SIZING WITH THE UNIFORM PLUMBING CODE

Sizing with data from the Uniform Plumbing Code is not too difficult. Allow me to give you some illustrations that are direct excerpts from the Uniform Plumbing Code. Look at the illustrations and try working through the sizing example that is provided (Fig. 3.1 through Fig. 3.17).

APPENDIX A

Because of the variable conditions encountered, it is impractical to lay down definite detailed rules of procedure for determining the sizes of water supply pipes in an appendix which must necessarily be limited in length. For a more adequate understanding of the problems involved, the reader is referred to Water-Distributing Systems for Buildings, Report BMS 79 of the National Bureau of Standards; and Plumbing Manual, Report BMS 66, also published by the National Bureau of Standards.

The following is a suggested order of procedure for sizing the water supply system.

A 1 Preliminary Information

A 1.1 Obtain the necessary information regarding the minimum daily service pressure in the area where the building is to be located.

A 1.2 If the building supply is to be metered, obtain information regarding friction loss relative to the rate of flow for meters in the range of sizes likely to be used. Friction-loss data can be obtained from most manufacturers of water meters. Friction losses for disk type meters may be obtained from Chart A-1.

CHART A-1

Friction Losses for Disk Type Water Meters

SIZING WITH THE UNIFORM PLUMBING CODE

A 1.3 Obtain all available local information regarding the use of different kinds of pipe with respect both to durability and to decrease in capacity with length of service in the particular water supply.

A 2 Demand Load

A 2.1 Estimate the supply demand for the building main and the principal branches and risers of the system by totaling the fixture units on each, Table A-2, and then by reading the corresponding ordinate from Chart A-2 or A-З, whichever is applicable.

A 2.2 Estimate continuous supply demands in gallons per minute (liters per second) for lawn sprinklers, air conditioners, etc., and add the sum to the total demand for fixtures. The result is the estimated supply demand of the building supply.

A 3 Permissible Friction Loss

A 3.1 Decide what is the desirable minimum pressure that should be maintained at the highest fixture in the supply system. If the highest group of fixtures contains flushometer valves, the pressure for the group should not be less than fifteen (15) psi (103.4kPa). For flush tank supplies, the available pressure may not be less than eight (8) psi (55.1 kPa).

A 3.2 Determine the elevation of the highest fixture or group of fixtures above the water (street) main. Multiply this difference in elevation by forty-three hundredths (0.43). The result is the loss in static pressure in psi (pounds per square inch) (kPa).

A 3.3 Subtract the sum of loss in static pressure and the pressure to be maintained at the highest fixture from the average minimum daily service pressure. The result will be the pressure available for friction loss in the supply pipes, if no water meter is used. If a meter is to be installed, the friction loss in the meter for the estimated maximum demand should also be subtracted from the service pressure to determine the pressure loss available for friction loss in the supply pipes.

TABLE A-2

Demand Weight of Fixtures in Fixture Units 1

Diameter of fitting	90° Stand ard	45° Stand ard	Stand ard	Coupling or Straight	Gate	Globe	Angle
(inches)	Elbow	Elbow	Tee 90Run of Tee Valve	Valve	Valve
	Feet	Feet	Feet	Feet	Feet	Feet	Feet
3/8	1	0.6	1.5	0.3	0.2	8	4
1/2	2	1.2	3	0.6	0.4	15	8
3/4	2.5	1.5	4	0.8	0.5	20	12
1	3	1.8	5	0.9	0.6	25	15
1-1/4	4	2.4	6	1.2	0.8	35	18
1-1/2	5	3	7	1.5	1	45	22
2	7	4	10	2	1.3	55	28
2-1/2	8	5	12	2.5	1.6	65	34
3	10	6	15	3	2	80	40
4	14	8	21	4	2.7	125	55
5	17	10	25	5	3.3	140	70
6	20	12	30	6	4	165	80

	TABLE A-3 (metric) Eauivalent Lenath of PiDe for Various Fittinas
	90°	4» U1 0		Coupling
Diameter	Stand-	Stand-	Stand-	or
of fitting	ard	ard	ard	Straight	Gate	Globe	Angle
(inches)	Elbow	Elbow	Tee 90° Run of Tee Valve	Valve	Valve
	m	m	m	m	m	m	m
9.5	0.3	0.2	0.5	0.1	0.1	2.4	1.2
12.7	0.6	0.4	0.9	0.2	0.1	4.6	2.4
19.1	0.8	0.5	1.2	0.2	0.2	6.1	3.6
25.4	0.9	0.5	1.5	0.3	0.2	7.6	4.6
31.8	1.2	0.7	1.8	0.4	0.2	10.6	5.5
38.1	1.5	0.9	2.1	0.5	0.3	13.7	6.7
50.8	2.1	1.2	3	0.6	0.4	16.7	8.5
63.5	2.4	1.5	3.6	0.8	0.5	19.8	10.3
76.2	3	1.8	4.6	0.9	0.6	24.3	12.2
101.6	4.3	2.4	6.4	1.2	0.8	38	16.7
127	5.2	3	7.6	1.5	1	42.6	21.3
152.4	6.1	3.6	9.1	1.8	1.2	50.2	24.3

* Allowances based on поп-recessed threaded fittings. Use one-half (1/2) the allowances for recessed threaded fittings or streamline solder fittings.

