trap on them to prevent the entry and penetration of any foul gases into the buildings. Basically, the materials used for trap are plastics and metals. There are different types and shapes of the traps matching their own functions.

Figure 11: Types of trap according to shapes (Source: Pelagan)

SANITARY FITTINGS

Various types of pipe fittings are available in plumbing systems for different purposes and functions. A pipe fitting is used in plumbing system to join multiple pipes of same size or different sizes, to regulate the flow or to measure the flow. They are made up of different materials like copper, iron, brass, PVC etc.

1. Shower   
      

                                                         

Figure 12: Shower (Source: Google) 2. Basins Figure 13: Basin (Source: Google) 3. Bath tub

Figure 14: Bath tub (Source: Google)

4. Urinal Bowl

Figure 15: Urinal Bowl (Google)

5. Water closets (WC) 

Figure 16; Water closets (Source: Saudi Ceramics)

6. Bidet

Figure 17: Bidet (Source: Groupon)

7. Sinks

Figure 18: Sinks (Source: The Home Depot)                                                      

CASE BUILDING INPUTS

Our case building chosen is the Pusat Kesihatan Universiti Teknology Malaysia (PKU, UTM). The following are the examples of the sanitary appliances found in this case building.

Figure 19 : Water basin (Source: PKU, UTM)

Figure 20: Water Closet (Source: PKU, UTM)

Figure 21: Water Hose (Source: PKU, UTM)

ESSENTIAL OF GOOD APPLIANCES

• Cleanliness- strong, smooth, non-absorbent and non-corroding surfaces, largely self-cleansing and permitting easy cleaning.
• Simplicity- for design and construction.
• Accessibility- can function for many work
•  Durability- with standing hard wear
• Economical- in terms of initial and maintenance cost
• Appearance – satisfactory

COMPARISON

Difference Between WATER SUPPLY SYSTEM and SANITARY SEWER SYSTEM

Water Supply System	Sanitary Sewer System
Treated water is transferred using water pipes	To drain the water that has been used
Serves to delivers clean water supply	To collect and remove waste matter systematically
To access all water supply at place who need clean water especially in house, hospital, school and etc.	To avoid the entry of foul gases from the sewer or the septic tank

SO... That's all about sanitary sewer system. Next week we'll be discussing more on SOLID REFUSE DISPOSAL!
SEE YOU NEXT WEEK!

Figure 12: Shower (Source: Google)

2. Basins

Figure 13: Basin (Source: Google)

3. Bath tub

Water Supply System

Sanitary Sewer System

Treated water is transferred using water pipes

To drain the water that has been used

Serves to delivers clean water supply

To collect and remove waste matter systematically

 To access all water supply at place who need clean water especially in house, hospital, school and etc.

To avoid the entry of foul gases from the sewer or the septic tank