Cold Water Plumbing Design notes.pdf

Induction Course for new M&E Engineers 19  – 21 May 2014

Cold Water Plumbing Design

Ir. M. Saravanan Director Jurutera Perunding Inspirasi Sdn Bhd

COLD WATER PLUMBING DESIGN 1.

Rules and Regulations governing Cold Water Plumbing Design 

Local Authority requirements



British Standards 6700:1987



Guide to the Water Supply Rules and ‘Panduan Kaedah-Kaedah Bekalan Air’



Plumbing Engineering Services Design Guide (U.K.)



ASPE (American Society of Plumbing Engineers)



 



CP310:1965 – Water Supply SPAN ( Suruhanjaya Perkhidmatan Air Negara), New Water Supply Rules, Regulations and Uniform Technical Guidelines (UTG).

2.

Functions of various Firms and Organisations in Cold Water Design and Installations

2.1

Owner (i)

Decide on the type of buildings etc., residential apartments, office building, shopping complex to be built at selected location.

(ii)

Allocate budget for cold water plumbing installations and appoint various consultants for the proposed development.

(iii) Have their own project management team to liaise with all the relevant consultants. (iv) Award the contract of supplying, installing, testing and commissioning of cold water plumbing system to the successful tenderer upon recommendations from the M&E consultant. 2.2

Architect (i)

Leads a team of consulting engineers in completing the particular project.

(ii)

Prepares the complete set of preliminary architectural drawings that includes proposed locations and sizes of M&E rooms for cold water plumbing services.

(iii) Arrange technical meetings with M&E consultant to finalise the proposed locations and sizes of M&E rooms, etc., water tanks, pump rooms and plumbing shafts. (iv) Prepares final architectural drawings that includes all the relevant cold water plumbing services requirements.

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2.3

Consultants 2.3.1

2.3.2

2.4

Civil and Structural Consultant (a)

Responsible for the design of internal cold water reticulation system

(b)

Submits external water reticulation plans to the Local Authority and obtain approval.

Mechanical and Electrical Consultant (a)

Responsible for the design of internal cold water reticulation system and material specified for the plumbing system.

(b)

Submits internal water reticulation plans to the Local Authority for record.

(c)

Prepares tender drawings, tender document, tender report, construction drawings and certificate of payment for the supply, installation, testing and commissioning of cold water plumbing system.

(d)

Certifications of the all the inspections and testing on site and that the plumbing installation has been constructed in accordance with the submitted plans.

(e)

To submit form G5 ( Certificate of Compliance and Completion) CCC upon the completion of works to local authority.

Contractor (i)

The nominated contractor will undertake the responsibility of supplying, installing, testing and commissioning of cold water plumbing system.

(ii)

Prepares shop drawings, as-built drawings and operation & maintenance manual (O/M).

(iii) Arrange for authority inspection upon completion of the installation. (iv) To appoint the registered plumber( Permit Holder) to supervise and certify that all the plumbing installation works as been as carried out as per submitted drawings and as per SPAN requirements. 2.5

Authority (i)

Check the internal cold water reticulation drawings and issue the letter of denial (Surat penafian).

(ii)

Conduct inspection of the completed installation if necessary

(iv) Issue of water meters.

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3.

Cold Water System Design for Buildings

3.1

Plumbing Cold Water Terminology  Absolute Pressure

:

It equals the sum of the gauge pressure and the atmospheric pressure corresponding to the barometer.

 Air test

:

A test that is applied to the plumbing system upon its completion, but before the building is plastered.

 Ambient temperature

:

The prevailing temperature in the immediate vicinity or the temperature of the medium surrounding an object.

 Anchor

:

A device used to fasten or secure pipes to the building or structure.

Backflow

:

The flow of water or other liquid, mixtures or substances into the distributing pipes of a potable supply from any source or the source other than its intended use.

Black pipes

:

Steel pipe that has not been galvanised.

Burst pressure

:

Pressure which can be slowly applied to a valve at room temperature for 30 sec without causing rupture.

Bushing

:

A pipe fitting for connecting a pipe with a female fitting of larger size. It is a hollow plug with internal and external threads.

Butt weld joint

:

A welded pipe joint made with the ends of two pipes butting each other, the weld being around the periphery.

