Kitchen Faucet Supply Line Sizes (Explained!)

There are a plethora of different types of faucet supply lines, often known as water supply lines.

Water is supplied to a faucet through two 1/2″ water pipes that enter the cabinet beneath the sink. The pipe on the left transports hot water, while the pipe on the right transports cold water. A set of water valves, typically angle stop valves, connects the two pipes.

The type of angle stop and manner of installation is determined by the type of pipe. The discharge ports on the majority of valves are 3/8-inch compression threads. Two 1/2-inch male pipe-thread—1/2 NPT—intake ports are standard on a faucet. 

Faucet Supply Line

What Size Are Kitchen Faucet Supply Lines?

The main pipes that connect to the main water supply are normally 3/4 inch in diameter. Branch lines that feed individual fixtures are typically 1/2 inch in diameter.

The conventional pipes that comprise a home water supply system are normally measured in two major diameters; however, this might vary based on the valves and accessories that comprise the system.

A faucet supply line comprises two primary diameters of copper, galvanized steel, or PEX pipes. The main pipes, which connect the main water supply to the water heater, are 3/4 inch in diameter. The branch lines, which feed individual fixtures, have a diameter of 1/2 inch.

The 1/2-inch supply pipes that lead to the sink each have a shutdown valve, which is one of two considerations that decide the connector size on the faucet hose.

The intake must be a 1/2-inch female pipe thread (FPT) connector for galvanized pipes, a 1/2-inch compression or sweat connector for copper pipes, or a 1/2-inch barbed connector for PEX pipes. However, if you’re installing a faucet, you’re more interested in the outlet port.

Female connectors on faucet supply hoses might be one of three types:

  • 1/2-inch slip joint (SJ), so named because it contains an insert that slips into the male connector to provide a watertight connection.
  • It has a 1/2-inch outer diameter (OD) and is identical to an SJ fitting except that it does not have an insert.
  • 3/8-inch OD fitting, which is the same as a 1/2-inch OD fitting but smaller.

How To Determine Faucet Supply Line Size?

Remove all of the pipe’s insulation. Wrap a 6″ length of thread (or a cloth tape measure) around the pipe once and measure to the nearest 1/8 of an inch. Once you’ve determined the circumference, use the chart below to determine the size of your faucet supply line.

The string method (which measures the circumference of the supply line) is probably the best approach to estimate the diameter of your faucet supply line. The circumference is the distance required to go once around the pipe.

Remove all of the pipe’s insulation. Wrap a 6″ length of thread (or a cloth tape measure) around the pipe once and measure to the nearest 1/8 of an inch…

Copper Pipe or PEX tubingSteel Pipe or PVC Plastic PipeFlexible (usually black) Polyethylene Pipe
2.75″ (70mm) = 3/4″ pipe3.25″ (83mm) = 3/4″ pipe2.96-3.33″ (75-85mm) = 3/4″ pipe
3.53″ (90mm) = 1″ pipe4.00″(102mm) = 1″ pipe3.74-4.24″ (95-108mm) = 1″ pipe
4.32″ (110mm) = 1 1/4″ pipe5.00″(127mm) = 1 1/4″ pipe4.90-5.57″ (124-141mm) = 1 1/4″ pipe
5.10″ (130mm) = 1 1/2″ pipe6.00″(152mm) = 1 1/2″ pipe5.70-6.28″ (145-160mm) = 1 1/2″ pipe

The faucet supply line is measured in nominal sizes rather than real dimensions, which might be perplexing.

3/4-inch copper pipe, for example, does not measure 3/4-inch. Type M pipe has an outer diameter (OD) of 0.875 inches and an inner diameter (ID) of 0.811 inches (a designation that relates to wall thickness).

Standard Schedule 40 galvanized steel 3/4-inch pipe has an OD of 1.050 inches and an ID of 0.824 inches (also a wall thickness designation).

To make matters more complicated, tubing sizes, such as the small-diameter plastic or copper tubing used to connect icemakers, represent the real exterior diameter. Still, hose sizes indicate the actual internal diameter.

