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Pressure Loss Tables for Common Mainline Pipe & Tubing Types

 

Here are some pressure loss tables you can use to calculate the friction loss in your house or irrigation system mainline.  This is the old-school, low-tech method.  There are also free spreadsheets available (they use the free Open-Office spreadsheet program) on this website that will calculate pressure loss for you.  The spreadsheets cover more types and sizes of pipe than these tables.  I suggest using the spreadsheets, but these tables are handy if you want to do a quick look-up of a value, or just don’t do spreadsheets.

Quick background for those who linked to this page from a search for water pressure or something similar.  As water flows through a pipe it losses pressure.  The pressure is lost due to friction of the water against the pipe walls and also turbulence as the water tumbles around.  Knowing how much pressure loss to expect is important.  If there isn’t enough pressure left at the end of the pipe, then things like sprinklers, washing machines, dishwashers, faucets, toilets, etc. will not work.  For very general purposes, most of the fore-mentioned items need at least 20 PSI of pressure to operate.  Most will work much better at 30 PSI.

How To Use a Pipe Pressure Loss Table:

(PSI = pounds per square inch = lbs./sq.in.)

  • Select the proper table for the type of pipe, i.e.; SCH 40 PVC, SCH 40 steel, polyethylene, copper, etc.
  • Locate the proper column on the table for the pipe size.
  • Read down the column to the row for the flow rate (GPM) in the pipe section. You will find a PSI loss value (given as PSI/100).
  • Multiply the PSI loss value shown by the total length of the pipe section, then divide the product by 100. (PSI loss on these tables is given in PSI per 100 feet of pipe.)
  • Pressure loss values highlighted in yellow italics are over 5 feet per second. This is a high velocity, but considered acceptable for short distances (less than 50 feet of pipe length.)
  • Pressure losses greater than those shown on the chart can cause permanent and expensive damage to your plumbing. You must use a lower flow (GPM) in the pipe.

PSI Loss Value x Length of Pipe / 100 = PSI loss in pipe

Example: 1″ size, type SCH 40 PVC mainline. The length of the mainline pipe is 23 feet. The water flow rate through the mainline is 18 GPM. Using a pipe pressure loss table we find that the PSI loss for 1″ SCH 40 PVC at a flow rate of 18 GPM is 8.12 PSI per 100′. Therefore:   8.12 x 23 / 100 = 1.87 PSI – to simplify, you can round up the value to 2 PSI loss

(Note: PSI loss charts vary somewhat from each other. Other charts may result in an answer slightly different from the one in this example.)