Cavitation

:

A localised gaseous condition that is found within a liquid stream.

Companion flange

:

A pipe flange to connect with another flange or with a flanged valve or the fitting. It is attached to the pipes by threads welding or other method and differs from a flange which is an integral part of a pipe of fitting.

Compression fitting

:

A fitting designed to a pipe or tube by means of pressure or friction.

Compression joint

:

A multi piece joint with cup shaped threads nuts which, when tightened, compress tapered sleeves so that they form a tight joint on the periphery of the tubing they connect.

Coupling

:

A pipe fitting with female threads only which is used to connect two pipes in straight line.

Elbow

:

A fitting that makes an angle between the adjacent pipes. The angle is 90.

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3.2

Erosion

:

The gradual destruction of metal or other materials by the abrasion action of liquids, gas solids or mixtures of these materials.

Expansion joint

:

A joint whose primary purpose is to absorb longitudinal thermal expansion in the pipe line due to heat.

Fitting

:

The connector or closure for the fluid lines and passages.

Fitting, compression

:

Fitting, flared

:

A fitting which seals and grips by manual adjustable deformation. A fitting which seals and grips by a performed flared at the end of the tube.

Fixture unit (Loading unit)

:

A measure of the probable hydraulic demand on the water supply by various types of plumbing fixtures. The supply fixture unit value for particular fixture depends on its volume rate of supply, on the time duration of a single supply operation and on the average time between successive operations.

Flow pressure

:

The pressure in the water supply pipe near the water outlet while the faucet or water outlet is fully opened and flowing.

Potable water

:

Water which is satisfactory for drinking, culinary and domestic purposes and meets the requirements of the health authority having jurisdiction.

Water hammer

:

The forces, pounding noises and vibration, which develop in a piping system when a column of non-compressible liquid flowing in the pipeline at a given pressure and velocity is stopped abruptly.

Standards applicable for Cold Water Plumbing System Design 

British Standards 6700:1997

British Standards Specification for design, installation, testing and maintenance of services supplying water for domestic use within buildings and their curtilages. 3.3

Computation of water demand for various types of building Three methods of consumption estimate normally practised are: (i)

Based on local water work authority requirements that are normally applied to housing estates, flats and hotels.& UTG by SPAN

(ii)

Based on Rule 224 (Uniform Water Supply Rules).

(iii) Based on actual recording of daily water consumption. This method is applied to hospitals, expressed in terms of gallons per bed.

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UTG (Uniform technical Guidelines) requires the minimum capacities of the storage cisterns to be as shown in Table 1 below: Table 1 Types of building Dwelling houses (rural) Low Cost Houses ( Rural and Urban) Dwelling houses and flats with individual storage (urban) Multi Storey flats with shared storage Semi-Detached/Bungalows Shop house( 1 Storey)/Low Cost Shop Shop house( Double Storey) Shop house ( 3 storey) Shp houses ( 4 storey)

Minimum nominal capacity 800 litres /unit 800 litres /unit 1300 litres /unit 1000 litres/unit 1500 litres/unit 2000 litres/unit 3000 litres/unit 4100 litres /unit 4550 litres/unit

If the capacity of a storage required cannot be obtained from Table 1, it should be calculated based on the figures given in Table 2 and the number of persons using/working/residing in the building would be the minimum storage capacity being equal to the quantity required for one day’s use. Table 2 Types of building Offices/Shopping complex/Commercial Community centres Hotels Hostels Day schools/kindergarden Boarding School Educational Institutions( day type) Educational Institutions with hostel Restaurant Hospital  Airport Wet market Dry market Light industrial Workshop Warehouse Mosque or other places of worship

Storage requirement 1000 litres/100 sq.m 1000 litres/100 sq.m 270 litres/person 180 litres/person 30 litres/person 180 litres/person 100 litres/student 250 litres/student 14 litres/person 1500 litres/bed 25 litres/passenger 1500 litres/stall 450 litres/stall 1500 litres/unit 1500 litres/unit 50 litres /person

When the number of persons using/working/residing in the building in not known, the capacity of the storage cistern can be estimated from the number of fittings installed in the building. The storage requirement for each fitting should be as given in Table 3 below:

