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:

Impact Force 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.

diagram


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

Formula for reaction force

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.)

Torque Formula

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?

Example formula

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

If you have any questions regarding hose and pipe pressure loss calculations please call our Customer Service Line at Toll Free 866-858-4982 or send us an email at: info@ultimatewasher.com

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)