Essay Mechanical and Electrical Systems
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SizingWaterSupplyPiping.ppsPowerPoint® Presentation
Chapter 5-*
PowerPoint® Presentation
Chapter 5
Sizing Water Supply Piping
Available Water Pressure • Fixture Demand • Type and Length of Piping • Height of Building • Flow Pressure Needed at Top Floor • Sizing Water Supply Piping
Chapter 5-*
A pressure-reducing valve converts high and/or fluctuating inlet water pressure to a lower or constant outlet pressure.
Chapter 5-*
The available pressure is the water pressure in the street water main or other supply source. Common street water main pressure is 45 psi–60 psi. Water pressure within a building must never be allowed to exceed 80 psi. If the street water main pressure exceeds 80 psi, a pressure-reducing valve must be installed on the water service at the point where the pipe enters the building. See Figure 5-1. A pressure-reducing valve is an automatic device used to convert high and/or fluctuating inlet water pres-sure to a lower or constant outlet pressure. When street water main pressure fluctuates widely throughout the day, the water supply system of the building must be designed on the basis of the minimum pressure available.
Minimum flow rates for fixtures and appliances must be considered when designing water supply systems.
Chapter 5-*
Each plumbing fixture served by the water supply system has a specified flow rate. Flow rate is the volume of water used by a fixture in a given amount of time. Flow rate is measured in gallons per minute (gpm). See Figure 5-2. The total demand on a water supply system if all fixtures are used simultaneously is determined by adding the minimum flow rates for all the plumbing fixtures within a building. However, all plumbing fixtures in a building are rarely used simultaneously.
Each water supply piping material has a different resistance to water flow within the tube, pipe, and tubing.
Chapter 5-*
Pressure loss due to friction occurs in all water supply piping due to the resistance resulting from water contacting the interior pipe surface and resistance between water molecules. Galvanized pipe, copper tube, and PVC, CPVC, and PEX plastic pipe and tubing are used to convey water to fixtures. Each material has a different resistance to water flow within the tube, pipe, and tubing. See Figure 5-3.
Flow resistance occurs as water passes through valves, fittings, and changes in direction of piping.
Chapter 5-*
Flow resistance also occurs as water passes through valves, fittings, and changes in direction. Pressure loss due to friction increases as more pipe, fittings, valves, and other devices are installed in the water supply system. See Figure 5-4. As pressure loss within water supply piping increases, the discharge capacity of fixture supply pipes decreases. When designing a water supply piping system, pressure loss due to friction must be considered so that adequate water pressure is available at the outlet and proper plumbing fixture and appliance operation is ensured.
Flow pressure is the water pressure in the water supply pipe near an outlet and is measured while the outlet is wide open and flowing.
Chapter 5-*
Every plumbing fixture requires a minimum flow pressure to function properly. Flow pressure, or working water pressure, is the water pressure in the water supply pipe near an outlet, such as a faucet, and is measured while the outlet is wide open and flowing. Flow pressure ranges from 8 psi for faucets and tank-type water closets to 25 psi for certain models of flushometer valves. See Figure 5-5.
The fixture supply pipe for three fixtures or fewer in the same bathroom of a house is a minimum of 1/2″ size.
Chapter 5-*
As a general rule, and based on the available pressure, demand, type and length of piping, height of the building, and flow pressure needed at the top floor, the minimum sizes for water supply piping for 1/2 pipe are:
- minimum size of concealed water supply piping
- minimum size for three fixtures or less in the same bathroom of a house. See Figure 5-6.
- minimum size of fixture branch pipe, except individual fixture branch pipe for specified fixtures and appliances. See Figure 5-7.
The minimum size of fixture branch pipe is 1/2″.
Chapter 5-*
As a general rule, and based on the available pressure, demand, type and length of piping, height of the building, and flow pressure needed at the top floor, the minimum sizes for water supply piping for 1/2 pipe are:
- minimum size of concealed water supply piping
- minimum size for three fixtures or less in the same bathroom of a house. See Figure 5-6.
- minimum size of fixture branch pipe, except individual fixture branch pipe for specified fixtures and appliances. See Figure 5-7.
A typical one-story, one-family dwelling contains a laundry tray, clothes washer, and water heater in the basement.
Chapter 5-*
Plumbers generally design plumbing systems for residential structures. See Figure 5-8. In a typical one-story, one-family dwelling, a laundry tray, clothes washer, and water heater may be located in the basement. A kitchen sink, water closet, lavatory, and bathtub are installed on the first floor. Two sillcocks are also installed—one on the left side of the house and one at the rear.
The cwsfu demand for an entire building is determined by adding the wsfu demand of individual fixtures if the building does not include water closets fitted with flushometer valves.
Chapter 5-*
Water supply piping sizing for larger installations is based on the available water pressure, fixture demand, type and length of piping, height of the building, and flow pressure needed at the top floor. The water supply fixture unit sizing method is a common method of properly sizing water supply piping for buildings that require a 2″ or smaller water service and in which the distribution piping does not exceed 2 1/2″ in size. Water supply piping sizing for installations requiring larger pipe sizes should be completed by a mechanical engineer. The procedure for sizing water supply piping is:
1. Determine the total demand on the water supply piping. When determining the total cold water supply fixture unit (cwsfu) demand, either step 1A or step 1B will be used.
