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What is the maximum flow? Click Here

Common Household Pipe Types

PVC: Plastic pipe, most is white in color, some is gray, purple, or light brown. Pipe surface is firm and reasonably hard.

Steel: Gray or silver color, a magnet sticks to it. May be galvanized thus some times called "galvanized pipe".

Polyethylene: Black plastic, more flexible than PVC. Surface is softer, will scratch with fingernail.

Copper: Copper or green color metal. A magnet will not stick to it.

PEX: Plastic pipe, very similar to polyethylene, however it is not black, often red, white or blue color. Look for "PEX" printed on it.

Finding Pipe Size

Grab a piece of string about 6"(152mm) long, then find the location where your water supply pipe enters the house. Strip away any insulation, so you can get at the pipe and wrap the string around it. Measure how many inches of string it takes to go around the pipe once. Based on the string length use the table below to find your pipe size.

For Copper Pipe or PEX Pipe
1.96" (50mm) = 1/2" pipe
2.75" (70mm) = 3/4" pipe
3.53" (90mm) = 1" pipe
4.32" (110mm) = 1¼" pipe
5.10" (130mm) = 1½" pipe

For Steel Pipe or PVC Plastic Pipe
2.64" (67mm) = 1/2" Pipe
3.25" (83mm) = 3/4" pipe
4.00"(102mm) = 1" pipe
5.00"(127mm) = 1¼" pipe
6.00"(152mm) = 1½" pipe

For Flexible Polyethylene Pipe*
2.33-2.51" (59-64mm) = 1/2" pipe
2.96-3.33" (75-85mm) = 3/4" pipe
3.74-4.24" (95-108mm) = 1" pipe
4.90-5.57" (124-141mm) = 1¼" pipe
5.70-6.28" (145-160mm) = 1½" pipe

Your string length will vary a little, depending on such unavoidable variables as string stretch, dirt on pipe, manufacturing tolerance, what kind of mood you're in, etc..
*Polyethylene pipe size varies depending on the type of polyethylene pipe, thus a range of sizes.

Maximum Flow

Values are based on 7 feet per second of flow. This is the maximum recommended velocity for water in a pipe. Higher flows greatly increase the risk of water hammer, which can potentially damage the pipe.

WARNING: These values are the maximum safe flows that can be pushed through a pipe. The flows given are not an indication of how much water will be available from a given size of pipe. You should not use this table to determine what size a pipe should be, or how much water you can expect to get from it.

Pipe Size

Maximum Available GPM for a size of pipe.

SCH 40 PVC
or steel pipe

Polyethylene pipe

Type L copper pipe

PEX pipe

1/2"

7 GPM

6 GPM

5 GPM

3 GPM

5/8"

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7 GPM

7 GPM

3/4"

11 GPM

11 GPM

10 GPM

8 GPM

1"

18 GPM

18 GPM

18 GPM

12 GPM

1 1/4"

32 GPM

32 GPM

26 GPM

25 GPM

1 1/2"

44 GPM

44 GPM

38 GPM

35 GPM

2"

70 GPM

70 GPM

65 GPM

61 GPM

2 1/2"

100 GPM

100 GPM

100 GPM

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3"

150 GPM

150 GPM

140 GPM

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