Cold and Hot Water System

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Table of Contents

1. Introduction

2. Cold Water Systems in Malaysia

2.1 Cold Water Supply Systems

2.1.1 Direct Supply System

2.1.2 Indirect Supply System Types of Storage Tanks

3. Hot Water Systems in Malaysia

3.1. Solar Water Heater in Malaysia

4. Pipe Material Selection

4.1. Stainless Steel (SS)

4.2. High Density Polyethylene (HDPE)

4.3. Polypropylene Random Copolymer (PPR)

5. Pipe Sizing Guide

6. Our M&E Consultant Solutions

1. Introduction

Cold water and hot water supply systems are elementary systems that are present in every building. M&E consultancy for cold and hot water supply systems includes the design of the pipe route, the pipe size, location of water tanks and sizing of pumps.

2. Cold Water Systems in Malaysia

In Malaysia, incoming water source from the water company passes through the water meter. Then it runs directly to the water storage tank, usually located on the roof of the house. There is also a pipe that runs directly to the wet kitchen of a house from the water meter [1].

If the building is tall and the water supply pressure is insufficient to supply water to the top of the roof, there will be a suction tank located in the basement. A transfer pump will pump water from the suction tank to the rooftop tank. For areas where low water pressure is present, a hydro pneumatic pump can be used to increase the pressure at the pipe fitting.

2.1 Cold Water Supply Systems

There are two methods to supply water to a building: a direct supply system and an an indirect supply system.

2.1.1 Direct Supply System

Figure 1: Direct supply system simple installation schematic [2].

Direct supply systems do not have a water storage tank in the building. Water is fed directly from the supply mains of the water utility company to the pipe fittings within the building as shown in Figure 1.

Typically, this method provides water immediately for drinking and cooking because water that passes through a storage tank may be polluted. Because this system does not require additional pumps or storage tanks, it is less expensive and simpler to install.

Having access to clean drinking water due to the likelihood of bacterial contamination is considerably diminished because a water tank is absent. However, this system is only feasible for buildings with no more than two levels.

This system is considerably noisier than the indirect supply system because of the higher water pressure. At times of peak water demand, the supply and pressure of the water may also be impacted. Therefore, the direct supply system suffers from pressure fluctuation within the pipes.

2.1.2 Indirect Supply System

Figure 2: Indirect supply system simple installation schematic [2].

Indirect supply systems have a water storage tank in the vicinity of the building. Water from the supply mains of the water utility company is directed first and foremost to the water tank. Then, the pipes will supply the cold water fixtures via distribution pipes as shown in Figure 2.

This system is typically installed in most buildings in Malaysia. Due to the fact that all plumbing fixtures receive their water directly from the tank, they are all subject to a constant minimum pressure that varies with their distance from the tank. This solves the pressure fluctuation problem faced in the direct supply system.

The consistent pressure of a water tank storage system offers numerous benefits. Firstly, it reduces the cost of fittings since the pressure within the pipes can be accurately calculated. Moreover, when the water supply is interrupted, the large cistern will supply water for daily necessities.

All water tank sizing performed in Malaysia shall be based on the guide provided by Suruhanjaya Perkhidmatan Air Negara (SPAN) [1]. Indirect water supply systems in high rise buildings or bungalows may require hydro pneumatic pumps for the top 2-4 floors. Types of Storage Tanks

Figure 3: Polyethylene water tank [3].

Polyethylene tanks, as shown in Figure 3, are typically used in small residential houses. These range in size from 200 imperial gallons (igal) to 450 igal. There are also stainless steel water tanks used in residential houses.

Figure 4: Fibre Reinforced Plastic (FRP) water tank [4].

For medium-sized buildings, typically, Fibre Reinforced Plastic (FRP) tanks are used. FRP tanks are shown in Figure 4. These water tanks have the advantages of being UV resistant, are easy to install and do not corrode. And finally, for large buildings, concrete tanks with HDPE linings are used.

