Intake structures, pipes, joints, valves and pumps

INTAKE STRUCTURES

Intake structures are used for collecting water from the surface sources such as river, lake, and reservoir and conveying it further to the water treatment plant. These structures are masonry or concrete structures and provides relatively clean water, free from pollution, sand and objectionable floating material.

Site Selection for Intake Structures

• The site should be so selected that it may admit water even under worst condition of flow in the river. Generally, it is preferred that intake should be sufficiently below the shore line.
• Site should be very close to treatment plant as possible.
• It should be so located that it is free from the pollution. It is better to provide intake at upper stream of city so that water is not contaminated.
• It should not interfere with river traffic, if any.
• It should be located where good foundation conditions are available.
• It should be so located that it admits relatively pure water free from mud, sand and pollutants i.e, it should be protected from rapid currents.

Types of Intake Structures

Intakes are classified under three categories:

Category 1:

1. Submerged intake
2. Exposed intake

Category 2:

1. Wet intake
2. Dry intake

Category 3:

1. River intake
2. Reservoir intake
3. Lake intake
4. Canal intake

Submerged Intake Structures

1. It is the one which is constructed entirely under water.
2. It is commonly used to obtain supply from a lake.

Exposed Intake Structures

1. It is in the form of a well or tower constructed near the bank of a river, or in some cases even away from the river banks.
2. Exposed intakes are more common due to ease in operation.

Wet Intake Structures

1. It is a type of intake tower in which the water level is practically the same as the level of the sources of supply.
2. It is sometimes known as Jack well and is most commonly used.

Dry Intake Structures

1. In case of dry intake there is no water in the water tower.
2. Water enters through entry port directly into the conveying pipes.
3. It is simply used for the operation of valves etc.

River Intake Structures

1. It is a type of intake which may either located sufficiently inside the river so that demands of water are met with in all the seasons of the year, or they may be located near the river bank where a sufficient depth of water is available.
2. Sometimes, an approach channel is constructed and water is led to the intake tower.
3. If the water level in the river is low, a weir may be constructed across it to raise the water level and divert it to the intake tower.

Reservoir Intake Structures

1. When the flow in the river is not guaranteed throughout the year, a dam is constructed across it to store water in the reservoir so formed.
2. These are similar to river intake, except that these are located near the upstream face of the dam where maximum depth of water is available.
3. Design of intake may vary based on the type of dam.

Lake Intake Structures

1. Generally submerged intakes are preferred for lake intakes.
2. These are constructed as cribs or bell mouths. The cribs are made of heavy timber frame work which is partly or wholly filled with rip-rap to protect the intake conduit against damage by waves etc.
3. The top of the crib is covered with cast iron or mesh grating.

Canal Intake Structures

1. In some cases, source of water supply to a small town may be an irrigation canal passing nearer or through the town. It is to be constructed in such cases.
2. Generally it consists of masonry or concrete intake chamber of rectangular shape, admitting water through a coarse screen.
3. A fine screen is provided over the bell mouth entry of the outlet pipe.
4. The intake chamber may be constructed inside the canal bank if it does not offer any appreciable resistance to normal flow in the canal.
5. It’s preferred to provide lining to the canal near the intake chamber.

PIPES

SEVEN TYPES OF PIPES USED IN WATER SUPPLY SYSTEM OF BUILDINGS
Pipes which are commonly used in water supply system are given below.

1. Cast Iron (CI) Pipes
2. Steel Pipes
3. Galvanized Iron (GI) Pipes
4. Copper Pipes
5. Plastic or Polythene or PVC pipes
6. Asbestos Cement (AC) Pipes
7. Concrete Pipes

CAST IRON PIPES
These pipes are most commonly used in water distribution system mainly because of the following reasons.

1. They are cheaper in cost
2. It has high resistance to corrosion
3. It is highly durable
4. C.I. pipes are manufactured by following 4 methods.
1. Horizontally cast (MC ware pipes)
2. Vertical cast (pit cast in sand moulds)
3. Centrifugally cast in sand lines moulds spun type
4. Centrifugally cast in water cooled metal moulds

Now a days horizontally cast C.I. pipes are no longer used.
Centrifugally cast pipes posses fine grained dense structure and uniform thickness and therefore they are widely used. Special care has to be taken during transportation and making connection of these pipes, to prevent damage.

