🎯 Velocity vs. Target
📐 Pressure Drop
Sizing Breakdown
Full Calculation Table
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How to Use the Pipe Sizing Calculator
Choose copper Type L for most hydronic work, Type K for underground service lines, ACR copper for refrigerant lines, PEX for radiant and flexible runs, or steel Schedule 40 for larger mains.
Enter the design flow rate for this pipe segment and the velocity you want to design for. The 0.6 to 1.2 m/s default works for most branch piping in Canadian residential and light commercial systems.
Enter the equivalent length of this pipe run, including an allowance for fittings, so the pressure drop result reflects the actual circuit rather than just straight pipe.
Click Calculate Pipe Size to see the recommended nominal size, the actual velocity at that size, and the pressure drop over the entered length.
How to Size Pipe for Hydronic and Refrigerant Systems
Pipe sizing comes down to picking the smallest pipe that keeps velocity in a safe range for the application. Go too small and velocity climbs, which brings noise, erosion at fittings, and excessive pressure drop. Go too big and you waste money on pipe and fittings while risking sediment settling and poor heat transfer at low flow. This calculator works backward from your target velocity to find the nominal size that gets you there.
Choosing a Target Velocity
Canadian hydronic practice generally targets 0.6 to 1.2 m/s (2 to 4 ft/s) in branch circuits feeding individual zones or terminal units, and allows up to 2.4 m/s (8 ft/s) in distribution mains where some extra noise is acceptable and the pipe run is shorter relative to total flow. Domestic hot water recirculation lines often run lower, closer to 0.3 to 0.6 m/s, to manage erosion in copper over the system's service life. Use the flow velocity calculator to check an existing pipe size against these limits.
Copper, PEX, and Steel: Picking the Right Material
Type L copper is the standard for exposed hydronic piping in Canadian mechanical rooms because its wall thickness handles typical system pressures with margin. Type K, with an even thicker wall, mostly shows up in underground or below-slab service entrances. PEX tubing is common for radiant floor loops and concealed runs where its flexibility avoids extra fittings, but always check the manufacturer's pressure and temperature rating against your system's operating conditions. Refrigerant lines need ACR copper tubing rather than plumbing-grade copper, since ACR tube is cleaned, dehydrated, and capped to a different standard so it stays free of oxide and moisture that would contaminate a refrigerant circuit. The refrigerant line sizing calculator handles that sizing separately, since refrigerant lines also need a minimum vapour velocity to carry oil back to the compressor.
From Velocity to Pressure Drop
Once a pipe size meets your velocity target, the next check is pressure drop, since a long branch circuit at an acceptable velocity can still add up to a pump-sizing problem. This calculator estimates pressure drop using the Hazen-Williams method for water-based fluids, which is accurate enough for most hydronic design work. For a closer look at the underlying friction calculation, see the Hazen-Williams calculator or the more rigorous Darcy-Weisbach calculator, which is the better choice for refrigerant and glycol mixtures where fluid viscosity differs meaningfully from water.
Sizing the Whole Circuit
This tool sizes one pipe segment. A full hydronic design sums the pressure drop across every segment on the longest path, called the index circuit, to determine the total head a pump has to overcome. Once you have sized each segment, move to the pump head calculator to total the circuit, then the pump sizing calculator to select a circulator that meets both the flow and head requirement.
A Note on Accuracy
This calculator uses published nominal pipe dimensions and standard friction methods for estimating purposes. Actual pressure drop varies with fitting count, water temperature, and pipe age. For permit-stamped mechanical drawings or large commercial systems, confirm sizing against the current CSA B214 installation code and have a mechanical engineer verify the final design.
Frequently Asked Questions
Most Canadian hydronic designs target 0.6 to 1.2 m/s (2 to 4 ft/s) in branch piping and up to 2.4 m/s (8 ft/s) in mains. Staying inside this range keeps noise and erosion low while avoiding the stagnation and poor heat transfer that come with velocities under 0.3 m/s. Use the flow velocity calculator to check a size you already have in mind.
Type L copper is the standard choice for hydronic heating and cooling piping in Canadian mechanical systems, since it has a thicker wall than Type M and is rated for higher pressure than thin-wall options. Type K has an even thicker wall and shows up mostly in underground service lines. For refrigerant lines, use ACR copper tubing rather than plumbing-grade Type L or K, since ACR tube is cleaned and capped to a different standard for refrigerant compatibility.
The recommended nominal size depends only on flow rate and target velocity, so length does not change that result. What length does change is the pressure drop figure, since friction loss accumulates with distance. A longer equivalent length on the same pipe size will always show a higher total pressure drop, which is why long branch runs sometimes need a larger pipe even at the same flow rate, to keep total head manageable for the pump.
This tool is built around water-based hydronic flow and uses water's viscosity and density in its pressure drop estimate, so it is not accurate for refrigerant. Refrigerant lines also have a different sizing goal: suction lines need a minimum vapour velocity to carry compressor oil back to the unit, which is unrelated to the noise-and-erosion velocity target used here. Use the dedicated refrigerant line sizing calculator for liquid and suction line sizing instead.
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