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Table 3 Fittings Shower Slipper bath Water closet Lavatory basic Sink Urinal Bed pan washer Wash up sink 3.4

Storage requirement/fitting/day 450 –900 litres 910 litres 180 litres 90 litres 90 litres 180 litres 180 litres 225 litres

Tank sizing method and types of tank available in the market The total storage capacity of the suction and the storage cistern (elevated tank) should not be less than that required for one day’s use. Further, the suction cistern should not hold more than 1/3 the quantity of water for one day’s use nor should the cistern contain less than the quantity required for one-hour pumping without inflow into the cistern. Generally, the suction tank contains 1/3 of the total water demand and the elevated tank contains 2/3 of the total water demand. Capacity in relating to a cistern means the capacity measured up to the water level unless otherwise stated and is not a nominal capacity which is the volume calculated from the overall internal dimension of the cistern. It is to be noted that the effective tank capacity can be estimated by estimating the effective height as follows: Effective tank height = nominal tank height - *free board - minimum height above bottom of tank. *Free board = clearance above top water level inside the cistern. The free board level depends on the ballcock valve size: Ballcock valve mm 40mm and less 50 65 75 100

Free board (mm) 150 250 300 350 400

There are several types of tanks available in the market and these are listed below for reference: R.C. (reinforced concrete tanks)

1. These tanks are constructed mostly in basements and recommended when there is space constrain and odd space available for the water tanks. 2. The life span is estimated to be very long and no maintenance is required. 3. The cost is higher than pressed steel galvanised tanks. 4. HDPE lining is required

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3.5

FRP (fibre reinforced plastic) tanks

1. These tanks are popular now and vastly being used due to longer life span estimated at 25 years and minimal corrosion at bolted joints. 2. The cost is higher compared to the tanks mentioned above. 3. The maximum height allowed is 3 meter.

Poly tanks

1. These are the moulded tanks and available in standard sizes. 2. The cost is the cheapest compared to the types of tank mentioned above.

Introduction of various cold water system for buildings 3.5.1

Upfeed System Where the pressure in the water main is sufficient to distribute water throughout the entire building, an upfeed system such as shown in Figure 1 is used. The height of the building that may be served without pumps to boost the water pressure depends on the available pressure in the water main, the requirement of the fixtures and local authority requirement. The pressure available under non-flow conditions is called the static pressure. With water flow, there is a pressure loss due to friction as water flows through the pipes. Therefore, the residual pressure at the point of use under flow conditions is the static pressure minus the pressure loss due to friction.

3.5.2

Downfeed System (Gravity Feed System, Elevated Water Tank System) In an elevated water tank system, such as the simplified system shown in Figure 2, water is pumped from the water main to an elevated water storage tank located above the highest and most hydraulically remote point in the water supply system of the building. The height of the water tank provides additional static head, resulting in higher pressure in the water distribution system. For each 2.31 ft. (0.7m) elevation of the tank, there is an increase in the pressure of 1 psi (6.9 kpa).  An elevated tank system is made up of the following components: (i)

A suction tank that acts as a buffer tank or break tank between the elevated tank and public water main pipe. It is a requirement of the water works authority to prevent pressure fluctuations in the water main.

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(ii)

A gravity tank that stores water at atmospheric pressure.

(iii) Pumps that fill the tank by pumping water from its source. (iv) Controls that turn pumps on and off when the water inside the tank reaches the preset value. (v)

3.5.3

Alarms that alert operating personnel that a malfunction exists.

Pneumatic Direct Water System Pneumatic Direct Water System is basically designed for provision of drinking water for high rise buildings. Under the gravity feed system, all the water supplied to the various appliances including drinking taps come from the roof tank and there is a risk of the water in the roof tank becoming contaminated. Hence, it would be preferred to have drinking water supplied direct from the water main. However, for high rise buildings, the pressure in the main may not be sufficient to supply all the drinking water appliances and a pneumatic water system is used to overcome this problem.

