Pressure Loss Through Hose, Pipe and due to Height
Pressure Loss due to height - Telescoping Wand Application
It takes pressure to lift water to a height, so if a spray gun is at a higher elevation than the outlet of the pressure washer, a modest amount of pressure is lost in lifting the water. The chart below gives the amount of pressure loss and it is independent of system pressure, flow rate and hose size.
| Elevation of Gun Above Pressure Washer (in FT) | Pressure Loss due to Elevation (in PSI) |
0 |
0 |
10 |
4 |
20 |
9 |
30 |
13 |
40 |
17 |
50 |
22 |
100 |
43 |
200 |
87 |
Impact, Reaction Force, and Torque for Bent Wands
The impact force of water spray from a straight wand, which is equal to the reaction force against the person holding the gun/wand, is given by this formula:
The impact force is proportional to the square root of the pressure, so to double the impact force requires four times the pressure.
For a bent wand, two forces act on the operator: reaction force pushing back on the operator (F1 in the diagram), and a force due to the bend that acts to "lift" the wand (F2 in the diagram). The "lifting" force acts on the operator as a torque.
Calculating Reaction Force and Torque for a Bent Wand :
Where :
F= Impact Force (lb)
F1= Reaction Force on operator (lb)
a= angle of wand bent
cos= cosine
gpm= gallons per minute
psi= pounds per square inch
Where:
F= Impact force (lb)
F2= "Lifting" force on wand (lb)
a= angle of wand bent
sin= sine
L= length from trigger to nozzle (ft.)
Example: What are the force and a torque at the gun for a nozzle running 8gpm at 2500psi, with a wand bent 15 degrees that measures 36 in. from trigger to nozzle?
Caution: All of the foregoing formulas allow precise calculations, but the results are nonetheless approximate, because pf many variables in an actual system.
Mar 2012 - Cleaner Times Magazine / IWA
Hose Pressure Loss (per 100 ft of Hose)
The pressure loss is determined by the total amount of water flow produced by the pressure washer. Pressure loss does not depend on the operating pressure of the unit. The chart below presents the measurement of 100 FT long hose. The pressure loss for other hose lengths is calculated proportionally to that length (100FT). For instance, 50 FT of hose will have 1/2 of the amount of loss and 200 FT of hose will have double the loss of the amount shown in the chart. There are several other factors that may cause pressure loss such as hose liner ID tolerance, hose inner liner smoothness, manner in which the hose is laid out during use, type of fittings on each end, and sometimes the temperature of the water. Pressure loss will also decrease if the hose is positioned up hill. However, these factors are not as essential and were not taken into consideration in these calculations.
|
Hose Friction Pressure Loss
(Pressure Drop in PSI per 100FT of Hose with Typical Water Flow Rates) |
|||||||
| WATER FLOW GPM | Hose Inside Diameters, Inches | ||||||
1/4"
|
5/16" |
3/8" |
1/2" |
5/8" | 3/4" | 1" | |
| 1 | 54 | 20 | 7 | 2 | - | - | - |
| 2 | 180 | 60 | 25 | 6 | 2 | - | - |
| 3 | 380 | 120 | 50 | 13 | 4 | 2 | - |
| 4 | - | 220 | 90 | 24 | 7 | 3 | - |
| 5 | - | 320 | 130 | 34 | 10 | 4 | - |
| 6 | - | - | 220 | 52 | 16 | 7 | 1 |
| 8 | - | - | 300 | 80 | 25 | 10 | 2 |
| 10 | - | - | - | 120 | 38 | 14 | 3 |
| 15 | - | - | - | 250 | 80 | 30 | 7 |
| 20 | - | - | - | - | 121 | 50 | 12 |
| 25 | - | - | - | - | 200 | 76 | 19 |
| 40 | - | - | - | - | 410 | 162 | 42 |
| 60 | - | - | - | - | - | 370 | 93 |
Water Line Pressure Loss