SIZING WITH THE UNIFORM PLUMBING CODE

A 3.4 Determine the developed length ot pipe from the water (street) main to the highest fixture. If close estimates are desired, compute with the aid of Table A-З the equivalent length of pipe for all fittings in the line from the water (street) main to the highest fixture and add the sum to the developed length. The pressure available for friction loss in pounds per square inch (kPa), divided by the developed lengths of pipe from the water (street) main to the highest fixture, times one hundred (100), will be the average permissible friction loss per one hundred (100) foot (30.4m) length of pipe.

A 4 Size of Building Supply

A 4.1 Knowing the permissible friction loss per one hundred (100 feet (30.4 m) of pipe and the total demand, the diameter of the building supply pipe may be obtained from Charts A-4, A-5, A-6, or A-7, whichever is applicable. The diameter of pipe on or next above the coordinate point corresponding to the estimated total demand and the permissible friction loss will be the size needed up to the first branch from the building supply pipe.

A 4.2 If copper tubing or brass pipe is to be used for the supply piping, and if the character of the water is such that only slight changes in the hydraulic characteristics may be expected, Chart A-4 may be used.

A 4.3 Chart A-5 should be used for ferrous pipe with only the most favorable water supply as regards corrosion and caking. If the water is hard or corrosive, Charts A-6 or A-7 will be applicable. For extremely hard water, it will be advisable to make additional allowances for the reduction of capacity of hot water lines in service.

A 5 Size of Principal Branches and Risers

A 5.1 The required size of branches and risers may be obtained in the same manner as the building supply by obtaining the demand load on each branch or riser and using the permissible friction loss computed in Section A 3.

A 5.2 Fixture branches to the building supply, if they are sized for the same permissible friction loss per one hundred (100) feet (30.4 m) of pipe as the branches and risers to the highest level in the building, may lead to inadequate water supply to the upper floor of a building. This may be controlled by: (1) selecting the sizes of pipe for the different branches so that the total friction loss in each lower branch is approximately equal to the total loss in the riser, including both friction loss and loss in static pressure; (2) throttling each such branch by means of a valve until the preceding balance is obtained; (3) increasing the size of the building supply and risers above the minimum required to meet the maximum permissible friction loss.

A 5.3 The size of branches and mains serving flushometer tanks shall be consistent with sizing procedures for flush tank water closets.

A 6 General

A 6.1 Velocities shall not exceed 10 ft/sec or the maximum values given in the appropriate Installation Standard, except as otherwise approved by the Administrative Authority.

A 6.2 If a pressure reducing valve is used in the building supply, the developed length of supply piping and the permissible friction loss should be computed from the building side of the valve.

A 6.3 The allowances in Table A-З for fittings are based on nonrecessed threaded fittings. For recessed threaded fittings and streamlined soldered fittings, one-half (1/2) the allowances given in the table will be ample.

A 7 Example

A 7.1 Assume an office building of four (4) stories and basement; pressure on the building side of the pressure reducing valve of fifty-five (55) psi (379 kPa) (after an allowance for reduced pressure "fall off” at peak demand); an elevation of highest fixture above the pressure reducing valve of forty-five (45) feet (13.7 m); a developed length of pipe from the pressure reducing valve to the most distant fixture of two hundred (200) feet (60.8 m); and fixtures to be installed with flush valves for water closets and stall urinals as follows:

Example

Fixture Units and Estimated Demands

Water Closets	130	1,300
Urinals	30	150
Shower Heads	12	48	12	12×4 x	3/4 = 36 (2.3 L/s)
Lavatories	130	260	130	130×2 x	3/4 = 195 (12.3 Us)
Service Sinks	27	108	27	27×4 x	3/4 = 81 5.1 Us)
Total		1,866	313 (19.7 L/s)	312	106 (6.7 Us)

Allowing for fifteen (15) psi (103.4 kPa) at the highest fixture under the maximum demand of three hundred and ten (310) gallons per minute (19.6 L/s), the pressure available for friction loss is found by the following:

SIZING WITH THE UNIFORM PLUMBING CODE

55 — [15 + (45 x 0.43)] = 20.65 psi
(metric) 379 — [103.4 + (13.7 x 9.8)] = 142.3 kPa

The allowable friction loss per one hundred (100) feet (30.4 m) of pipe is therefore:

100 x 20.65 + 200 = 10.32 psi
(metric) 30.4 x 142.3 + 60.8 = 71.1 kPa

If the pipe material and water supply are such that Chart A-5 applies, the required diameter of the building supply is three (3) inches (76.2 mm), and the required diameter of the branch to the hot water heater is two (2) inches (50.8 mm).

The sizes of the various branches and risers may be determined in the same manner as the size of the building supply or the branch to the hot water system by estimating the demand for the riser or branch from Charts A-2 or A-З, and applying the total demand estimate from the branch, riser or section thereof, to the appropriate flow chart.

FIGURE 3.7 ■ Sizing rules. (Courtesy of The Uniform Plumbing Code)

CHART A-2

Estimate Curves for Demand Load

300

400

joo

б200

too