3. Hot Water Systems in Malaysia

For hot water supply systems, there are available options such as instant hot water and electric storage water heater for domestic usage. In Malaysia, recent technologies have also enabled air-conditioning heat pumps to be used to heat water.

3.1 Solar Water Heater in Malaysia

Figure 5: Solar water heater typical installation schematic [5].

Solar water heater systems are also available for domestic usage. A typical installation schematic is shown in Figure 5. Butarbutar et al. [6] recorded that it took about 7 hours for the water in the tank to heat up to approximately 60°C. The results were taken in Medan, Indonesia. At 8 a.m., the water was approximately 28°C. At around 3 p.m., the water rose to a usable temperature of approximately 60°C. This is shown in Figure 6.

Figure 6: Temperature of the water in the solar water heater tank by Butarbutar et al. [3].

Because of the long waiting period before hot water heats up, solar water heaters usually have electric heaters integrated into the system. On top of that, the sun does not always shine, therefore having a backup electric heater in the solar water heater system is crucial.

4. Pipe Material Selection

When it comes to pipe material selection for buildings, the material selected must not have any adverse health or safety effects to the building and its occupants.

When dealing with plastic pipes, there are abbreviations such as “PN 16” and “PN 20”. PN is the abbreviation for nominal pressure. Thus, a PN 16 pipe can withstand a pressure of 16 bar; meanwhile a PN 20 pipe can withstand a pressure of 20 bar.

Other terms such as “DN” represent the nominal diameter of a pipe. DN is the inside diameter of a pipe rounded off to the nearest integer.

4.1 Stainless Steel (SS)

Areas that are vulnerable to corrosion often use stainless steel pipes. Due to the high levels of moisture in coastal areas, stainless steel pipes are commonly used. Stainless steel pipes are resistant to corrosion because of the thin layer of chromium oxide within the core structure. Although stainless steel pipes are known to be resistant to corrosion, they are not resistant to all corrosion. Anaerobic and chloride corrosion can affect stainless steel pipes.

The most common stainless steel alloy is the food grade Stainless Steel 304 pipe. This pipe adds 18% chromium and 8% nickel to steel. SS 316 and 316L add molybdenum to minimise its vulnerability to chlorides.

Because stainless steel pipes have antimicrobial qualities that are excellent for conveying food products in processing systems, the food service industry makes the most of them.

In general, the 300 series stainless steel alloys are the most corrosion resistant and are non-magnetic. The 400 series is more ductile, abrasion resistant, can withstand higher temperatures and is magnetic. The 200 series alloys are used in sinks and applications where lower corrosion resistance is acceptable.

Below are the general advantages and disadvantages of Stainless Steel pipes.

Advantages of Stainless Steel pipes are:

  • Resistant to corrosion
  • Resistant to heat
  • Able to withstand high impact
  • Hygienic
  • Ease of manufacturing, installing and maintaining
  • Flexible with the option for custom shaped pipes and fittings

The disadvantages of Stainless Steel pipes include:

  • Expensive
  • SS 304 can corrode during welding

4.2. High Density Polyethylene (HDPE)

HDPE are plastic pipes that are usually coloured black with blue stripes. HDPE pipes are rugged and are typically used in outdoor piping.

When DN ≤ 63 mm, HDPE pipes adopt injection moulding hot-melt socket connection, also known as a hot-melt butt joint. However, when DN ≥ 75 mm, HDPE pipes adopt a hot-melt butt joint or electrofusion socket connection.

When connecting to different materials, HDPE pipes adopt flange or thread connection. Below are the general advantages and disadvantages of HDPE pipes.