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Besides the provision of drinking water, the pneumatic water system is also used when the pressure required at the appliances cannot be by gravity feed system. For example, certain appliances such as flush valves, bed pan washer or even an instantaneous water heater requires high pressure to operate satisfactorily. If these are located at the highest level of a building, the gravity feed system would not be able to provide the required pressure. The basic components of a pneumatic water system are:   

3.6

Suction tank Booster pump Pneumatic tank with or without air compressor

Sizing of Cold Water Supply Pipe In designing cold water supply installations, an assessment must be made of the probable maximum water flow. In most buildings, it seldom happens that the total number of appliances installed are ever in use at the same time and therefore, for economic reasons, it is usual for a system to be designed for a peak usage which is less than the possible maximum usage. The probable demand will depend upon the type of sanitary appliances, the type of building in which they are installed, and the frequency of usage. The Plumbing Institute has devised a method of assessing the probable maximum demand based upon the theory of probability. With this method, loading unit (fixture unit) rating has been devised for each type of sanitary appliance based on its rate of water delivery, the time the taps are open during usage and simultaneous demand for a particular type of appliance. Table 4 gives the rate of flow, pipe size, loading units and minimum pressure.

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Table 4 Appliances

Rate of flow (LPM/GPM)

Pipe size (mm)

Loading units

W.C. flushing Wash basin tap Basin spray tap Bath tap (20mm) Bath tap (25mm) Shower (nozzle) Sink tap (0.5) Sink tap (0.75) Sink tap (1.0) Flush valve

6.8/1.5 9.0/2.0 2.3/0.5 18.1/4.0 36.4/8.0 9.0/2.0 11.4/2.5 18.1/4.0 36.4/8.0 50/11

15 15 15 20 25 25 15 20 25 25

2 1.5 – 3.0 1.5 10 10 3 3 – 5 3 – 5 3 – 5 10

Minimum pressure (meter head)Commercial 7 7 7 7 8 8 8 8 8 10.5

By multiplying the number of each type of appliance by its appropriate loading unit and adding the results together, a figure for the total loading units is obtained which if applied to Figure 4 enables the recommended design flow rate to be read off.

Figure 4 – Loading units and design flow rates

It is best to determine the pipe size after the schematic drawings have been completed, as the whole system could be clearly seen. Two fundamental factors governing pipe sizing are velocity and frictional loss. Normally, velocity is limited to a maximum of 3.0 m/s and minimum 0.5 m/s. Friction rate is usually kept below 10m/100m.

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The design approach also varies between a down feed system and a pressurised system. For the downfeed system, frictional loss is always the controlling factor whereas velocity is always the factor to be considered in a pressurised system. The diameter of the pipe necessary to give a required flowrate will depend upon the head of the water available, the smoothness of the internal bore of the pipe and the effective length of the pipe. An allowance for the frictional resistance set up by fittings such as elbows, tees, taps and valves must be added to the actual length of the pipe. Tables 5 and 6 give allowance for fittings and draw off taps expressed in the equivalent pipe lengths. To determine the diameter of a pipe length must be calculated. A calculation sheet and a pipe sizing graph for cold water system are attached for reference. However, in certain situations like for the range of showers in a sports pavilion or the range of wash basins in a hostel, the pipework has to be designed for full flow as it is highly likely that all the appliances may be in use at the same time. Table 5 – Equivalent Pipe Lengths ( Copper, plastics and stainless steel) Bore of the pipes(mm) 12 20 25 32 40 50 65 73

Elbow

Tee

Stop Valve

m 0.5 0.8 1.0 1.4 1.7 2.3 3.0 3.4

m 0.6 1.0 1.5 2.0 2.5 3.5 4.5 5.8

m 4.0 7.0 10.0 13 16 22 5.5 34

Check Valve m 2.5 4.3 5.6 6 7.9 11.5 -

Table 6 – Loss of Head through Draw-off Taps and Equivalent Pipe Lengths Fitting (BS1010)*

½ in. pillar tap ½ in. bib tap ¾ in. bib or pillar tap 1 in. bib or pillar tap

Flow rate tap fully open

Loss of head

gal/min 2 2½ 4

ft 1.7 2.5 2.5

8

5.0

Equivalent pipe length Copper Galvanised mild steel ft ft 9 13 9 13 28 18 71

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*BS1010 – Draw-off taps and stop valves for water services (screwdown pattern)

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3.7

Sizing of booster pumps and hydro-pneumatic pumps 3.7.1

Booster pumps (transfer pump) Pumps should be sized to deliver the quantity of water required for one day’s use. Office building Residential building

