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    Pipe Thread Size Page


     

    Pipe Thread Size (NPT) does not refer to the outside (OD) physical dimension of a pipe or hose. The hose diameter cannot be used as an indication of the thread size on the hose connector fitting. To determine pipe thread size (NPT), measure outside diameter (male threads) or inside diameter (female threads) and then use table below to determine pipe thread size

    Measure the outside diameter (O.D.) of the fitting's thread at the very end, round to the closest reference measurement below and note the corresponding NPT size.

    Nominal Thread Size (NPT)
    1/8"
    1/4"
    3/8"
    1/2"
    3/4"
    1"
    Actual O.D. Measurement
    3/8"
    1/2"
    5/8"
    3/4"
    1"
    1-3/8"

    FPT

    MPT

    M22 - Twist

    Measure the inside diameter of thread at "A"; Find figure nearest this dimension in column 2 or 3 of chart. The dimension in column 1 will be your nominal pipe thread size.

    Measure the outside diameter of the large portion of the thread at "B"; Find figure nearest this dimension in column 2 or 3 of chart. The dimension in column 1 will be your nominal pipe thread size.

    This is a picture of a 22 mm twist connector. There are 2 types used on pressure washers. The most common has a 14 mm seal cone.

     "C" seal cone = 14 mm
     "C" seal cone = 15 mm

     

     

    Column 1

    Column 2

    Column 3

    Pipe Thread Size

    Approx. (fraction) Inch. 

    Actual (decimal) Inch.

    1/8

    13/32

    .405

    1/4

    35/64

    .540

    3/8

    43/64

    .675

    1/2

    27/32

    .840

    3/4

    1-3/64

    1.050

    1

    1-5/16

    1.315

    1-1/4

    1-21/32

    1.660

    1-1/2

    1-29/32

    1.900

    Metric Size
    Twist Coupler

     

     

    14 mm

    17/32

    .531

    15 mm

    19/32

    .594

    22 mm

    27/32

    .844