STEEL PIPES
Use of steel pipes in water supply system is suggested when pipes are subjected to very high pressure (i.e. above 7 kg/cm2) large diameter pipes are required
Steel pipes are used because they are stronger and lighter in weight as compared to C.I. pipes. These pipes, however, require adequate preventive measure to sustain adverse atmospheric conditions.
When steel pipes are encased in cement mortar or cement concrete, they are called Hume Steel pipes.

GALVANIZED IRON (GI) PIPES
This type of pipe is used for water supply work inside the building. These pipes are wrought steel pipes provided with zinc coating. They are available in light, medium and heavy grades depending on the thickness of the metal. For a 15 mm GI pipe, the thicknesses are 2.0, 2.65 & 3.25 for the light, medium and heavy grades, respectively. Generally the medium grade pipes are used for internal plumbing in building. Mostly screw and socket joints are used for G.I. pipes.

COPPER PIPES
These pipes are used in hot water installation. They have high tensile strength and can therefore have thin walls and they can be bent easily. Copper pipes are sometimes coated with chromium to enhance its appearance.

PLASTIC OR POLYTHENE OR PVC PIPES
These pipes are being used increasingly these days for supply of cold water in external and internal plumbing work. They are light in weight, non-corrosive, lower in cost and do not require any threading for connections. There are 3 common types of plastic pipes are available in market, as
given below.

1. Unplasticized PVC (UPVC) or rigid pipes for use with cold water
2. Plasticized PVC pipes which are plasticized with addition of rubber. 
3. It has lower strength and lower working temperature than UPVC pipes.
4. Chlorinated PVC (CPVC) pipes which can withstand higher temperatures upto 1200 (used to carry hot water)
5. For pipes used in soil and waste water discharge systems, the thickness of the wall will be larger than that of used for roof drainage.
6. Rigid PVC pipes are used for distribution of water with temperature below 450C. At higher temperature, the strength of the pipes decreases. Similarly ultraviolet radiation from sunlight as well as frequent changes in temperature reduces the life of PVC pipes.
7. These pipes are costlier than AC pipes but cheaper than GI pipes.

 ASBESTOS CEMENT (AC) PIPES

1. These pipes are used for drainage of rainwater from roofs, soil and waste and also for ventilation. 
2. They come in two profiles – one with beading around socket (WB) and the other without beading around socket (WOB). The latter type is more common than the former. 
3. The pipes come in lengths of 3 meters. 
4. The principal defects of these pipes are that they are heavy and they break easily. 
5. These pipes are cheaper than PVC pipes.

CONCRETE PIPES

1. Un-reinforced pipes of small diameters as well as reinforced and  prestressed concrete pipes of large diameters are available for water supply and other uses.
2. Small un-reinforced concrete pipes are very much used for drainage of rain water.
3. Large diameter pipes are generally used for major water supply works.

JOINTS

Pipe joints in water supply are major components of plumbing system provided to connect multiple pipes. There are several types of pipe joints, but their selection depends on pipe sizes, material and flow pressure etc. Pipe joint provided should withstand pressure of each pipe. Types of Pipe Joints used in water supply are discussed below:

1. Threaded joint
2. Brazed joint
3. Soldered joint
4. Welded joint (butt welded, socket welded)
5. Flanged joint
6. Compression joint
7. Grooved joint

Threaded Joint in Pipe

1. Threaded joint pipes are connected by screwing with the help of threads provided for each pipe. One pipe having internal threads and the other one having threads externally. 
2. Cast iron pipes, copper  pipes, PVC and G.I pipes are available with threads.
3. Threaded joints are available from 6mm diameter to 300mm diameter pipes. They are preferable for low temperature areas and low pressure flows. 
4. In the areas of high temperature, the joints may expand and leak due to thermal expansion. Installation of threaded joint is easy however, regular maintenance is required.

