// CODE SNIPPET
A104.0 Permissible Friction Loss
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Decide what is the desirable
minimum residual pressure that shall be maintained at the
highest fixture in the supply system. Where the highest group
of fixtures contains flushometer valves, the residual pressure
for the group shall be not less than 15 pounds-force per square
inch (psi) (103 kPa). For flush tank supplies, the available
residual pressure shall be not less than 8 psi (55 kPa).
Determine the elevation of the highest
fixture or group of fixtures above the water (street) main.
Multiply this difference in elevation by 0.43. The result is the loss of static pressure in psi (kPa).
Subtract the sum of loss in
static pressure and the residual 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, where no water meter is used. Where
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.
Determine the developed
length of pipe from the water (street) main to the highest fixture.
Where close estimates are desired, compute with the aid
of Table A104.4(1), Table A104.4(2), or Table A104.4(3),
whichever is applicable, the equivalent length of pipe for 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 psi (kPa), divided by the
developed lengths of pipe from the water (street) main to the
highest fixture, times 100, will be the average permissible
friction loss per 100 feet (30480 mm) length of pipe.
For SI units: 1 inch = 25 mm, 1 foot = 304.8 mm, 1 degree = 0.017 rad
* Allowances are based on nonrecessed threaded fittings. Use one-half the allowances for recessed threaded fittings or streamlined solder fittings.
For SI units: 1 inch = 25 mm, 1 foot = 304.8 mm
For SI units: 1 inch = 25 mm, 1 foot = 304.8 mm
| DIAMETER OF FITTING (inches) | 90° STANDARD ELBOW (feet) | 45° STANDARD ELBOW (feet) | 90° STANDARD TEE (feet) | COUPLING OR STRAIGHT RUN OF TEE (feet) | GATE VALVE (feet) | GLOBE VALVE (feet) | ANGLE VALVE (feet) |
|---|---|---|---|---|---|---|---|
| 3/8 | 1.0 | 0.6 | 1.5 | 0.3 | 0.2 | 8 | 4 |
| 1/2 | 2.0 | 1.2 | 3.0 | 0.6 | 0.4 | 15 | 8 |
| 3/4 | 2.5 | 1.5 | 4.0 | 0.8 | 0.5 | 20 | 12 |
| 1 | 3.0 | 1.8 | 5.0 | 0.9 | 0.6 | 25 | 15 |
| 11/4 | 4.0 | 2.4 | 6.0 | 1.2 | 0.8 | 35 | 18 |
| 11/2 | 5.0 | 3.0 | 7.0 | 1.5 | 1.0 | 45 | 22 |
| 2 | 7.0 | 4.0 | 10.0 | 2.0 | 1.3 | 55 | 28 |
| 21/2 | 8.0 | 5.0 | 12.0 | 2.5 | 1.6 | 65 | 34 |
| 3 | 10.0 | 6.0 | 15.0 | 3.0 | 2.0 | 80 | 40 |
| 4 | 14.0 | 8.0 | 21.0 | 4.0 | 2.7 | 125 | 55 |
| 5 | 17.0 | 10.0 | 25.0 | 5.0 | 3.3 | 140 | 70 |
| 6 | 20.0 | 12.0 | 30.0 | 6.0 | 4.0 | 165 | 80 |
* Allowances are based on nonrecessed threaded fittings. Use one-half the allowances for recessed threaded fittings or streamlined solder fittings.
| DIAMETER OF FITTING (inches) | 90 DEGREE ELBOW (feet) | 45 DEGREE ELBOW (feet) | COUPLING OR STRAIGHT RUN OF TEE (feet) | 90 DEGREE STANDARD TEE (feet) |
|---|---|---|---|---|
| 1/2 | 1.6 | 0.8 | 1.0 | 3.1 |
| 3/4 | 2.1 | 1.1 | 1.4 | 4.1 |
| 1 | 2.6 | 1.4 | 1.7 | 5.3 |
| 11/4 | 3.5 | 1.8 | 2.3 | 6.9 |
| 11/2 | 4.0 | 2.1 | 2.7 | 8.1 |
| 2 | 5.2 | 2.8 | 3.5 | 10.3 |
| DIAMETER OF FITTING (inches) | 90 DEGREE ELBOW (feet) | 45 DEGREE ELBOW (feet) | COUPLING OR STRAIGHT RUN OF TEE (feet) | 90 DEGREE STANDARD TEE (feet) |
|---|---|---|---|---|
| 1/2 | 1.5 | 0.8 | 1.0 | 4.0 |
| 3/4 | 2.0 | 1.1 | 1.4 | 5.0 |
| 1 | 2.5 | 1.4 | 1.7 | 6.0 |
| 11/4 | 3.8 | 1.8 | 2.3 | 7.0 |
| 11/2 | 4.0 | 2.1 | 2.7 | 8.0 |
| 2 | 5.7 | 2.6 | 4.3 | 12.0 |