Advantages of HDPE pipes are:

  • HDPE pipes are cheaper than PPR pipes
  • Non-toxic
  • Resistant to corrosion and rust
  • Resistant to internal microbial corrosion
  • Provides good water hammer resistance
  • Lightweight
  • Easy to install
  • Durable wear resistance
  • Long service life up to 50 years
  • Easy to recycle

Disadvantages of HDPE pipe comprise:

  • It cannot be used in hot water pipe networks
  • The price of fittings can be high
  • Hot melt welding requires high pressure and a long cooling time
  • Suffers from poor UV resistance. After long-term exposure to the sun, the HDPE pipe is prone to ageing and has a reduced service life

4.3. Polypropylene Random Copolymer (PPR)

PPR stands for Polypropylene Random Copolymer. Typically, in a building, PPR PN 16 pipes are used for domestic cold water supply, meanwhile, PPR PN 20 pipes are used for domestic hot water supply. This is because PPR PN 20 is able to withstand higher temperatures for prolonged periods. PPR pipes adopt injection moulding hot melt socket connection. The pipes are connected by flange or thread when connecting with different materials.

Below are the general advantages and disadvantages of PPR pipes.

Advantages of PPR pipes include:

  • Lightweight
  • Easy to install. It adopts a hot-melt connection and can complete a joint connection within a few seconds
  • Non-toxic
  • Resistant to corrosion and rust
  • Easy to recycle and is environmentally friendly
  • Long service life up to 50 years
  • Low resistance to flowing liquid
  • Can withstand hot water temperatures

Disadvantages of PPR pipes are:

  • Price is more expensive than other plastic pipes
  • Fragile and easy to fracture upon high impact
  • Few pipes and accessories available in the market
  • Pipe diameters are typically limited to DN 100Ø mm
  • The linear expansion coefficient of the pipe is large
  • Suffers from poor UV resistance. After long-term exposure to the sun, the PPR pipe is prone to ageing and has a reduced service life

5. Pipe Sizing Guide

Pipe sizing for cold water piping is based on the probability theory. The capacity of basins, sinks and other appliances varies. Draw-off tap sizes and flow rates differ between appliances. The frequency of use of appliances is different in different locations, both within and between buildings.

To solve this problem, loading units (LU) have been introduced to factor in appliance type, capacity, flow rate, period of use and frequency. Figure 7 shows the loading units for various frequency use cold water appliances [7].

Figure 7: Loading units based on frequency of usage [7].

Low use represents buildings with private facilities or small groups of persons. The time between each use is 1,200 seconds (20 minutes). Medium use consist of buildings with 600 seconds (10 minutes) between each use, such as low traffic public toilets.

Subsequently, high use represents 300 seconds (5 minutes) interval between each use. These are typically installed in theatres, cinemas, high traffic public toilets, places of worship, etc.

6. Our M&E Consultant Solutions

As M&E consultants, our solutions for Cold and Hot Water Systems include:

  • Cold and Hot Water system design
  • Cold and Hot Water system schematic
  • Transfer pump sizing
  • Hydro pneumatic pump sizing
  • Pipe loss calculation
  • Cold and hot water tank sizing

Perunding JW is an M&E Consulting firm based in Malaysia. If you are looking for more information or resources, reach out to our team of engineers. We will gladly assist you. Visit our homepage or call us at +603 7955 5918.


[1] Suruhanjaya Perkhidmatan Air Negara (SPAN), Unifrom Technical Guidelines Water Reticulation and Plumbing. Suruhanjaya Perkhidmatan Air Negara, 2018.

[2] Dolantethole, “Direct and Indirect Cold Water Systems,” 2012. (accessed Sep. 14, 2022).

[3] Conlex Enterprise Sdn Bhd, “Water Storage Solutions Malaysia.” (accessed Sep. 14, 2022).

[4] Potaglas Malaysia Sdn Bhd MALAYSIA SDN BHD, “Panel Tanks Manufacturer.” (accessed Sep. 14, 2022).

[5] U.S. Department of Energy, “Solar Water Heaters.” (accessed May 13, 2022).

[6] S. Butarbutar, I. Siregar, E. Y. Setiawan, and H. Ambarita, “Thermal characteristics of a flat-plate solar collector of hybrid solar water heater,” J. Phys. Conf. Ser., vol. 1116, no. 032007, 2018.

[7] P. Angus and A. Wilson, CIBSE Guide G: Public Health and plumbing engineering, 3rd ed. 2014. [Online].

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