Brazed Joint in Pipe

1. Brazing is the process of jointing pipes using molten filler material at above 840 C. 
2. Brazing is generally used for joining copper pipes or copper alloy pipes. 
3. The filler material majorly consist tin which has great affinity towards copper. However, because of its weak property, tin is added to other materials like nickel, bismuth, silver and copper. 
4. The melting point of parent metal should be higher than filler metal. 
5. Mechanical strength of brazed joint is low compared to other joints. 
6. This type of joint is suitable in moderate range of temperature areas.

Soldered Joint in Pipe

1. Soldering is also similar to brazing but the only difference is in case of soldering the filler metal melts at below 840 C. 
2. Soldering also used to joint copper and copper alloy pipes. 
3. Before soldering, flux called paste is applied to pipes and fittings to prevent them from oxidation from flame. 
4. Soldering requires skilled workers for installation. 
5. Soldered joints are suitable for low temperature areas. 
6. These joints have low mechanical strength as brazed joints.

Butt Welded Joint in Pipe

1. When the pipes are of same diameter butt welding is to done to join the pipes. It is the most common type of welding. 
2. Skilled workers are required to install the butt welded joint. 
3. These joints are generally used for large commercials and industrial piping systems. 
4. Butt weld provides good strength for the joint and it can resist high pressure because of smooth and continuous surface inside the joint. 
5. Butt weld joints are expensive, to make it economical sometimes internal weld backing rings are used, which joins the pipe with less amount of filler material. 
6. Rings may fail under heavy stress and cracks are developed. 
7. The joints are fixed and cannot be opened for maintenance purposes. 
8. External smoothing of welded portion gives a good appearance to the piping system.

Socket Welded Joint in Pipe

1. Socket welded joints are used wherever there is a high chance of leakage in joints. 
2. Pipes are connected as putting one into other welded around the joint. 
3. Pipes having different diameters are suitable for this type of joint. 
4. For pipes having same diameter, required fittings are used. 
5. Welding cost is generally lower than butt welding. 
6. Fatigue resistance is lower for socket welded joints when compared to butt weld joints.
7. Socket welded joint gives good results when compared with other mechanical joints.

Flanged Joint in Pipe

1. Flanged joints are used for high pressure flows and for large diameter pipes. 
2. They are used for plain end pipes or threaded pipes. 
3. Two flange components are connected by bolts at the pipe joint to prevent leakage. 
4. Generally these are made of cast iron, steel etc. these have good strength and do not fail against high pressure. 
5. Against high temperatures the bolts may fail under creep and lose their grip so, fixing of bolts should be done properly while installing. 
6. They are useful for repairing pipelines and maintenance purposes.

Compression Joint in Pipe

1. When the pipes have plain ends they are joined by installing some fittings at their ends then that type of joint is called compression joint. 
2. Pipe ends are fitted with threaded fittings or couplings to connect them.
3. In this case pipes of different materials and different sizes can be connected. However, the joints should be properly fitted to resist flow pressure otherwise they may fail and leakage may occur.
4. Compression fittings are available in different materials and selection of fittings may depend upon specific requirements.

VALVES

Valves are used to control and regulate the flow of water. The different valves used in water supply are listed below:

Gate Valve

1. Gate valves could possibly be the most used valve in plumbing applications. 
2. Gate valves control water flow by raising or lowering an internal gate preventing the water from flowing into the other side.
3. Gate valves usually have a know at the top of a gate that raises or lowers the gate. 
4. Gate valves should never be used to reduce the pressure flowing into the pipe. 
5. They are very reliable and easy to install.

Ball valves are another reliable valve used widely in plumbing applications. Ball valves have a ball with a hole, that once open allows water flowing into the pipe. When the ball valve is closed, the hole is perpendicular to the pipe, preventing water from entering the pipe.

• Ball valves

1. Ball valves are operated through a lever handle, that when parallel to pipe indicates that the valve is open, so the handle will serve as a visual aid so you know that the water is flowing in the direction of the handle. 
2. When the ball valve is closed it forms an excellent seal, although no water control can be obtained when using ball valves.