3.7.2

6 – 8 hours 8 – 16 hours

Hydro-pneumatic pumps The pump flowrate shall be equal to or greater than the estimated maximum demand of the system. The discharge head of the pump is equal to the maximum pressure of the tank (P2). P2 = KP1 where K is the pressure ratio and P1 is the maximum pressure of the tank and P1 = static head of hydraulically furthest appliance + pressure drop in piping + pressure required at appliance. K

3.8

= 1.5 (optimum value)

Pumps and accessories Pumps are primarily of three types: centrifugal, reciprocating and rotary. The most commonly used pumps in residential and commercial buildings are centrifugal pumps. Centrifugal pumps used in plumbing systems are classified on the basis of internal casing design as volute or regenerative (turbine). On the basis of the main direction of discharge of liquid, impellers are classified as radial axial or mixed flow. The most commonly used centrifugal pumps are as follows:    

End suction centrifugal pump Vertical multi stage pump Horizontal split casing pump Vertical split casing pump

The performance curve is the easiest and most satisfactory way to show graphically the relationship between head, capacity, horsepower, etc. of any pump.

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The line sloping from left to right represent the varying quantities of liquid delivered by the pump with variations in head. The intersection of this line with the zero delivery line shows the ‘shut off head’ or pressure developed by the pump when the discharge valve is shut. The curve showing the horsepower to drive the pump slopes upward in the opposite direction, with the lowest point at the shut-off pump. These two lines show the complete performance of the pump for the one speed for which the curve is plotted. Another curve showing the efficiency of the pump is usually plotted on the same sheet. This efficiency curve shows the amount of usable work done by the pump in percentage of power delivered to the pump shaft. 3.9

Water hammer Water hammer is a pulsating type of noise which may, on occasion, be heard emanating from a pipework installation. The noise is caused mainly by shock waves which are set up when water, which is flowing at high velocity, is suddenly arrested. The practical conditions which can create this adverse effect are the too rapid closure of manual valves, or the virtual instantaneous closure of automatic control valves. Pumped pipe water supplies are also liable to water hammer if provision is not made at the design stage. Plumber type pumps for example give a pulsating type of discharge which may require damping out. Cases have occurred of water hammer damage although little audible sound was present. Premature failure of valves, joints and the loosening of supports and clips are common examples of such damage. Gravity water installations do not, as a rule, give rise to the problem but when water velocities exceed 3 m/s, water hammer conditions may exist. The increasing use of pressurized domestic water system in the U.K. could well lead to an increase in the incidence of water hammer if proper precautions are not taken at the design stage.

4.

Cold Water Plumbing Materials

4.1

Copper tubing Copper tubing which is manufactured from 99.9% pure copper. Plumbing copper tube is manufactured in four different wall thickness or types K, L, M and DWV (drainage, waste and vent). Type K copper tubing has the heaviest wall thickness. Copper tube should comply with BS 2871 Part 1 (Table X) or ASTM B88 (American Standard).

4.2

Plastic pipes PLASTIC pipes, or more accurately, thermoplastic pipes, have been in use in plumbing applications since the late 1970s. There are several thermoplastics that are being used for the plumbing services such as ABS,HDPE,PVC and PPR . Thermoplastics can be sub-divided into two main categories, i.e Amorphous and Crystalline. Amorphous material uses bonding agents such as ABS Solvent Cement, while Crystalline uses heat such as HDPE butt/Electro Fusion.

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4.3

Plumbing valves 4.3.1

Gate valve The gate valve provides a straight through passage for the flow of fluid. The valve is used extensively where uninterrupted flow is required with minimum pressure drop. It is not recommended for regulation and should only be used in fully opened or fully closed position.

4.3.2

Globe valve The valve is designed to stop or regulate the fluid flow. Ideal for regulating because wear by erosion around the seating is evenly distributed. Positive closure. High pressure drop due to tortuous flow path.

4.3.3

Check valve Frequently called a non-return valve or reflux valve, this valve is self-acting and prevents reversal of flow. The swing type and the lift type check valves are most commonly used.