| (Pressure Drop In PSI Per 100FT) | ||||||||||||||||||||
| GPM | Steel Pipe (Normal Diameter) | Brass Pipe (Normal Diameter) | Copper Tubing OD Type L | |||||||||||||||||
| 1/4" | 3/8" | 1/2" | 3/4" | 1" | 1-1/4" | 1-1/2" | 1/4" | 3/8" | 1/2" | 3/4" | 1" | 1-1/4" | 1-1/2" | 1/4" | 3/8" | 1/2" | 5/8" | 3/4" | 7/8" | |
| 1 | 8.5 | 1.9 | - | - | - | - | - | 6 | 1.6 | - | - | - | - | - | 120 | 13 | 2.9 | 1 | - | - |
| 2 | 30 | 7 | 2.1 | - | - | - | - | 20 | 5.6 | 1.8 | - | - | - | - | 400 | 45 | 10 | 3.4 | 1.3 | - |
| 3 | 60 | 14 | 4.5 | 1.1 | - | - | - | 40 | 11 | 3.6 | - | - | - | - | - | 94 | 20 | 6.7 | 2.6 | - |
| 5 | 150 | 36 | 12 | 2.8 | - | - | - | 100 | 28 | 9 | 2.2 | - | - | - | - | 230 | 50 | 17 | 6.1 | 30 |
| 8 | 330 | 86 | 28 | 6.7 | 1.9 | - | - | 220 | 62 | 21 | 52 | 1.6 | - | - | - | 500 | 120 | 40 | 15 | 6.5 |
| 10 | 520 | 130 | 43 | 10 | 3 | - | - | 320 | 90 | 30 | 7.8 | 2.4 | - | - | - | - | 180 | 56 | 22 | 10 |
| 15 | - | 270 | 90 | 21 | 6.2 | 1.6 | - | - | 190 | 62 | 16 | 5 | 1.5 | - | - | - | - | 120 | 44 | 20 |
| 25 | - | 670 | 240 | 56 | 16 | 4.2 | 2 | - | 470 | 150 | 40 | 12 | 3.8 | 1.7 | - | - | - | 330 | 110 | 50 |
| 40 | - | - | - | - | 66 | 17 | 8 | - | - | - | - | 39 | 11 | 5 | - | - | - | 550 | 200 | 88 |
| 60 | - | - | - | - | - | 37 | 17 | - | - | - | - | - | 23 | 11 | - | - | - | - | - | - |
| 80 | - | - | - | - | - | 52 | 29 | - | - | - | - | - | 40 | 19 | - | - | - | - | - | - |
| 100 | - | - | - | - | 210 | 107 | 48 | - | - | - | - | - | 61 | 28 | - | - | - | - | - | - |
Pipe Pressure Loss
The values in the chart below present the approximate calculations since the pipe pressure loss can be affected by other factors, including water temperature, pipe ID tolerance, type of fittings, and pipe inner wall smoothness. In addition, schedule 40 and schedule 80 pipes have different IDs and, therefore, different pressure losses.
WATER FLOW GPM |
PRESSURE LOSS, PSI
|
|
1/2" STEEL PIPE
|
1/2" PVC PIPE |
|
1 |
1
|
1
|
2 |
4
|
4
|
3 |
8 |
9
|
4 |
14
|
15
|
5 |
21
|
23
|
6 |
30
|
32
|
8 |
52
|
56
|
10 |
80
|
87 |
Friction Loss in Pipe Fittings in Equivalent Feet of Pipe
| FITTING | FITTING SIZE | ||||||
1/2" |
3/4" |
1" |
1-1/4" |
1-1/2" |
2" |
2-1/2" |
|
| 90° Std Elbow | 1.6 |
2.1 |
2.6 |
3.5 |
4 |
5.5 |
6.2 |
| 90° Long Elbow | 1 |
1.4 |
1.7 |
2.3 |
2.7 |
4.3 |
5.1 |
| 90° Street Elbow | 3 |
3.4 |
4.4 |
5.8 |
6.7 |
8.6 |
10.3 |
| 45° Std Elbow | 0.8 |
1.1 |
1.4 |
1.8 |
2.1 |
2.8 |
3.3 |
| 45° Street Elbow | 1 |
1.8 |
2.3 |
3 |
3.5 |
4.5 |
5.4 |
| Square Elbow | 3 |
3.9 |
5 |
6.5 |
7.6 |
9.8 |
11.7 |
| Std Tee Straight Run | 1 |
1.4 |
1.7 |
2.3 |
2.7 |
4.3 |
5.1 |
| Std Tee Branch Run | 4 |
5.1 |
6 |
6.9 |
8.1 |
12 |
14.3 |
| Gate Valve - Full Open | 0.7 |
0.9 |
1.1 |
1.5 |
1.7 |
2.2 |
2.7 |
Helpful Conversions
Volume & Weight
| Gal | X |
3.785 |
= Liters |
| Gal | X |
128 |
= Ounces |
| Gal | X |
231 |
= Cubic Inches |
| Gal | X |
8.3453 |
= Pounds |
| Ltr | X |
61.02 |
= Cubic Inches |
| Ltr | X |
33.82 |
= Ounces |
| Ltr | X |
.2642 |
= Gallons |
| Ltr | X |
1000 |
= CM2 |
| ML (CC) | X |
.0338 |
= Ounces |
| Gram | X |
.03527 |
= Ounces |
| PSI | X |
.0689 |
= Bar |
| Bar | X |
14.5 |
= PSI |
| In. HG | X |
.4912 |
= PSI |
| In. H2O | X |
.8226 |
= In. HG |
Horsepower
GPM x PSI 1457 |
= Elec. Brake HP |
GPM x PSI 1714 |
= Hydraulic HP |
GPM x PSI 1100 |
= Gasoline HP (industrial grade) |
GPM x PSI 900 |
= Gasoline HP (standard grade) |
GPM x PSI 1457 |
= Elec. Brake HP |
GPM x PSI 1714 |
= Hydraulic HP |
GPM x PSI 1100 |
= Gasoline HP (industrial grade) |
GPM x PSI 900 |
= Gasoline HP (standard grade) |
