1-1/2" Diameter (38.1 mm) Flow Area: 1.767 sq in Standard Capacity: 27.54 GPM @ 5 ft/s Cold Max: 44.07 GPM @ 8 ft/s

1-1/2" Pipe Flow Rate & GPM Capacity Calculator

A standard 1-1/2" inside diameter pipe carries 27.54 GPM (104.26 Liters/min) at standard design velocity (5 ft/s) and up to 44.07 GPM at maximum allowable cold water velocity (8 ft/s). Part of our master Pipe Flow Rate Calculator and Copper Flow Rate suite.

Presets:

Pipe Material Specification

Inside Diameter (ID) Required

Fluid Velocity (v) Required

Desired Flow Rate (Q) Required

Primary Output Unit

Calculated Result

Flow Delivery

Estimated Flow Rate (Q)

27.54 US Gallons / min (GPM)

≈ 104.25 L/min

Your pipe with an internal diameter of 1.50 inches has a cross-sectional area of 1.767 in² (1,140.09 mm²). At a fluid velocity of 5.00 ft/s, the volumetric flow rate is 27.54 GPM.

Flow Rate Conversions

US Gallons / min 27.54 GPM

Litres / min 104.25 L/min

Litres / sec 1.737 L/s

Cubic Feet / min 3.682 CFM

Cubic Metres / hr 6.255 m³/h

Cubic Metres / sec 0.0017 m³/s

Internal Flow Area 1.767 in² (1140.1 mm²)

Fluid Velocity 5.00 ft/s (1.52 m/s)

Flow results depend on internal pipe diameter and velocity. For actual installations, consider system head loss and friction fittings.

Hydraulic Capacity Matrix

1-1/2" Pipe Flow Rate vs. Velocity Chart

Volumetric water flow in US Gallons per Minute (GPM), Liters per Minute, and Liters per Second across fluid velocities (1 to 12 ft/s).

Velocity (ft/s)	Flow Rate (GPM)	Liters / Min (L/min)	Liters / Sec (L/s)	Cubic Ft / Sec (cfs)	Hydraulic Status
1 ft/s	5.51 GPM	20.9 L/min	0.348 L/s	0.0123 cfs	✓ Quiet / Hot Water Safe
2 ft/s	11.02 GPM	41.7 L/min	0.695 L/s	0.0246 cfs	✓ Quiet / Hot Water Safe
3 ft/s	16.52 GPM	62.5 L/min	1.042 L/s	0.0368 cfs	✓ Quiet / Hot Water Safe
4 ft/s	22.03 GPM	83.4 L/min	1.390 L/s	0.0491 cfs	✓ Quiet / Hot Water Safe
5 ft/s	27.54 GPM	104.3 L/min	1.738 L/s	0.0614 cfs	✓ Design Standard (5 ft/s)
6 ft/s	33.05 GPM	125.1 L/min	2.085 L/s	0.0736 cfs	⚠ Cold Water Max (8 ft/s)
7 ft/s	38.56 GPM	146.0 L/min	2.433 L/s	0.0859 cfs	⚠ Cold Water Max (8 ft/s)
8 ft/s	44.06 GPM	166.8 L/min	2.780 L/s	0.0982 cfs	⚠ Cold Water Max (8 ft/s)
10 ft/s	55.08 GPM	208.5 L/min	3.475 L/s	0.1227 cfs	⛔ High Velocity / Erosive
12 ft/s	66.10 GPM	250.2 L/min	4.170 L/s	0.1473 cfs	⛔ High Velocity / Erosive

Mathematical Derivation

How to Calculate 1-1/2" Pipe Flow Rate

Volumetric continuity equation $Q = A \times v$ applied to circular pipes.

Step 1

Calculate Internal Area ($A$)

Compute circular cross-sectional area in square inches:

A = \pi \times (0.75)^2 = 1.7671 sq in

Step 2

Convert Area to Square Feet

Divide square inches by 144:

A_sqft = 1.7671 / 144 = 0.01227 sq ft

Step 3

Apply Continuity (Q = A × v)

Multiply area by design velocity (v = 5 ft/s):

Q_cfs = 0.01227 \times 5 = 0.0614 cfs

Step 4

Convert CFS to US GPM

Multiply cubic feet per second by 448.831 (GPM conversion factor):

Q_gpm = 0.0614 \times 448.83 = 27.54 GPM

Engineering Guidelines

1-1/2" Pipe Velocity & Hydraulic Guidelines

Noise thresholds, maximum fixture capacities, and erosion limits.

Design Flow Rate (5 ft/s)
27.54 GPM
104.26 Liters/min

Max Cold Water Flow (8 ft/s)

44.07 GPM

Peak demand limit

Hot Water Limit (4-5 ft/s)

22.03 - 27.54 GPM

CDA erosion threshold

Internal Cross Section

1.767 in²

1.5 inch ID

Common Hydraulic Applications for 1-1/2" Piping:

Commercial building water headers
Swimming pool suction and return lines
Central hydronic heating primary loops
Multi-riser apartment feeds

Trade Hydraulic Advisory: Standard diameter for high-flow swimming pool filtration circulation systems (requiring 30-50 GPM) and commercial hydronic headers.

Diameter Navigation

Compare Flow Capacities of Other Pipe Sizes

Explore volumetric GPM capacities across other plumbing supply and main line diameters.

← Smaller Pipe 1-1/4" Pipe Flow Rate Master Engine Pipe Flow Rate Calculator Larger Pipe → 2" Pipe Flow Rate

Expert FAQ Guide

1-1/2" Pipe Flow Rate FAQs

Engineering questions and velocity guidelines for 1-1/2" piping.

2 Questions Answered

Q1 How many GPM flows through a 1-1/2" pool pipe?

For pool suction and return plumbing at standard 6-8 ft/s velocity, a 1-1/2" pipe delivers 33 to 44 GPM (maximum recommended flow for typical residential pool pumps).

Q2 How many GPM can a 1-1/2" water pipe handle at 5 ft/s?

At 5 ft/s velocity, a 1-1/2" pipe delivers 27.54 GPM (104.26 Liters/min).

Flow Delivery

Flow Rate Conversions

1-1/2" Pipe Flow Rate vs. Velocity Chart

How to Calculate 1-1/2" Pipe Flow Rate

Calculate Internal Area ($A$)

Convert Area to Square Feet

Apply Continuity (Q = A × v)

Convert CFS to US GPM

1-1/2" Pipe Velocity & Hydraulic Guidelines

Common Hydraulic Applications for 1-1/2" Piping:

Compare Flow Capacities of Other Pipe Sizes

1-1/2" Pipe Flow Rate FAQs

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