4.3.4

Ball valve There are two basic forms of ball valves, the floating ball and trunnion mounted ball. It has 90 dg turned operation and is relatively compact.

4.3.5

Butterfly valve Quick operation. Good regulating characteristics. Temperature limited by seating material on resilient seated types. Metal-to-metal seated type does not give tight shut-off. Disc mechanism always in fluid flow.

4.4

Water meters The water meter is installed at the end of the water service pipe, either directly inside or outside of the building walls, in accordance with local plumbing code restrictions. Three types are installed by the plumber as follows: (i)

Disk meters

:

A disk meter is used for measuring the flow of water through small water services and are available in sizes from 5/8 inch to 2 inches.

(ii)

Turbine meters

:

A turbine meter is used in buildings in which water is used in large and constant volume and is available in 2, 3, 4 and 6 inch sizes.

:

A compound meter is a water meter that unites a disk and a turbine meter in one body. Compound meters are made in 2 to 10 inch sizes for use in buildings in which there is large fluctuation in water flows.

(iii) Compound meters

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5.

Joining, Installing and Supporting Pipes

5.1

Galvanised steel threaded joints Screwed joints in steel piping shall be made with screwed socket joints using wrought iron, steel or malleable cast-iron fittings. A thread filler shall be used (PTFE tape or proprietary sealants). Exposed threads left after jointing shall be painted or, where installed underground, thickly coated with bituminous or other suitable corrosion preventative in accordance with BS 5493. Since all pipe fittings are tapped with the internal (female) pipe thread at the factory when they are manufactured, the plumber need only make the external (male) pipe thread. The vertical piping must be secured at sufficiently close intervals to keep the pipe in alignment. Therefore, it is recommended to support the pipe at each storey in height. The horizontal pipe shall be supported at 12 foot intervals. It is a common practice in plumbing installation that for pipe sizes 3 inches and below, screw and socketed  joints are used and for pipe sizes above 3 inches, flange joints are used,

5.2

Copper tubing joints The three most common methods of joining copper tubing that a plumber will use are the solder joint with capillary fittings, the flared joint, and the compression joint. Solder  joints are used on water lines and drainage lines. The flared joints are commonly used on underground water supply tubing. The compression is most commonly used on the exposed water supply tubing to plumbing fixtures. Solder joints depend on capillary drawing free-flowing molten soldered into the gap between the fitting and the tube. The vertical piping must be secured at sufficiently close intervals to keep the pipe in alignment. Therefore, it is recommended to support the pipe at each storey in height. The horizontal pipe shall be supported at 10 foot intervals.

5.3

Plastic pipe joints The various types of plastic pipes and fittings are joined together with one of three methods, depending on the physical use to which the particular plastic piping will be put. The three methods used by plumbers to join plastic pipes and fittings are: (i) The solvent weld joint. (ii) The insert fitting joint. (iii) The flare fitting joint.

6.

Testing and Inspecting the Plumbing System The air test of water supply piping is made by attaching an air compressor to any suitable opening and closing all other inlets and outlets to the system with the appropriate pipe cap of plug, or with testing plugs. Water supply and distribution piping is normally tested at 1½ times the working pressure or 150 psig, whichever is greater. The test period is usually 12 to 24 hours.  A hydrostatic test is a test in which the pipe being tested is filled with water and submitted to additional water pressure. A hydrostatic test is the common test for water main and water service piping. The procedure for applying a hydrostatic test is

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to fill the pipes being tested completely with potable water (after sealing all openings) and then to force additional water into the pipes with a hydrostatic test pump. Since the testing of plumbing systems is a very important part of the plumber’s work, the apprentice should become acquainted with the procedure that is followed for all plumbing tests. The procedure for all plumbing test follows the eight points listed below: (i) (ii) (iii) (iv) (v) (vi) (vii) (viii)

Assemble the testing apparatus. Seal all openings. Apply the test. Check for leaks. Fix defects. Call for an inspection and test. Assist the inspector at time of test. Remove testing apparatus on completion of test and inspection.

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Appendices  Appendix E : Pipe Sizing Calculations ( BS 6700 : 1987). Pipe Sizing Graph for ABS Class 12 and Class 15. Sample of Standard Forms from SYABAS for internal plumbing. SPAN announcement for approval of internal plumbing.

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