PRESSURE LOSS TABLE FOR SCH 40 PVC PIPE

FLOW GPM 3/4″ 1″ 1 1/4″ 1 1/2″ 2″ 2 1/2″ 3″
1 0.13 0.04 0.01 —— —— —— ——
2 0.45 0.14 0.04 —— —— —— ——
3 0.95 0.30 0.08 —— —— —— ——
4 1.62 0.50 0.14 0.07 —— —— ——
5 2.45 0.76 0.20 0.10 —— —— ——
6 3.44 1.06 0.28 0.13 —— —— ——
7 4.57 1.42 0.38 0.18 —— —— ——
8 5.85 1.81 0.48 0.23 —— —— ——
9 7.28 2.25 0.60 0.28 0.09 —— ——
10 8.85 2.74 0.72 0.34 0.11 —— ——
11 10.56 3.26 0.86 0.41 0.12 —— ——
12 —— 3.84 1.01 0.48 0.14 —— ——
13 —— 4.45 1.17 0.56 0.17 —— ——
14 —— 5.10 1.35 0.64 0.19 —— ——
FLOW GPM 3/4″ 1″ 1 1/4″ 1 1/2″ 2″ 2 1/2″ 3″
15 —— 5.80 1.53 0.72 0.22 0.09 ——
16 —— 6.53 1.72 0.82 0.25 0.11 ——
18 —— 8.12 2.14 1.01 0.30 0.13 ——
20 —— —— 2.60 1.23 0.37 0.16 ——
22 —— —— 3.10 1.47 0.44 0.19 ——
24 —— —— 3.65 1.72 0.51 0.21 0.08
26 —— —— 4.23 2.00 0.60 0.25 0.09
28 —— —— 4.85 2.29 0.68 0.29 0.10
30 —— —— 5.51 2.60 0.78 0.33 0.12
35 —— —— —— 3.46 1.03 0.44 0.15
40 —— —— —— 4.43 1.32 0.54 0.20
45 —— —— —— —— 1.64 0.69 0.24
50 —— —— —— —— 1.99 0.84 0.30
55 —— —— —— —— 2.37 1.00 0.35
60 —— —— —— —— 2.79 1.18 0.41
FLOW GPM 3/4″ 1″ 1 1/4″ 1 1/2″ 2″ 2 1/2″ 3″
65 —— —— —— —— 3.23 1.36 0.48
70 —— —— —— —— 3.71 1.56 0.55
75 —— —— —— —— —— 1.78 0.62
80 —— —— —— —— —— 2.00 0.70
85 —— —— —— —— —— 2.24 0.78
90 —— —— —— —— —— 2.49 0.87
95 —— —— —— —— —— 2.75 0.96
100 —— —— —— —— —— 3.02 1.05
110 —— —— —— —— —— —— 1.26
120 —— —— —— —— —— —— 1.47
130 —— —— —— —— —— —— 1.71
140 —— —— —— —— —— —— 1.96
150 —— —— —— —— —— —— 2.23
160 —— —— —— —— —— —— 2.51
FLOW GPM 3/4″ 1″ 1 1/4″ 1 1/2″ 2″ 2 1/2″ 3″

Pressure losses highlighted in yellow italics reflect flow velocity between 5 and 7 feet/second. Use care utilizing flow velocities in this range. Water hammer damage can result from a combination of high pressure and high velocity. Pressure losses shown are in PSI per 100 feet of pipe length.


PRESSURE LOSS TABLE, POLYETHYLENE PIPE

For SDR-7,  SDR-9,  SDR 11.5,  and SDR 15  (all have the same inside diameter)

Flow in GPM 3/4″ 1″ 1 1/4″ 1 1/2″ 2″
1  GPM 0.12 0.04 0.01 0.00 0.00
2  GPM 0.45 0.14 0.04 0.02 0.01
3  GPM 0.95 0.29 0.08 0.04 0.01
4  GPM 1.62 0.50 0.13 0.06 0.02
5  GPM 2.44 0.76 0.20 0.09 0.03
6  GPM 3.43 1.06 0.28 0.13 0.04
7  GPM 4.56 1.41 0.37 0.18 0.05
8  GPM 5.84 1.80 0.47 0.22 0.07
9  GPM 7.26 2.24 0.59 0.28 0.08
10  GPM 8.82 2.73 0.72 0.34 0.10
3/4″ 1″ 1 1/4″ 1 1/2″ 2″
11  GPM 10.53 3.25 0.86 0.40 0.12
12  GPM 12.37 3.82 1.01 0.48 0.14
13  GPM 13.34 4.43 1.17 0.55 0.16
14  GPM 16.45 5.08 1.34 0.63 0.19
15  GPM 18.70 5.78 1.52 0.72 0.21
16  GPM 21.07 6.51 1.71 0.81 0.24
17  GPM 23.57 7.28 1.92 0.91 0.27
18  GPM 26.21 8.10 2.13 1.01 0.30
19  GPM 28.97 8.95 2.36 1.11 0.33
20  GPM 31.85 9.84 2.59 1.22 0.36
3/4″ 1″ 1 1/4″ 1 1/2″ 2″
22  GPM 38.00 11.74 3.09 1.46 0.43
24  GPM 44.65 13.79 3.63 1.72 0.51
26  GPM 51.78 16.00 4.21 1.99 0.59
28  GPM 59.40 18.35 4.83 2.28 0.68
30  GPM 67.50 20.85 5.49 2.59 0.77
32  GPM 76.06 23.5 6.19 2.92 0.87
34  GPM 26.29 6.92 3.27 0.97
36  GPM 29.22 7.69 3.63 1.08
38  GPM 32.30 8.50 4.02 1.19
40  GPM 35.52 9.35 4.42 1.31
3/4″ 1″ 1 1/4″ 1 1/2″ 2″
42  GPM 38.88 10.24 4.83 1.43
44  GPM 42.43 11.16 5.27 1.56
46  GPM 46.01 12.12 5.72 1.70
48  GPM 49.79 13.11 6.19 1.84
50  GPM 53.70 14.14 6.68 1.98
55  GPM 16.87 7.97 2.36
60  GPM 19.82 9.36 2.77
65  GPM 22.98 10.86 3.22
70  GPM 26.36 12.45 3.69
75 GPM 29.96 14.15 4.19