Another method is to look for manufacturer’s markings printed on plastic, copper, and cast iron supply line.

What Size are Kitchen Faucet Connections?

Although faucet connectors aren’t standardized, the majority of them use 1/2-inch male pipe thread connectors.

The hoses that link the valves to the faucet have a 1/2-inch diameter and are available in a variety of lengths as well as 3/8- and 1/2-inch female connection types, so you can always find one that suits both your valves and your faucet.

Measuring the Size of Faucet Connection

It can be difficult to determine what size faucet connection you require. The “pipe size” actually refers to what is known as “nominal diameter.”

Fittings might be perplexing. Their internal diameters must be large enough to fit over the outside diameter of the pipe. For example, a half-inch plastic elbow has an outside diameter of around 1-1/4 inches.

Actual Diameter to Nominal Diameter Conversion

The simplest way to determine the nominal faucet connection size you require is to follow these procedures and consult the conversion chart below.

For Male Threads

  1. Take an outside diameter (OD) measurement of your pipe or pipe fitting:
  • Wrap a piece of yarn around the pipe.
  • Make a mark at the spot where the string meets.
  • Determine the length between the tip of the string and the mark you created using a ruler or measuring tape (circumference)
  • Divide the circumference divided by 3.14159
  1. Determine the nominal diameter using the chart below.

For Female Threads

  1. Take an inside diameter (ID) measurement of your pipe or pipe fitting (use a ruler or tape measure).
  1. Determine the nominal diameter using the chart below.

Nominal Diameter Conversion Chart (All Measurements in Inches)

Outside or Inside DiameterDecimal EquivalentNominal DiameterTypical Threads Per Inch
5/160.3131/1627
13/320.4051/827
35/640.5401/418
43/640.6753/818
27/320.8401/214
1-3/64 1.0503/414
1-5/161.315111 ½ 
1-21/321.6601 ¼ 11 ½ 
1-29/321.9001 ½ 11 ½ 
2-3/82.375211 ½ 
2-7/82.8752 ½ 8
3-1/23.50038
44.0003 ½ 8
4-1/24.50048

Are Kitchen Faucets Universal Size?

No. Unless otherwise specified in the specification, conventional faucet hole sizes for kitchens are 1 3/8′′ (1.375 Inches or 34.925 mm) in diameter. However, the size of faucet holes varies depending on the make and model.

There are many different kitchen faucets, and there is no universally accepted size for faucet holes. Because a kitchen sink installation can be a haven, but it won’t help you if you don’t know what faucet to use and, as a result, what hole size to use.

Standard sizes vary depending on the type of faucet you intend to install. There will be no mistakes or inconveniences if you first measure the faucet size and then drill the hole per that measurement.

Still, the ideal faucet hole size can be referred to as a standard size. As a result, the normal width for your kitchen faucet is 1 3/8 inches. But there is also variety. Some kitchen faucets, however, require a 1 1/2-inch wide hole.

That is now the normal size. However, a decent faucet normally has only one hole, whereas kitchen faucets installed with a plate or a large/small bowl require three holes in total.

The first thing you should remember is that the size of your faucet determines the hole size. Assume you’re captivated by a gorgeous faucet that’s broader than your kitchen faucet hole.

Suppose the hole size is normal 1 3/8. It won’t fit. What happens if you acquire a faucet that is smaller than the hole on your kitchen faucet? Water will eventually leak from the opening and may flood your kitchen.

Bottom Line

Flexible plastic and braided metal are the two most popular materials used to make faucet supply hoses.

Metal ones survive longer, especially when used with hot water, but they are a little more expensive. Corrugated copper was formerly popular, but you rarely see it under sinks nowadays because it becomes rigid and leaks as it ages.

Other water supply line types may be visible under the sink, depending on the accessories that come with your faucet.

The supplementary hoses that connect the faucet diverter to the sprayer or, if the faucet is a wide variety, to the handles are typically 1/2 inch in diameter as well. However, they feature proprietary quick-connect fittings that vary by manufacturer.

A water purifier can be linked to the water supply using 1/4- or 3/8-inch copper tubing.