MODULE 8 Plumbing Equipment and Systems
The calculation examples are shown in an accordion-style display. Some questions are accompanied by equations and/or tables for quick reference. Solve the problem on your own and then click on the question to view the solution. This will help you make sense of the work as you read through the problem-solving process.
1.
A light commercial building is installed with four flush tank type water closets, two urinals with flushometers, and four lavatories. What is the total water supply fixture units (wsfu)? What is the probable water demand?
Water closets: (4) WC x 5 wsfu 20
Urinals: (2) UR x 5 wsfu 10
Lavatories: (4) LV x 2 wsfu 8
Total WSFU 38
From Table 8-3B, the probable water demand is 55 gpm.
2.
What is the pressure at the base of a water pipe feeding a plumbing facility 500 feet above the base due to static height alone?
The water column equivalent is 1 psi = 2.31 feet. With a water column of 600 feet, the static pressure at the base of the column (pipe) is: 500 ft 2.31 = 216 psi.
3.
If the roof area is 1500 sq. ft., and the roof is adjacent to three vertical walls of 100, 200 and 500 sq. ft. each. What shall the roof drain or drains be designed for?
The equivalent projected roof area plus 35% of the two largest vertical adjacent walls which are 500 and 200 sq. ft. respectively. The equivalent area is:
1500 + 0.35 × 700 = 1745 sq. ft.
Note that not all codes are consistent on this calculation.
4.
A building is installed with 300 tons of air conditioning. The air conditioning unit is water cooled through a cooling tower. How much make-up water should be provided?
Based on 0.35 gpmton, the makeup water rate is: 300 tons × 0.35 gpmton = 10.5 gpm.
5.
What is the pressure at the base of a water pipe feeding a plumbing facility 500 feet above the base due to static height alone?
The water column equivalent is 1 psi = 2.31 feet. With a water column of 600 feet, the static pressure at the base of the column (pipe) is: 500 feet2.31 = 216 psi.
6.
What is the minimum number of roof drains for any size building? For a building over 10,000 sq. ft. of roof area?
The minimum roof drains for any roof is 2, and that for buildings over 10,000 sq. ft. is 4.
7.
What size horizontal storm drain pipe should be installed for a building having 16,000 sq. ft. of projected roof area, in a region having 2-inch rainfall rate, and the drain pipe is laid with 116”/ft. slope? With 14”/ft. slope?
There should be a minimum of 4 roof drains, assuming each carries 14th of the storm water of 4000 sq. ft.
Each drain pipe shall be minimum 5-inch diameter at 116” slope and 4” diameter at 14” slope.
8.
What is the maximum number of fixture units (dfu) that may be connected to a 4-in. drain line with 14 in. per foot slope?
A maximum of 840 dfu’s may be connected to the line.