Pressure losses highlighted in yellow italics reflect flow velocity between 5 and 7 feet/second. Use care utilizing flow velocities in this range. Water hammer damage can result from a combination of high pressure and high velocity. Pressure losses shown are in PSI per 100 feet of pipe length.


Pressure Loss Table, Type K Copper Pipe or Tubing

Type K copper pipe has the thickest wall and highest pressure ratings of the common copper tubing types. In order of wall thickness, common copper tubing types are Type M (thinnest), Type L, and Type K (thickest). Type L is commonly used for household plumbing. Type K is most often used to make short threaded-end nipples.  If you don’t know what Type the pipe is, assume it is Type K.

Flow in GPM 1/2″ 3/4″ 1″ 1 1/4″
1  GPM 1.20 0.23 0.05 0.02
2  GPM 4.33 0.77 0.18 0.06
3  GPM 9.17 1.65 0.38 0.13
4  GPM 15.67 2.78 0.68 0.22
5  GPM 4.21 1.02 0.33
6  GPM 5.90 1.44 0.46
7  GPM 7.84 1.90 0.61
8  GPM 10.03 2.46 0.78
9  GPM 12.48 3.03 0.97
10  GPM 15.15 3.68 1.18
11  GPM 4.40 1.41
12  GPM 5.17 1.66
13  GPM 6.00 1.93
14  GPM 6.88 2.21
15  GPM 7.81 2.51
16  GPM 8.42 2.83
17  GPM 9.42 3.16
18  GPM 3.52
19  GPM 3.89
20  GPM 4.28
22  GPM 5.10
24  GPM 5.99
26 GPM 6.95

Pressure losses highlighted in yellow italics reflect flow velocity between 5 and 7 feet/second. Use care utilizing flow velocities in this range. Water hammer damage can result from a combination of high pressure and high velocity. Pressure losses shown are in PSI per 100 feet of pipe length.


PRESSURE LOSS TABLE, TYPE L COPPER PIPE OR TUBING

Type L copper tube is the type most commonly used for household plumbing. In order of wall thickness, common copper tubing types are Type M (thinnest), Type L, and Type K (thickest). If you don’t know what Type the pipe is, assume it is Type K.

Flow in GPM 1/2″ 3/4″ 1″ 1 1/4″
1  GPM 0.95 0.16 0.04 0.02
2  GPM 3.44 0.57 0.15 0.06
3  GPM 7.29 1.20 0.33 0.12
4  GPM 12.41 2.05 0.56 0.20
5  GPM 18.77 3.09 0.85 0.30
6  GPM 4.34 1.18 0.43
7  GPM 5.77 1.58 0.57
8  GPM 7.39 2.02 0.72
9  GPM 9.19 2.51 0.90
10  GPM 11.17 3.05 1.10
11  GPM 3.64 1.31
12  GPM 4.28 1.54
13  GPM 4.96 1.78
14  GPM 5.69 2.04
15  GPM 6.46 2.32
16  GPM 7.28 2.62
17  GPM 8.15 2.93
18  GPM 9.06 3.25
19  GPM 3.60
20  GPM 3.96
22  GPM 4.72
24  GPM 5.55
26 GPM 6.43

Pressure losses highlighted in yellow italics reflect flow velocity between 5 and 7 feet/second. Use care utilizing flow velocities in this range. Water hammer damage can result from a combination of high pressure and high velocity. Pressure losses shown are in PSI per 100 feet of pipe length.



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