- For buildings with water closets that are not fitted with flushometer valves, total the cwsfu demand for the entire building by adding the wsfu demand of individual fixtures. See Figure 5-9.
…Complete procedural listing on pages 98 – 101.
Water meter, water service, main, and branch pipe sizes are based on the available pressure, length of water supply piping, and wsfu demand.
Chapter 5-*
The procedure for sizing water supply piping is:
- Determine the total demand on the water supply piping. When determining the total cold water supply fixture unit (cwsfu) demand, either step 1A or step 1B will be used.
- Determine the developed length of piping from the water meter to the most remote outlet if the water pressure at the meter is known, or from the water main to the most remote outlet if the water pressure at the meter is unknown.
- Determine pressure loss due to height by identifying the difference in head (elevation) between the water meter (or other water supply source) and highest water supply outlet and multiplying the difference by 0.5 psi.
- Determine the working water pressure by sub-tracting the pressure loss due to height from the available water pressure.
- Select the pressure range from the Water Supply Pipe and Water Meter Sizes for Water Supply Systems table that includes the pressure value determined in step 4. See Figure 5-10.
…Complete procedural listing on pages 98 – 101.
Cold water supply pipe sizing for a four-unit apartment building starts at the most remote water outlet.
Chapter 5-*
The procedure for sizing the water supply piping for a common four-unit, multifamily dwelling is:
- Determine the total demand on the water supply piping in cwsfu and hwsfu. See Figure 5-11. Step 1B is omitted since the building is not equipped with flushometer valves.
…Complete procedural listing on pages 101 – 104.
Hot water supply pipe sizing for a four-unit apartment building starts at the hot water supply outlet that is farthest from the water heater.
Chapter 5-*
…Complete procedural listing on pages 101 – 104.
12. The hot water supply piping is sized using the same column of the Water Supply Pipe and Water Meter Sizes for Water Supply Systems table as was used to size the cold water supply piping. The sizing of the hot water supply piping starts at the hot water supply outlet that is farthest from the water heater—apartment 1, in the application example—and is sized back toward the heater. See Figure 5-12. The three fixtures in this apartment that require a hot water supply—kitchen sink, lavatory, and bathtub—are properly served by 1/2″ fixture branch and fixture supply pipes. The hot water piping for the other three apartments is sized similarly using 1/2″ pipe.
Cold water supply pipe sizing for a public building starts with determining the total demand on the water supply piping.
Chapter 5-*
The procedure for sizing the water supply piping for a public building is:
1. Determine the total demand on the water supply piping in cwsfu and hwsfu. See
Figure 5-13.
…Complete procedural listing on pages 106 – 108.
The hot water supply pipe sizing for a public building begins at the fixture farthest from the water heater.
Chapter 5-*
…Complete procedural listing on pages 106 – 108.
12. The hot water supply pipe sizing begins at the fixtures farthest from the water heater, which are the women’s rest room lavatories. See Figure 5-14. The lavatories are served by 1/2″ fixture supply and fixture branch pipes. The fixture branch pipe size is increased to 3/4″ with a 1/2″ × 1/2″× 3/4″ tee at the point where the hot water supplies for the lavatories join together, rated at 8 hwsfu demand.
Chapter 5-*
Chapter 5-*
Chapter 5-*
The available pressure is the water pressure in the street water main or other supply source. Common street water main pressure is 45 psi–60 psi. Water pressure within a building must never be allowed to exceed 80 psi. If the street water main pressure exceeds 80 psi, a pressure-reducing valve must be installed on the water service at the point where the pipe enters the building. See Figure 5-1. A pressure-reducing valve is an automatic device used to convert high and/or fluctuating inlet water pres-sure to a lower or constant outlet pressure. When street water main pressure fluctuates widely throughout the day, the water supply system of the building must be designed on the basis of the minimum pressure available.
Chapter 5-*
Each plumbing fixture served by the water supply system has a specified flow rate. Flow rate is the volume of water used by a fixture in a given amount of time. Flow rate is measured in gallons per minute (gpm). See Figure 5-2. The total demand on a water supply system if all fixtures are used simultaneously is determined by adding the minimum flow rates for all the plumbing fixtures within a building. However, all plumbing fixtures in a building are rarely used simultaneously.
Chapter 5-*
Pressure loss due to friction occurs in all water supply piping due to the resistance resulting from water contacting the interior pipe surface and resistance between water molecules. Galvanized pipe, copper tube, and PVC, CPVC, and PEX plastic pipe and tubing are used to convey water to fixtures. Each material has a different resistance to water flow within the tube, pipe, and tubing. See Figure 5-3.
Chapter 5-*
Flow resistance also occurs as water passes through valves, fittings, and changes in direction. Pressure loss due to friction increases as more pipe, fittings, valves, and other devices are installed in the water supply system. See Figure 5-4. As pressure loss within water supply piping increases, the discharge capacity of fixture supply pipes decreases. When designing a water supply piping system, pressure loss due to friction must be considered so that adequate water pressure is available at the outlet and proper plumbing fixture and appliance operation is ensured.