• Globe valves

1. Globe valves are used to regulate flow in plumbing applications.
2. Globe valves are usually installed when the flow of water needs to be regulated or when it needs to be adjusted regularly. 
3. They contain a stopper that is raised and lowered by a knob on a shaft, that seals into a baffle to stop the flow. 
4. Globe valves get their name from the globe-like or ball-like appearance that the body of the valve has. 
5. A globe valve can be used to regulate flow in a plumbing line.
6. They are the best choice when the flow needs to be regulated or when the flow doesn't have to be fully open.

• Check valves 

1. Check valves are used normally in water tanks and other water storage applications. 
2. This type of valve has one inlet, where water comes in, and the outlet or the side where the water goes out. 
3. These valves allow the water to travel in only one direction. 
4. Check valves normally will prevent water flowing in the opposite direction as water would normally move. 
5. Back-flow preventers are also considered as check valves.

• Pressure reducing valves 

1. Water pressure reducing valves are installed to reduce the water pressure to the desired or accepted limits. 
2. They normally have a spring and diaphragm that is adjusted to certain limits depending on the pressure of the water being served. 
3. They can be installed in copper, PVC and other different pipe types. 
4. They normally last more than 10 years when maintained properly

• Butterfly valves 

1. Butterfly valves have a disc allowing the flow of water to be regulated. 
2. Butterfly valves, the manner in which they are manufactured, will normally reduce the pressure after the valve. 
3. Water flow can be precisely adjusted through butterfly valves. 
4. One of the most important drawbacks is that the gasket inside the valve can present maintenance issues after a couple of years.
5. When the butterfly valve is open, it can be observed that the disc is parallel to the pipe and when closed the disc is perpendicular to the pipe.​

• Air release valve

1. Air release valves are installed at each high point of a pressure pipeline. 
2. Air release valves are installed to eliminate or mitigate the water hammer issues, as they protect the pipelines against internal pressure. 
3. Air pockets will be released when the internal pressure exceeds specify limits, protecting the pipeline from pressure damages. 
4. These valves can be installed in copper and ductile iron pipes through a small penetration and fitting installed on the pipe.

• Angle valves 

1. Angle valves are typically installed at the water intake of plumbing fixtures or appliances
2. Angle valves could fail when high pressure is detected on the line. 
3. They are used to shut off water

PUMPS

Pumps can broadly be classified as:

1. Dynamic pumps and
2. Positive displacement pumps

Dynamic pumps are further classified into:

1. Centrifugal pumps
2. Vertical centrifugal pumps
3. Horizontal centrifugal pumps
4. Submersible pumps
5. Fire hydrant systems

Centrifugal pumps are most commonly used worldwide. The working is very simple, described well and carefully tested. This pump is strong, efficient and fairly cheap to make. Whenever the pump is in action, then the fluid pressure will increase from the inlet of the pump to its outlet. The change of pressure will drive the liquid throughout the system. This kind of pump produces an enhancement within force by transmitting mechanical power from the electrical motor to the liquid throughout the revolving impeller. The liquid enters the center of impeller and exits along the blades thereby enhancing the velocity of the fluid.

Vertical centrifugal pumps are also called cantilever pumps. This pump utilizes no filling container to cover the shaft. It uses a throttle bushing

Horizontal centrifugal pumps include a minimum of two or more impellers. All the phases are in a similar shelter and mounted on a similar shaft. Every stage enhances the head by an equal amount. Upto eight additional stages can be added.

Submersible pumps are also named as stormwater, sewage, and septic pumps. The applications of these pumps mainly include building services, domestic, industrial, commercial, rural, municipal, & rainwater recycle applications. These pumps are apt for shifting stormwater, subsoil water, sewage, black water, grey water, rainwater, trade waste, chemicals, bore water, and foodstuffs. 

Fire hydrant pump systems are also named as hydrant boosters, fire pumps, & fire water pumps. These are high force water pumps intended to enhance the capacity of fire fighting of construction by increasing the force within the hydrant service as mains is not sufficient. The applications of this system mainly include irrigation as well as water transfer.