How to calculate quantity of pipes in water distribution system?
Answers
Answer:
Pipes for water distribution in a building are available in various sizes. Determination of suitable pipe sizes for various purposes in a building based on various factors such as cost, pressure etc. are discussed.
Explanation:
Draw all suggested horizontal mains, risers and branch lines with necessary information includes types and number of fixtures and flow that is needed.
Calculate fixtures demand weight employing Table 1 and Table 2.
Specify water demand in gallon per millimeter using Figure 2 and Figure 3 and total number of fixture units.
Estimate equivalent length of the pipe for each stack in the system. This step should start from the street main.
Determine average minimum pressure in the street main. This can be obtained from Water Company or by test.
Specify minimum pressure required for the highest fixture
Calculate the loss of pressure in the pipes using the computed equivalent length of the pipe.
Finally, select the size of the pipe using Figure 4.
Note:
Unit sizes provided in the table 1 and table 2 is in mm, but the size of pipes in the chart is in inch. 1 inch= 25.4mm, 1 ft. = 304.8mm, 1 gallon/m=3.785L/m.
Water velocity should not be greater than 2.438m/s at valve seat to prevent noise and erosion. So, Pipe area should be at least equal to water flow rate divided by eight.
Sizes for fixture supply pipes provided in table 1 and table 2 are minimums.
Table-1: Fixture Units, Trap and Connection Sizes for Plumbing Fixtures for Domestic Waters
Types of fixture Domestic water
Fixture-unit value as load factors Minimum size of connections, mm
Private Public Hot water Cold water
Bathtub (with or without overhead shower 2 4 12.7 12.7
Bidet
Combination sink and tray 3 – 12.7 12.7
Combination unit and tray with food disposal unit 4
Dental unit 1 9.525
Dental lavatory 1 2 12.7 12.7
Dish water, domestic 2
Drinking fountain 1 2 9.525
Floor drains 1
Kitchen sink 2 4 12.7 12.7
Kitchen sink, domestic, with food waste grinder 3
Lavatory 1 19.05 9.525
Lavatory 2 12.7 12.7
Lavatory, barber, beauty parlor 2
Lavatory, surgeon’s 2
Laundry tray (1 or 2 compartments) 2 4 12.7 12.7
Shower, per head 2 4 12.7 12.7
Sinks Surgeon’s 3 12.7 12.7
Sinks Flushing rim (with valve) 2 19.05 19.05
Sinks Service (trap standard) 3 12.7 12.7
Sinks Service (P trap) 2 4 12.7 12.7
Sinks Pot, scullery, 4
Urinal, pedestal, siphon jet, blowout 10 25.4
Urinal, wall lip 5 12.7
Urinal stall 5 50.8 19.05
Urinal with flush tank 3
Wash sink (circular or multiple) each set of faucets 2 12.7 12.7
Water closet, tank-operated 3 5 19.05
Water closet, valve-operated 6 10 25.4
Table-2: Fixture Units, Trap and Connection Sizes for Plumbing Fixtures for Drainage
Types of fixture Drainage
Fixture-unit value as load factors Minimum size of trap, mm
Bathtub (with or without overhead shower 2 38.1
Bidet
Combination sink and tray 2
Combination unit and tray with food disposal unit 3
Dental unit 1 31.75
Dental lavatory 2
Dish water, domestic 2 38.1
Drinking fountain 1 31.75
Floor drains 2 50.8
Kitchen sink 2 or 3 38.1
Kitchen sink, domestic, with food waste grinder 2
Lavatory 1 31.75
Lavatory 2 38.1
Lavatory, barber, beauty parlor 2
Lavatory, surgeon’s 2
Laundry tray (1 or 2 compartments) 2
Shower, per head 2 50.8
Sinks Surgeon’s 3 38.1
Sinks Flushing rim (with valve) 6 76.2
Sinks Service (trap standard) 3
Sinks Service (P trap) 3 50.8
Sinks Pot, scullery, 3 38.1
Urinal, pedestal, siphon jet, blowout 6 76.2
Urinal, wall lip 2 38.1
Urinal stall 2 50.8
Urinal with flush tank 2 38.1
Wash sink (circular or multiple) each set of faucets 3
Water closet, tank-operated 4 76.2
Water closet, valve-operated 6
Domestic Water Demand Curve
Fig.2: Domestic Water Demand Curve Specify Rate of Flow Using the Number of Fixture Units Served
Domestic Water Demand Curve
Fig.3: Domestic Water Curve, Enlarged Portion for Low Water Demand
Determination of flow in copper tubing and other pipes
Fig.4: Determination of flow in copper tubing and other pipes that will be smoothed after service of 15 to 20 years