Chapter 5-*
Every plumbing fixture requires a minimum flow pressure to function properly. Flow pressure, or working water pressure, is the water pressure in the water supply pipe near an outlet, such as a faucet, and is measured while the outlet is wide open and flowing. Flow pressure ranges from 8 psi for faucets and tank-type water closets to 25 psi for certain models of flushometer valves. See Figure 5-5.
Chapter 5-*
As a general rule, and based on the available pressure, demand, type and length of piping, height of the building, and flow pressure needed at the top floor, the minimum sizes for water supply piping for 1/2 pipe are:
- minimum size of concealed water supply piping
- minimum size for three fixtures or less in the same bathroom of a house. See Figure 5-6.
- minimum size of fixture branch pipe, except individual fixture branch pipe for specified fixtures and appliances. See Figure 5-7.
Chapter 5-*
As a general rule, and based on the available pressure, demand, type and length of piping, height of the building, and flow pressure needed at the top floor, the minimum sizes for water supply piping for 1/2 pipe are:
- minimum size of concealed water supply piping
- minimum size for three fixtures or less in the same bathroom of a house. See Figure 5-6.
- minimum size of fixture branch pipe, except individual fixture branch pipe for specified fixtures and appliances. See Figure 5-7.
Chapter 5-*
Plumbers generally design plumbing systems for residential structures. See Figure 5-8. In a typical one-story, one-family dwelling, a laundry tray, clothes washer, and water heater may be located in the basement. A kitchen sink, water closet, lavatory, and bathtub are installed on the first floor. Two sillcocks are also installed—one on the left side of the house and one at the rear.
Chapter 5-*
Water supply piping sizing for larger installations is based on the available water pressure, fixture demand, type and length of piping, height of the building, and flow pressure needed at the top floor. The water supply fixture unit sizing method is a common method of properly sizing water supply piping for buildings that require a 2″ or smaller water service and in which the distribution piping does not exceed 2 1/2″ in size. Water supply piping sizing for installations requiring larger pipe sizes should be completed by a mechanical engineer. The procedure for sizing water supply piping is:
1. Determine the total demand on the water supply piping. When determining the total cold water supply fixture unit (cwsfu) demand, either step 1A or step 1B will be used.
- For buildings with water closets that are not fitted with flushometer valves, total the cwsfu demand for the entire building by adding the wsfu demand of individual fixtures. See Figure 5-9.
…Complete procedural listing on pages 98 – 101.
Chapter 5-*
The procedure for sizing water supply piping is:
- Determine the total demand on the water supply piping. When determining the total cold water supply fixture unit (cwsfu) demand, either step 1A or step 1B will be used.
- Determine the developed length of piping from the water meter to the most remote outlet if the water pressure at the meter is known, or from the water main to the most remote outlet if the water pressure at the meter is unknown.
- Determine pressure loss due to height by identifying the difference in head (elevation) between the water meter (or other water supply source) and highest water supply outlet and multiplying the difference by 0.5 psi.
- Determine the working water pressure by sub-tracting the pressure loss due to height from the available water pressure.
- Select the pressure range from the Water Supply Pipe and Water Meter Sizes for Water Supply Systems table that includes the pressure value determined in step 4. See Figure 5-10.
…Complete procedural listing on pages 98 – 101.
Chapter 5-*
The procedure for sizing the water supply piping for a common four-unit, multifamily dwelling is:
- Determine the total demand on the water supply piping in cwsfu and hwsfu. See Figure 5-11. Step 1B is omitted since the building is not equipped with flushometer valves.
…Complete procedural listing on pages 101 – 104.
Chapter 5-*
…Complete procedural listing on pages 101 – 104.
12. The hot water supply piping is sized using the same column of the Water Supply Pipe and Water Meter Sizes for Water Supply Systems table as was used to size the cold water supply piping. The sizing of the hot water supply piping starts at the hot water supply outlet that is farthest from the water heater—apartment 1, in the application example—and is sized back toward the heater. See Figure 5-12. The three fixtures in this apartment that require a hot water supply—kitchen sink, lavatory, and bathtub—are properly served by 1/2″ fixture branch and fixture supply pipes. The hot water piping for the other three apartments is sized similarly using 1/2″ pipe.
Chapter 5-*
The procedure for sizing the water supply piping for a public building is:
1. Determine the total demand on the water supply piping in cwsfu and hwsfu. See
Figure 5-13.
…Complete procedural listing on pages 106 – 108.
Chapter 5-*
…Complete procedural listing on pages 106 – 108.
12. The hot water supply pipe sizing begins at the fixtures farthest from the water heater, which are the women’s rest room lavatories. See Figure 5-14. The lavatories are served by 1/2″ fixture supply and fixture branch pipes. The fixture branch pipe size is increased to 3/4″ with a 1/2″ × 1/2″× 3/4″ tee at the point where the hot water supplies for the lavatories join together, rated at 8 hwsfu demand.
